Drinking water tests

What is Clostridium Perfringens? 
Clostridium Perfringens is a bacterium that can live in the water supply for a long time and is an indicator of previous contamination events. Drinking water should be free from Clostridium Perfringens. Clostridium Perfringens is a spore forming microorganism. Its spores are particularly resistant to unfavourable conditions in the environment and thus they survive for long periods. As such they can be useful indicators of water that is intermittently polluted. In the Drinking Water Regulations it is defined as an Indicator parameter.

What is a Clostridium Perfringens exceedance? 
A drinking water exceedance is a result from a drinking water sample which is above the acceptable limit. The limit for Clostridium Perfringens is 0 per 100ml, therefore any result that is greater than this is seen as a Clostridium Perfringens exceedance.

What can cause a Clostridium Perfringens exceedance? 
Exceedances for Clostridium Perfringens can occur following a contamination incident or from a failure in the treatment process to remove or inactivate it.

How are exceedances of Clostridium Perfringens dealt with? 
All exceedances for Clostridium Perfringens are notified to the HSE and Uisce Éireann consults with them to seek their advice in relation to the protection of public health. Clostridium Perfringens exceedances are also notified to the EPA where there may be a risk to public health, or where the exceedance indicates a persistent issue. Clostridium Perfringens exceedances are fully investigated to determine the cause and corrective actions are taken to ensure the water supply is adequately disinfected.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Colony Count? 
Colony Count is a test for naturally occurring environmental bacteria found in soil, air and water. During the water treatment process the Colony Count is kept as low as possible. If large numbers are detected it indicates whether the water treatment system is effective. The parameter is a good indicator of the cleanliness of the water infrastructure and reveals how suitable the water is in the manufacture of food and drink products where high counts may lead to spoilage. In the Drinking Water Regulations it is defined as Indicator parameter.

What is an exceedance of Colony Count?  
The EU drinking water directive does not specify a limit for this parameter, however it does specify that no abnormal change should occur. The usefulness of this parameter is that sudden or significant changes in the levels of organisms can indicate problems with the water supply.

How can an exceedance of Colony Count occur? 
An exceedance of this parameter indicates an inadequate disinfection system . It may also indicate that there is not enough residual chlorine to deal with the amount of bacteria in the water.  

How is an exceedance of Colony Count dealt with? 
All Exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Cryptosporidium?
Cryptosporidium is a tiny parasite found in human and animal waste. If ingested, it can cause a disease called Cryptosporidiosis which has symptoms such as fever, stomach upset, weight loss and diarrhoea. These micro-organisms can survive in the environment for several months. Not all species or types of Cryptosporidium are harmful to humans; the main species that can cause illness are Cryptosporidium parvum and Cryptosporidium hominis. In the Drinking Water Regulations it is defined as a Microbiological parameter.

What is a Cryptosporidium exceedance?
A drinking water exceedance is a result from a drinking water sample which is above the acceptable limit. The Cryptosporidium test typically involves pumping approx. 1,000 litres of drinking water through a special filter to check for and trap any Cryptosporidium. Any detection of Cryptosporidium in a drinking water sample is regarded as an exceedance.

What can cause a Cryptosporidium exceedance?
Exceedances for Cryptosporidium can occur following a contamination incident or a failure in the treatment process to remove or inactivate it.

How are Cryptosporidium exceedances dealt with?
Uisce Éireann reports all detections of Cryptosporidium in drinking water to the HSE and the EPA. All information regarding a Cryptosporidium exceedance is provided to the HSE, who are the experts in public health and a decision is made following a consultation if a Boil Water Notice is required. The HSE also provides regular updates to both Uisce Éireann and Local Authorities on any reported incidences of Cryptosporidiosis. All Cryptosporidium exceedances are fully investigated to determine the cause, with suitable corrective actions (e.g. UV treatment) being identified and implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is E. coli?
The full name for E. coli is Escherichia coli. It is a type of bacteria found in in the intestines of humans and animals. In the drinking water regulations it is defined as a Microbiological parameter. Certain strains (i.e. types) of E. coli (e.g. O157:H7) can cause serious illness such as gastroenteritis, dysentery, and diarrhoea.

What is an exceedance for E. coli?
The acceptable limit for E. coli in drinking water is 0 per 100mls. Therefore any detection of E. coli in a drinking water sample is seen as an exceedance.

What can cause an E. coli exceedance?
Exceedances for E. coli can be due to a contamination incident either at a water source or through the water network, for example at burst mains or at an illegal connection etc. Exceedances of E. coli can also occur due to a failure in the disinfection treatment process.

How are exceedances for E. coli dealt with?
Uisce Éireann reports all exceedances for E. coli to the HSE and EPA. All information regarding an E. coli exceedance is provided to the HSE, who are the experts in public health and a decision is made following consultation if a Boil Water Notice is required. All exceedances for E. coli are fully investigated to determine the cause and to ensure that suitable corrective actions are taken to ensure the water supply is adequately disinfected.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What are Enterococci?
Enterococci are bacteria found in the intestines of humans and animals. Certain strains of enterococci (e.g. Enterococcus Faecalis) can cause illness in humans . People with weakened immune systems are particularly susceptible to infection from Enterococci. In the Drinking Water Regulations it is defined as a Microbiological parameter.

What is an exceedance for Enterococci?
The acceptable limit for Enterococci in drinking water is 0 per 100mls. Therefore any detection of Enterococci in a drinking water sample is seen as an exceedance.

What can cause an Enterococci exceedance?
Exceedances for Enterococci can be due to a contamination incident either at source or through the water network, for example at a burst mains or at an illegal connection etc. Exceedances of Enterococci can also be due to a failure in the disinfection treatment process.

How are exceedances for Enterococci dealt with?
Uisce Éireann reports all exceedances for Enterococci to the HSE and EPA. All information regarding an Enterococci exceedance is provided to the HSE, who are the experts in public health and a decision is made following consultation if a Boil Water Notice is required. All exceedances for Enterococci are fully investigated to determine the cause and to ensure that suitable corrective actions are taken to ensure the water supply is adequately disinfected.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Giardia?
Giardia is a tiny parasite found in the environment and, if ingested, can cause a disease called Giardiasis. The symptoms of this infection include abdominal cramps, nausea, diarrhoea and bloating. The organism is protected by an outer shell, called a cyst, which protects it and allows it to survive for long periods outside a host. Drinking water should be free from Giardia. In the Drinking Water Regulations it is defined as a Microbiological parameter.

What is an exceedance for Giardia?
There is no limit designated for this parameter in the EU drinking water directive, however,  water intended for consumption should be free of any micro-organisms and parasites and from any substances which, in numbers or concentrations, constitute a potential danger to public health.

What can cause a Giardia exceedance?
Exceedances for Giardia can occur following a contamination incident or a failure in the treatment process to remove or inactivate it.

How are Giardia exceedances dealt with?
Uisce Éireann reports all detections of Giardia in drinking water to the HSE and the EPA. All information regarding a Giardia exceedance is provided to the HSE, who are the experts in public health and a decision is made following a consultation if a Boil Water Notice is required. All Giardia exceedances are fully investigated to determine the cause, with suitable corrective actions (e.g. UV treatment) being identified and implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What are Total Coliforms?
Coliforms are naturally occurring organisms in soil, water and vegetation. Coliform Bacteria should not be present in water that is disinfected and their presence indicates that either disinfection has not been complete, that there is ingress into the water mains in the distribution network or that the sampling point is contaminated. In the Drinking Water Regulations it is defined as an Indicator parameter.

What is a Total Coliforms Exceedance?
A drinking water exceedance is a result from a drinking water sample which is above the acceptable limit. Any detection of Total Coliforms in a drinking water sample is seen as an exceedance.

What causes a Total Coliforms Exceedance?
Exceedances for Total Coliforms can occur following a localised contamination incident or where water is not adequately chlorinated in the disinfection treatment process.

How are Total Coliforms exceedance dealt with?
All exceedances for Total Coliforms are assessed by Uisce Éireann and notified to the HSE where necessary to seek their advice in relation to the protection of public health. Total Coliform exceedances are also notified to the EPA where there is a risk to public health, or where the exceedance indicates a persistent issue. All Total Coliform exceedances are investigated to determine the cause, with corrective actions (e.g. checking of chlorination levels and flushing of mains) being identified and implemented where required.  

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is 1,2-Dichloroethane? 
This is a chemically manufactured liquid, most commonly employed in the production of vinyl chloride that is used to manufacture a variety of plastic and vinyl products i.e. PVC pipes, construction and packaging materials. 1,2-dichloroethane is present in some industrial effluent and has occasionally been found in drinking water supplies elsewhere. In the Drinking Water Regulations it is defined as a Chemical parameter.

What is an exceedance for 1,2-Dichloroethane?
The limit set out in the drinking water directive for 1,2-Dichloroethane is 3.0μg/l. Therefore any result above this level is an exceedance for 1,2-Dichloroethane.

How would an exceedance for 1,2-Dichloroethane occur?
The presence of 1,2-dichloroethane exceedances in drinking water typically indicates the occurrence of a pollution event.

How are exceedances of 1,2-Dichloroethane dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Acrylamide? 
Acrylamide is a chemical compound (C3H5NO). In the Drinking Water Regulations it is defined as a Chemical parameter. When Acrylamide molecules bind together they form a chain called polyacrylamide, a synthetic substance that is used in water-based applications including water treatment and sludge treatment.

What is an exceedance for Acrylamide?
Under the Drinking Water Regulations, the maximum parametric limit is 0.10μg/litre. Therefore any result above this level is an exceedance for Acrylamide.

What is the cause of an Acrylamide exceedance? 
Acrylamide in drinking water most likely indicates the use of polyacrylamide in the treatment process. It may also, although rarely, arise from the use of polyacrylamides as grouting agents in water storage tanks, wells or reservoirs.

How are exceedances of Acrylamide dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and implement suitable corrective action.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Ammonium (NH4)?

Ammonium (NH4) is a colourless and potent gas that is widely used to make nitrogen based fertilisers. It is oxidised in the environment and may also be present in trace amounts in natural waters at concentrations less than 0.1 mg/litre. When concentrations are found to be significantly greater than 0.1 mg/litre, i.e. tens to hundreds of mg/litre, it indicates large scale contamination. Ammonia in water can cause corrosion of copper pipes and fittings, causing stains cloths and towels etc. In the Drinking Water Regulations it is defined as an Indicator parameter.

What is an exceedance of Ammonium (NH4)?

The limit designated for Ammonium (NH4)) in the EU drinking water directive is 0.50mg/l. Therefore any result above this level is an exceedance for Ammonium.

How can an exceedance of Ammonium (NH4) occur?

The presence of Ammonium (NH4) in water supplies indicates contamination from agricultural or industrial practices as well as sewage systems. Increased levels of ammonium can also occur in areas heavily used for agriculture.

How is an exceedance of Ammonium (NH4) dealt with?

All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Benzene?
Benzene is an organic solvent used in the manufacturing industry and is present in petrol, diesel, and kerosene. As it does not occur naturally in water, the main causes of Benzene in water are air pollution, chemical plant effluent and leakage from petrol tanks. In the Drinking Water regulations it is defined as a Chemical parameter.

What is an exceedance for Benzene? 
The limit for Benzene set out in the drinking water directive is 1.0μg/l. Therefore any result above this level is an exceedance for Benzene.

How can an exceedance of Benzene occur? 
Emissions from motor vehicles account for most of the Benzene in the air, which can in due course reach water sources as well as industrial pollution.

How are exceedances for Benzene dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Benzo(a)pyrene? 
Benzo(a)pyrene is a substance of public health concern because of its carcinogenic (cancer causing) properties. It is an environmental pollutant, and is also found in tobacco smoke. This is a naturally occurring chemical compound [C20H12] and also found in coal, tar and oil. It is one of several polycyclic aromatic hydrocarbons [PAHs] and is derived from benzene. The undesirability of the presence of, and the need to restrict the concentrations of, Benzo(a)pyrene is indicated clearly by its designation as a discrete parameter in Drinking Water Directive [98/83/EC].  In the Drinking Water Regulations it is defined as a Chemical parameter.

What is an exceedance of Benzo(a)pyrene?
The limit for Benzo(a)pyrene set out in the drinking water directive is 0.010µg/l. Therefore any result above this level is an exceedance for Benzo(a)pyrene.

How would an exceedance for Benzo(a)pyrene occur? 
A Benzo(a)pyrene exceedance in drinking water indicates that during the treatment process, a contaminated product has been used, however, it is more than likely due to chemical pollution.

How are exceedances for Benzo(a)pyrene dealt with? 
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Bromate?
Bromate can be detected in drinking water either as a by-product of disinfection or due to a pollution event. The amount of Bromate formed depends on the amount of naturally-occurring bromide in the water. In the Drinking Water Regulations it is defined as a Chemical parameter.

What is an exceedance of Bromate?
The limit for Bromate set out in the drinking water directive is 10μg/l. Therefore any result above this level is an exceedance for Bromate.

How would an exceedance for Bromate occur?
Bromate exceedances in drinking water can be associated with the use of ozone as a disinfectant. It can on occasion be due to higher levels of Bromate (than normal) in batches of Sodium Hypochlorite used to disinfect the water. Uisce Éireann regularly engages with our suppliers to ensure the chemicals used at our treatment plants conform to the required standard.

How are the exceedances for Bromate dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Chloride? 
Chloride is a naturally occurring mineral in drinking water and comes from mineral salts in the environment. The most common are hardness salts e.g. calcium. Chloride is a component of Sodium Chloride [NaCl] or table salt and is part of a normal diet. Sodium Chloride is also used to manufacture industrial chemicals i.e. Chlorine, Caustic Soda, Sodium Chlorite and Hypochlorite. It is also a component of Potassium Chloride which is commonly used as a fertilizer, in medicine, scientific applications and food processing. In the Drinking Water Regulations it is defined as a Chemical parameter.

What is an exceedance of Chloride?
The limit designated to Chloride in the EU drinking water directive is 250mg/l. Therefore any result above this level is an exceedance for Chloride.

How can an exceedance of Chloride occur?
The presence of excessive chloride in water supplies more than 30 kms from the coast is an indicator of pollution. Because sewage is such a rich source of chloride, a high result may indicate pollution of water by a sewage effluent. Natural levels in rivers and other fresh waters are usually in the range 15-35 mg/l Cl - much below drinking water standards.

How is a Chloride exceedance dealt with?  
All Exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Cyanide?
Cyanide is a colourless gas not normally present in drinking water. The most commonly-used form, hydrogen Cyanide, is mainly used to make compounds needed to manufacture synthetic fibres such as nylon. Other forms of Cyanide are used as herbicides or in the mining industry. It is highly toxic and can cause death to humans and animals. In the drinking water regulations it is defined as a Chemical parameter.

What is an exceedance for Cyanide?
The limit set out in the drinking water directive for Cyanide is 50μg/l. Therefore any result above this level is an exceedance for Cyanide.

How would a Cyanide exceedance occur?
A Cyanide exceedance in drinking water may be as a result of an industrial spill or incident, with the source water for the treatment plant becoming contaminated.

How are exceedances for Cyanide dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented. A Cyanide exceedance may be as a result of an industrial spill or incident, with the source water for the treatment plant becoming contaminated. Therefore initial investigations following a Cyanide exceedance would focus on this area.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Epichlorohydrin? 
Epichlorohydrin is a flammable liquid used in the production of plastics, epoxy resins, phenoxy resins and other polymers, some of which are used in the water treatment process or to coat pipes and other water retainers. In the Drinking Water Regulations it is defined as a Chemical parameter.

What is an exceedance of Epichlorohydrin?
The limit set out in the drinking water directive for Epichlorohydrin is 0.10μg/l. Therefore any result above this level is an exceedance for Epichlorohydrin.

How would an exceedance for Epichlorohydrin occur?
The presence of Epichlorohydrin exceedances in drinking water indicates issues in the water treatment process. 

How are exceedances of Epichlorohydrin dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented. Epichlorohydrin concentrations in drinking water are controlled by limiting either the content of the substance in polyamine flocculants or the dose used.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Fluoride?
Fluoride can occur naturally in some water sources however it is mostly found in drinking water due to Fluoride being added as part of the treatment process. Public water supplies in Ireland and in many other countries add fluoride, typically in the form of Hydrofluorosilicic acid (H2SiF6), to drinking water to reduce cavities in teeth. In the Drinking Water Regulations it is defined as a Chemical parameter.

What is an exceedance for Fluoride?The limit designated for Fluoride in the EU drinking water directive is 1.5mg/l. Therefore any result above this level is an exceedance for Fluoride.

How would an exceedance for Fluoride occur?
Fluoride exceedances in supplies where Fluoride is not added indicates that the source has naturally-occurring high levels. However if an exceedance occurs in a supply where Fluoride is added to the water then it suggests that an issue has occurred with the dosing system at the treatment plant.

How are exceedances for Fluoride dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Nitrate (NO3)?
Nitrate (NO3) is found naturally in the environment and is an important plant nutrient. It is present at varying concentrations in all plants and is part of the nitrogen cycle. Naturally occurring soil nitrates are essential for plant growth. Nitrates will also occur naturally in compost and in wastewater treatment systems. Natural levels of nitrates in soil are increased by the use of nitrogen-based inorganic fertilisers, a portion of which aren't taken up by plants and may instead leach into groundwater supplies over time. In the Drinking Water Regulations it is defined as a Chemical parameter.

What is an exceedance for Nitrate (NO3)
The limit for Nitrate (NO3) set out in the drinking water directive is 50mg/l. Therefore any result above this level is an exceedance for Nitrate (NO3).

How would an exceedance for Nitrate (NO3) occur?
The presence of nitrates (especially where a consistent high concentrations are detected) tells us that the supply source water is being polluted.

How are exceedances for Nitrate (NO3) dealt with?
All exceedances for nitrate are notified to the HSE and Uisce Éireann consults with them to seek their advice in relation to the protection of public health. Nitrate exceedances are also notified to the EPA where there may be a risk to public health, or where the exceedance indicates a persistent issue. Nitrate exceedances are fully investigated to determine the cause and suitable corrective actions (e.g. putting an exclusion zone around a water source, re-drilling a water source at a different location or installing a nitrate removal system) are identified and implemented where required.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Nitrite (NO2)?
Nitrite (NO2) is a nutrient and an intermediate compound in the conversion of ammonia to nitrate in the nitrogen cycle. Nitrite can also be formed chemically in distribution pipes by Nitrosomonas bacteria during stagnation of nitrate containing and oxygen-poor drinking water in galvanized steel pipes or if chlorination is used to provide a residual disinfectant. In the Drinking Water Regulations it is defined as a Chemical parameter.

What is an exceedance for Nitrite (NO2)?
The limit set out in the drinking water directive for Nitrite is 0.5mg/l. Therefore any result above this level is an exceedance for Nitrite (NO2).

How would an exceedance of Nitrite (NO2) occur? 
The presence of elevated Nitrite (NO2) concentrations indicates a pollution event has occurred at source.

How are Nitrite (NO2) exceedances dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What are Pesticides?  
Pesticides are chemicals used to control the growth of unwanted weeds, plants, insects, algae, etc. Pesticides can enter water courses as a result of agricultural and non-agricultural use. The Drinking Water Regulations define Pesticides as including organic insecticides, herbicides, fungicides, nematocides, acaricides, algicides, rodenticides, slimicides, including their relevant metabolites, degradation and reaction products. In Ireland the most commonly found individual pesticide in drinking water supplies is the acid herbicide MCPA. This pesticide is used primarily to control the growth of rushes in poorly drained land. In the Drinking Water Regulations Pesticides are defined as Chemical parameters.

What is an exceedance for an Individual Pesticide?
The parametric value for all individual pesticides is 0.10µg/l, except for Aldrin, Dieldrin, Heptachlor & Heptachlor Epoxide where the parametric value is 0.030µg/l. Therefore any result above these specified levels for these individual pesticides is an exceedance.

How would an exceedance of the Pesticides parameter occur?
The presence of an individual pesticide at levels exceeding the maximum value tells us that there may have been careless or excessive use of a product in the catchment area upstream of where water is abstracted for treatment.

How are exceedances of Individual Pesticides dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented. In the case of Individual Pesticide exceedances Uisce Éireann engages with the relevant statutory authorities with responsibility for protecting the catchment (e.g. Local Authority Environment Sections, EPA catchment units). We also engage with non statutory bodies such as the Pesticides Control Division in the Dept. of Agriculture, Teagasc, Coillte etc. Education and awareness of responsible Pesticide use in the catchment is one of the primary means of preventing Pesticides from ending up in drinking water.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency
University of Hertfordshire Pesticide Properties Database

What Are Total Pesticides? 
This is the total concentration of all individual pesticides tested in a drinking water sample - see Individual Pesticides above. In the Drinking Water Regulations Total Pesticides are defined as a Chemical parameter.

What is an exceedance for the Total Pesticides parameter?
The limit for the Total Pesticides parameter set out in the drinking water regulations is 0.50μg/l. Therefore any result above this level is an exceedance for the Total Pesticides parameter.

How would an exceedance of the Total Pesticides parameter occur?
Breaches of the Total Pesticide limit are due to one of more of the Individual Pesticides also tested in the sample being detected at levels exceeding the maximum value. This would indicate that there may have been careless or excessive use of a product in the catchment area upstream of where water is abstracted for treatment.

How are Total Pesticides exceedances dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented. In the case of Individual Pesticide exceedances Uisce Éireann engages with the relevant statutory authorities with responsibility for protecting the catchment (e.g. Local Authority Environment Sections, EPA catchment units) but also non statutory bodies such as the Pesticides Control Division in the Dept. of Agriculture, Teagasc, Coillte etc.) Education and awareness of responsible Pesticide use in the catchment is one of the primary means of preventing Pesticides from ending up in drinking water.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency
University of Hertfordshire Pesticide Properties Database

What are Polycyclic Aromatic Hydrocarbons (PAH)?
Polycyclic Aromatic Hydrocarbons are chemical compounds found in soot, tar, car exhausts and combustion products of petroleum based fuels. In the Drinking Water Regulations there are 4 specified parameters that are combined to give a total PAH result - these are: benzo(b)fluoranthene; benzo(k)fluoranthene; benzo(ghi)perylene; indeno(1,2,3-cd)pyrene. PAHs are defined as Chemical parameters in the Drinking Water Regulations.

What is an exceedance for PAH?
The limit set out in the drinking water directive is 0.10μg/l. Therefore any result above this level is an exceedance for Polycyclic Aromatic Hydrocarbons (PAH).

How would an exceedance for PAH occur?
PAH exceedances in drinking water indicate that a petroleum spillage or incident has occurred in the catchment or in the distribution network. PAHs have the ability to pass through sealed PVC pipework and therefore the mains distribution system is particularly at risk following a fuel spill.

How are exceedances for Polycyclic Aromatic Hydrocarbons (PAH) dealt with?  
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented. Depending on the severity of the incident giving rise to the PAH exceedance the response may require an extensive clean up or even mains pipe replacement.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Sulphate?
Sulphates occur naturally in the environment in a number of minerals. It is used in the manufacture of many products including dyes, paper and textiles. Iron sulphides are present in sedimentary rocks from which they can be oxidised to sulphate in humid climates; the latter may then leach into watercourses so that ground waters are often excessively high in sulphates. Excessive amounts of sulphate will result in a taste issue while sources with depleted dissolved oxygen sulphate will emit an unpleasant smell and can also increase corrosion in pipes. In the Drinking Water Regulations it is defined as a Indicator parameter.

What is an exceedance for Sulphate?  
The Sulphate limit designated in the EU drinking water directive is 250mg/l. Therefore any result above this level is an exceedance for Sulphate.

How can a Sulphate exceedance occur? 
Sulphates are in nearly all natural waters, but the concentration will be affected by local geological factors or by discharges from industrial processes.

How are Sulphate exceedances dealt with?
All Exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What are Tetrachloroethene and Trichloroethene?
Tetrachloroethene and Trichloroethene are industrial solvents which are rarely found in drinking water. They are colourless, toxic liquids used as industrial solvents and in dry-cleaning solutions. In the Drinking Water Regulations these two chemicals are reported as a single combined parameter (i.e. the sum of both compounds). Tetrachloroethene and Trichloroethene are defined in the Drinking Water Regulations as a Chemical parameter.
 
What is an exceedance for Tetrachloroethene and Trichloroethene?
The limit designated in the EU drinking water directive is 10μg/l. Therefore any result above this level is an exceedance for Tetrachloroethene and Trichloroethene.
 
How would an exceedance for Tetrachloroethene and Trichloroethene occur?
An exceedance for Tetrachloroethene and Trichloroethene in drinking water indicates that the water source for the supply has been contaminated, most likely due to a pollution incident.
 
How is an exceedance of Tetrachloroethene and Trichloroethene dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented. Tetrachloroethene and Trichloroethene levels can be reduced in drinking water using advanced treatment technologies such as granular activated carbon. This however would only be considered if the issue was persistent and an alternative water supply was not available.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What are trihalomethanes?
The addition of chlorine is an essential step to ensure harmful bacteria are eliminated from your drinking water. A consequence of this process however is the formation of Trihalomethanes (THMs for short), which occurs when the chlorine that is used for disinfection purposes reacts with organic matter in the water. This reaction primarily depends on the purity of the treated water (i.e. the amount of organic matter present), the amount of chlorine added, and the length of time before the drinking water reaches your tap.

What is a THM exceedance?
A drinking water exceedance is a result from a drinking water sample which is above the acceptable limit. The limit for THMs in drinking water is 100µg/l, therefore any result greater than this is seen as a THM exceedance.

What causes a THM exceedance?
Exceedances for THMs can occur in large networks, where the chlorine in the water has a longer period of time to react with any organic matter that may be present. This process can occur faster during warmer weather and/or where higher chlorine levels are present in the water.
 
How are THM exceedances dealt with?
Uisce Éireann reports all exceedances of THMs to the HSE and EPA. All relevant information regarding THM exceedances is provided to the HSE and their advice is requested in relation to protecting public health. All exceedances for THMs are fully investigated to determine the cause and to ensure that suitable corrective actions are taken.
 
What is Uisce Éireann doing about THMs?
Uisce Éireann is taking action to remove the risk of elevated levels of THMs forming in all public water supplies. We have initiated a prioritised programme of investment to address all treatment deficiencies, including those for THMs. With this programme we are committed to improving water quality through investment in water services infrastructure and are targeting specific Water Supply Zones where the risk of elevated THMs are highest. We are also upgrading and optimising the treatment processes at all water treatment plants across the country. This includes controlling the concentration of chlorine in the water, one of the key measures in controlling THM formation, as well as the reorganisation of networks and regular flushing of storage reservoirs and pipelines.

For further information on this drinking water parameter and others please visit the following websites:

Uisce Éireann
World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Vinyl Chloride?
Vinyl Chloride is a Synthetic gas and is an important raw material in the manufacture of plastics. It is also used as a refrigerant. The main cause of vinyl chloride in drinking water is usually leaching from uPVC piping and discharge from plastics factories. In the Drinking Water Regulations it is defined as a Chemical parameter.

What is an exceedance of Vinyl Chloride?
The limit designated for Vinyl Chloride in the EU drinking water directive is 0.50μg/l. Therefore any result above this level is an exceedance for Vinyl Chloride.
 
How can an exceedance of Vinyl Chloride occur?
The presence of Vinyl Chloride in water suggests that an industrial effluent has caused pollution at source.
 
How is an exceedance for Vinyl Chloride dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.    

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Aluminium?
Aluminium is found as a natural substance in water but can also be used in the treatment process in the form of Aluminium sulphate. This chemical however is removed during the water treatment process. Outside of the treatment process it is used in the construction, motor and aircraft industries as well as in cookware, soft-drink cans and tin foil. It is an indicator parameter for drinking water which means that it may indicate the presence of other parameters in a water sample. Aluminium occurs naturally in small amounts in both surface and ground waters (e.g. rivers or natural wells). In the Drinking Water Regulations it is defined as a Indicator parameter.
 
What is an Aluminium exceedance?
A drinking water exceedance is a result from a drinking water sample which is above the acceptable limit. The limit for aluminium in drinking water is 200µg/l, therefore any result that is greater than this is seen as an aluminium exceedance.
 
What can cause an Aluminium exceedance?
Aluminium can be used in surface water treatment plants (usually in the form of aluminium sulphate) to remove impurities from raw water. Exceedances for aluminium can occur where small quantities of aluminium remain in the water following the treatment process.
 
How are exceedances for Aluminium dealt with?
All exceedances for aluminium are notified to the HSE and Uisce Éireann consults with them to seek their advice in relation to the protection of public health. Aluminium exceedances are also notified to the EPA where there may be a risk to public health, or where the exceedance indicates a persistent issue. Aluminium exceedances are fully investigated to determine the cause and suitable corrective actions are taken.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Antimony? 
Antimony is a naturally occurring trace element, resembling a metal in its appearance and physical properties, its most common form is a hard, extremely brittle, lustrous, silver white, crystalline material. In the drinking water regulations it is defined as a Chemical parameter. It is used as a compound in a wide variety of alloys, especially with lead in battery plates and in the manufacture of flame-proofing compounds, paint, semiconductor devices and ceramic products.

What is an exceedance for Antimony?The limit for Antimony set out in the EU drinking water directive is 10.0μg/l. Therefore any result above this level is an exceedance for Antimony.

What is the cause of an Antimony exceedance? 
Antimony can occur naturally in very low levels from the erosion of rocks. The largest emissions are associated with copper and lead mining, solvent recovery, and metal industries. Trace levels in drinking water have been associated with internal plumbing issues.

How are exceedances of Antimony dealt with? 
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Arsenic?
Arsenic can typically be found in certain groundwater sources due to influence from minerals and rocks. Is has also been linked to industrial pollution incidents. In the Drinking Water Regulations it is defined as a Chemical parameter.
 
What is an exceedance for Arsenic? 
The limit for Arsenic set out in the EU drinking water directive is 10μg/l. Therefore any result above this level is an exceedance for Arsenic.
 
What is the cause of an Arsenic exceedance?
Arsenic exceedances in drinking water indicates naturally high concentrations at the source or a possible chemical pollution incident.
 
How are exceedances for Arsenic dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Boron? 
It is a naturally-occurring mineral that is found in food and the environment. It is used in the chemical, medical, cosmetic and agricultural industries. In the drinking water regulations it is defined as a Chemical parameter. Metallic Boron is extremely hard and has a very high melting point. Boron compounds are usually found in sediments and sedimentary rock formations and have a wide range of uses from glass-making and ceramics to cosmetic products, antiseptics, food preservatives, agricultural fertilisers, algicides, herbicides and insecticides.

What is an exceedance of Boron? The limit for Boron set out in the EU drinking water directive is 1.5 mg/l. Therefore any result above this level is an exceedance for Boron.

How would an exceedance for Boron occur? 
Boron exceedances in drinking water tell us either that natural leaching of Boron containing minerals has occurred, or that there has been a contamination incident. The main threat of Boron contamination comes from industrial discharges or from detergents in sewage effluent.

How are the exceedances for Boron dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Cadmium? 
Cadmium is a chemical that can naturally occur in rocks but its presence in drinking water is mostly due to industrial waste and/or accidental drainage from landfills to the environment. In the drinking water regulations it is defined as a Chemical parameter. Cadmium metal is used in the steel industry and in plastics and Cadmium compounds are widely used in batteries. Contamination in drinking-water may also be caused by impurities in the zinc of galvanized pipes and solders and some metal fittings. Cadmium concentrations in most water sources are usually lower than 1.0μg/litre.

What is an exceedance for Cadmium?
The limit for Cadmium set out in the EU drinking water directive is 5μg/l. Therefore any result above this level is an exceedance for Cadmium.

How would an exceedance for Cadmium occur?
The presence of cadmium exceedances in drinking water tells us either that source levels are high or that there is a pollutant entering the supply.

How are exceedances for Cadmium dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Chromium? 
Chromium is a chemical that occurs naturally in rock but is often found in surface waters due to industrial waste discharges. The latter is considered more hazardous but because it is difficult to distinguish by analysis, therefore total chromium concentrations are reported.  In the Drinking Water Regulations it is defined as a Chemical parameter. Its presence in water would indicate industrial and domestic chromium waste discharges or from contaminated land.

What is an exceedance for Chromium?
The limit set out in the drinking water directive for Chromium is 50μg/l. Therefore any result above this level is an exceedance for Chromium.

What can cause a Chromium exceedance?  
The presence of Chromium exceedances in drinking water suggests that there has been a pollution occurrence at the abstraction source.

How are exceedances for Chromium dealt with? 
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Copper?
Copper is an essential nutrient in the diet but it can be toxic at high concentrations. It is used to make pipes, valves and fittings and is present in alloys. It occurs naturally in rocks, soils, water, sediment, air, plants and animals. In the drinking water regulations it is defined as a Chemical parameter.

What is an exceedance for Copper?
The limit set out in the drinking water directive for Copper is 2mg/l. Therefore any result above this level is an exceedance for Copper.

How would a Copper exceedance occur?
The main cause of a Copper exceedance is typically due to drinking water coming in contact with internal (i.e. private side) Copper plumbing and fittings containing Copper. All water is corrosive towards Copper to some degree, causing it to dissolve into the drinking water. Low pH (acidic) or high pH (alkaline) water can cause a higher concentrations of Copper to dissolve from pipework.

How are exceedances for Copper dealt with?  
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented. In respect of Copper, studies by Uisce Éireann have shown that flushing the tap for at least 1 minute is an effective means of reducing Copper levels in drinking water to below the 2mg/L limit. Controlling the pH of the water leaving the treatment plant may also reduce the likelihood of Copper dissolving from plumbing or fittings. In the first instance however it is recommended that the homeowner should engage a competent plumber to examine their internal plumbing arrangement to ensure any drinking water pipework is not constructed from Copper.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Iron? 
Iron occurs naturally in the environment Iron and has many domestic and industrial uses including supplements to prevent deficiency, in food colouring, iron and steel products as well as in the water treatment process in the form of Ferric Sulphate. Some older watermains are made from cast iron and may corrode to give the water a rust coloured appearance which may not necessarily pose a health risk, but would not be acceptable in terms of taste or appearance. In the Drinking Water Regulations it is defined as an Indicator parameter.

What is an Iron exceedance?
A drinking water exceedance is a result from a drinking water sample which is above the acceptable limit. The limit for Iron in drinking water is 200µg/l, therefore any result that is greater than this is seen as an iron exceedance.

What causes an Iron exceedance? 
The main cause of Iron exceedances in drinking water is due to disruption of Iron sediment in old cast Iron mains. Iron exceedances can also occur when small amounts of Iron-based coagulants (e.g. Ferric Chloride or Ferric Sulphate) that are used in some water treatment processes, are carried over from the treatment stages and can be found in drinking water.

How are Iron exceedances dealt with? 
All exceedances for iron are notified to the HSE and Uisce Éireann consults with them to seek their advice in relation to the protection of public health. Iron exceedances are also notified to the EPA where there may be a risk to public health, or where the exceedance indicates a persistent issue. Iron exceedances are fully investigated to determine the cause, with suitable corrective actions being identified and implemented. Uisce Éireann is working to reduce iron exceedances through regular mains flushing and control of coagulant dosing processes (where iron-based coagulants are used in water treatment processes).   

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Lead? 
Lead is a metal that is found in soil, rocks, air and water. In the past, it was widely used to make water pipes until it was discovered to be associated with significant health problems. Many older houses (i.e. 1970s and older) may still have lead pipes or fittings containing lead and it is likely in these cases that the drinking water may be above safe levels.  In the Drinking Water Regulations it is defined as a Chemical parameter.
 
What is a Lead exceedance?
A drinking water exceedance is a result from a drinking water sample which is above the acceptable limit. The limit for lead in drinking water is 10µg/l, therefore any result greater than this is seen as a lead exceedance.
 
What causes a Lead exceedance?
The main cause of lead in drinking water is due to lead 'leaching' from lead pipes and plumbing fittings into the water.
 
How are Lead exceedances dealt with?
Uisce Éireann reports all detections of lead in drinking water to the HSE and EPA. Exceedances for lead are usually site specific, i.e. a lead exceedance detected at one location within a water supply does not mean that the entire water supply will be affected. The is an agreed process in place with the EPA and HSE whereby properties that have been identified as having a lead exceedance will be written to and provided with important information as to the relevant steps they can take.

For further information on this drinking water parameter and others please visit the following websites:

Uisce Éireann - Lead in Drinking Water
World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Manganese?
Manganese occurs naturally in the environment and is also found in many foods in the diet (e.g. vegetables, tea). It also occurs naturally in some water sources and is removed during water treatment process. Manganese is an essential element and is required by mammals and birds for normal growth. Most divalent compounds are soluble in water, as is heptavalent permanganate. The most common tetravalent compound, Manganese Dioxide, is insoluble. Manganese is principally used in the manufacture of iron, steel and alloys. In the Drinking Water Regulations it is defined as an Indicator parameter.

What is an exceedance for Manganese?
The limit designated in the EU drinking water directive for Manganese is 50µg/l. Therefore any result above this level is an exceedance for manganese.

How can an exceedance for Manganese occur?
Manganese exceedances in a drinking water supply may point to pollution of the source water although some exceedances arise from naturally-occurring high levels at source.

How is an exceedance for Manganese dealt with? 
All Exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive FAQ for Manganese in Drinking Water
Environmental Protection Agency

What is Mercury?
Mercury is a toxic metal which is generally industrial in origin. It is used in the manufacture of anti-fouling paints, plastics and paper-making. It is poisonous at high levels. The potential sources of mercury in drinking water are erosion of natural deposits, discharge from refineries and factories, run-off from landfills. In the Drinking Water Regulations it is defined as a Chemical parameter.

What is an exceedance for Mercury?
The limit for Mercury set out in the drinking water directive is 1.0μg/l. Therefore any result above this level is an exceedance for Mercury.

How would a Mercury exceedance occur?
The presence of inorganic Mercury in drinking water indicates pollution of the source.

How are exceedances for Mercury dealt with?  
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Nickel? 
Nickel can be found in trace amounts in most water supplies depending on the location and rock type. It is used in the manufacture of coins, iron, brass, alloys and in the production of stainless steel. Nickel can be found on the coatings on some taps and plumbing fittings and this is typically the main source of Nickel in drinking water. However, raw water can be contaminated by diffuse nickel emissions from power plants, waste incinerators and metal industries, while discharge to surface waters from various industries can also be problematic. In the Drinking Water Regulations it is defined as a Chemical parameter.

What is an exceedance for Nickel? 
The limit for Nickel set out in the drinking water directive is 20μg/l. Therefore any result above this level is an exceedance for Nickel.

How would an exceedance for Nickel occur? 
Nickel exceedances in drinking water typically where water in a property is in contact with plumbing material that contain Nickel or is Nickel-plated.

How are exceedances for Nickel dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented. In the case of Nickel, studies undertaken by Uisce Éireann have shown that in properties where exceedances have been detected, flushing the tap for at least one minute is an effective measure of reducing Nickel concentrations to a safe level.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Selenium?
Selenium is a metal found in natural deposits such as rocks. Selenium is essential in the diet however it is toxic at high levels. It is widely used in Industry, e.g. in the areas of electronics and photography. Selenium is released from natural and human-made sources, with the main source being the burning of coal. The major use of Selenium is in the manufacture of electronic components and in photography. Selenium compounds are used in some insecticides. In the drinking water regulations it is defined as a Chemical parameter.

What is an exceedance of Selenium?The limit set out in the drinking water directive for Selenium is 20μg/l. Therefore any result above this level is an exceedance for Selenium.

How would an exceedance for Selenium occur?
An exceedance for Selenium in drinking water typically indicates that the water source is contaminated, either from natural sources (rock etc.) or from an industrial spillage.

How is an exceedance for Selenium dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented. Selenium concentrations can be lowered by the coagulation process which is a form of chemical treatment in conventional water treatment plants. 

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Sodium? 
Sodium is an element that is naturally present in seawater and groundwater and therefore naturally occurs in nearly all water supplies. It is an essential component of the diet and is most commonly found in table salt. Sodium salts are used in the pharmaceutical and chemical industries. Sodium levels in the majority of public water supplies are typically less than 200mg/litre but levels greater then 200 mg/litre have been detected and these occurrences were typically due to sea water influence on the source. In the Drinking Water Regulations it is defined as an Indicator parameter.

What is an exceedance of Sodium?
The designated limit for Sodium in the EU drinking water directive is 200mg/l. Therefore any result above this level is an exceedance for Sodium.

How can a Sodium exceedance occur? 
Where source values are normally low, excessive sodium might indicate pollution of the source by wastewater treatment systems. Other water sources on occasion have been impacted by Sodium where runoff from roads treated with salt has occurred.

How are Sodium exceedances dealt with?
All Exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Colour? 
Colour in drinking water is caused by the interaction of light with suspended and dissolved particles. As these particles are likely to have colour of their own, the colour will appear higher if the amount of particles are above an acceptable standard. Water that is treated should be clear, bright and free from colour with no abnormal change in its appearance. In the Drinking Water Regulations it is defined as an Indicator Parameter.

What is an exceedance of the Colour parameter?
There is no designated limit for Colour in the EU drinking water directive, however, drinking water must be acceptable to consumers and no abnormal change in colour should occur.   

How can an exceedance of Colour occur?
The presence of Colour in surface water is mostly due to the presence of dissolved organic matter from soil and decaying vegetable matter. Groundwater Colour can occur due to the presence of iron. In drinking water, change in Colour may indicate degradation of the water source, corrosion in the distribution system, or changes during the treatment processes.

How are Colour exceedances dealt with?
All Exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Conductivity? 
Conductivity is the measure of the water's ability to conduct an electrical current. It is conducted through water by the dissolved solids in solution. It is a useful indicator to determine if the supply is being contaminated from another source (e.g. an illegal connection). Conductivity is also a good measure of salinity (salt content), which affects the potential dissolved oxygen levels in the water. In addition, it is used as an indicator of how ion-free or impurity-free the sample is; the purer the water, the lower the conductivity. Having said that, totally pure water is insipid and is potentially harmful, so a zero reading of conductivity would not be desirable. Conductivity is measured in micro Siemens per centimetre (μS cm-1), where Siemens is the unit of electric conductance. There is no human health risk associated high with Conductivity. In the Drinking Water Regulations it is defined as an Indicator Parameter.

What is an exceedance of Conductivity? 
The designated limit for Conductivity in the EU drinking water directive is 2500μS/cm. Therefore any result above this level is an exceedance for Conductivity.

How can an exceedance of Conductivity occur? 
Conductivity in freshwater systems is affected by the geology of the area through which the water flows. Streams that run through granite bedrock will have lower conductivity, while those that flow through limestone and clay soils will have higher values. High readings can also come from industrial pollution or run-off from roads. Extended dry periods and low flow conditions also contribute to higher conductivity readings.

How are Conductivity exceedances dealt with?
All Exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Free Chlorine? 

The addition of chlorine to drinking water is an essential and critical step in the water treatment process. It ensures that any harmful bacteria that may have passed through the treatment process are killed, but in addition it ensures that the treated water remains disinfected right up to the customer's tap. When chlorine is added to the water, some of it binds to organic and inorganic particles, making it unavailable for disinfection. However the remaining proportion of chlorine that is not bound to anything in the water is called Free Chlorine and this is available to kill off any bacteria.

What is an exceedance of Free Chlorine?

There is no minimum regulatory limit for Free Chlorine, however the EPA recommend that there should be at least 0.1mg/L of Free Chlorine in drinking water throughout the entire distribution network. Therefore any result below 0.1mg/L could be interpreted as an "exceedance". Likewise there is also no upper regulatory limit for Free Chlorine, however the World Health Organisation has recommended a conservative upper guideline value of 5mg/L. Drinking water with this amount of chlorine would most likely have an unacceptably strong chlorine taste and smell. Uisce Éireann endeavours to maintain chlorine levels within the distribution network at levels above 0.1mg/L but not above levels that would render the water unacceptable to our customers in terms of taste and odour. The average chlorine level across all our supplies is maintained between an approximate range of between 0.3 - 0.5mg/L.

How can low Free Chlorine levels occur?

There are a number of factors which can cause Free Chlorine levels to fall below the minimum EPA recommended limit of 0.1mg/L. Chlorine decays over time, therefore the longer the water remains in the distribution network, the lower the chlorine levels will fall. Any sections of the distribution network with sluggish or slow flows may increase the water "age" and therefore reduce the amount of remaining Free Chlorine. Other factors which may cause Free Chlorine levels to drop below recommended levels might include a chorine dosing fault at the treatment plant or chlorine boosting station, the condition of the water mains (e.g. water passing through old cast iron mains can reduce chlorine levels), contamination incidents, burst mains etc.

How are low Free Chlorine levels dealt with?

Uisce Éireann has online monitors installed at every site where chlorine is dosed. These monitors measure chlorine levels on a continuous basis and are alarmed to alert the plant operator if chlorine levels fall below (but also above) defined threshold levels. In addition to online monitoring, plant operators undertake manual spot testing of chlorine levels at dedicated locations in the distribution network. This provides an additional level of assurance that the water is being properly disinfected. Where either online monitoring or manual spot testing indicates that chlorine levels are insufficient this will trigger an operational response which can include actions such as checking the chlorine dosing system, increasing the chlorine dose, flushing the network etc.  

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Hydrogen Ion concentration (pH)?
Hydrogen ion concentration is better known as pH and is a measure of whether a liquid is acidic or alkaline. The pH scale ranges from 0-14. Water with a pH of seven is neutral, below seven is acidic (getting more and more acidic as it approaches pH 0), and above seven is alkaline (getting more and more alkaline / caustic as it approaches pH 14). Low pH (that is less than 6.5) can have a corrosive effect on certain pipes, e.g. Lead pipes and Copper pipes, which can increase the concentrations of these metals in drinking water. Extremes of pH can also affect the palatability / taste of water. In the Drinking Water Regulations pH it is defined as an Indicator Parameter.

What is an exceedance for pH? 
The Drinking Water Regulations sets a low limit of no less than pH 6.5 and a high limit of no higher than pH 9.5. Therefore any result above or below this specified range is an exceedance for pH.

How can a pH exceedance occur?
The typical pH range of drinking water in our public supplies is between 6.8 and 7.4. Some sources have naturally low pH levels due to soil, rock, and geology type in the catchment area of the source. In some cases, the pH of the water can dip below the lower regulatory limit of 6.5. Sources with a naturally high pH are very rare. Some treatment plants undertake pH correction of the final water to bring the pH up to above 7.0. Any occurrence of high pH may be due to an operational issue with the pH correction process.

How is a pH exceedance dealt with? 
One of the first items to be investigated where low or high pH is detected is whether pH correction is in place at the treatment plant. If so then the correct operation of this system is investigated and verified. As outlined above one of the issues associated with low pH is the corrosive effect on Lead and Copper pipes. This can result in these metals dissolving into the drinking water. Therefore follow up investigations following low pH levels typically include testing the water for these metals. Supplies with persistent pH issues are brought to the attention of the HSE and EPA, and are kept fully informed of how investigations are progressing and what corrective actions are being undertaken.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Oxidisability?
This measures the organic content of water but is rarely tested in drinking water as the Total Organic Carbon test is deemed to be a more representative of the carbon content. Generally the parameter Total Organic Carbon is analysed instead of Oxidisability.  In the Drinking Water Regulations it is defined as an Indicator Parameter.
 
What is an exceedance for Oxidisability?
The limit set out in the EU drinking water directive is 5.0mg/l. Therefore any result above this level is an exceedance for Oxidisability.
 
How would an Oxidisability exceedance occur?
Exceedances of this parameter could indicate poor filtration practices or a pollution event at source.
 
How are Oxidisability exceedances dealt with?
All Exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.   

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is pH?
pH stands for Hydrogen ion concentration and is a measure of whether a liquid is acidic or alkaline. The pH scale ranges from 0-14. Water with a pH of seven is neutral, below seven is acidic, and above 7 is alkaline. Extremes of pH can affect the palatability of water. In Drinking Water Regulations it is defined as an Indicator Parameter.

What is an exceedance for pH? 
The limit value set out for pH in the EU drinking water directive is a designated range of > 6.5 - 9.5 pH units. Therefore any result above or below this specified range is an exceedance for pH.

How can a pH exceedance occur?
Low values indicate excessive acidity in a water supply whereas high values indicate excessive alkalinity. This is one of the more stable parameters, therefore, a change in the pH value of water would be immediately investigated as it could indicate a major event.

How is a pH exceedance dealt with? 
All Exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Total Chlorine? 

The addition of chlorine to drinking water is an essential and critical step in the water treatment process. It ensures that any harmful bacteria that may have passed through the treatment process are killed, but in addition it ensures that the treated water remains disinfected right up to the customer's tap. When chlorine is added to the water, some of it binds to organic and inorganic particles, making it unavailable for disinfection. This is call Combined Chlorine. The remaining proportion of chlorine that is not bound to anything in the water is called Free Chlorine and this is available to kill off any bacteria. Total Chlorine is the sum of Combined Chlorine (proportion of Total Chlorine not available for disinfection) and Free Chlorine (proportion of Total Chlorine available for disinfection). The Total Chlorine level in drinking water will always be at least the same if not greater than the Free Chlorine level.

What is an exceedance of Total Chlorine?

There is no minimum regulatory limit for Total Chlorine, however the EPA recommend that there should be at least 0.1mg/L of Free Chlorine in drinking water throughout the entire distribution network. Therefore any result below 0.1mg/L could be interpreted as an "exceedance". Likewise there is also no upper regulatory limit for Free Chlorine, however the World Health Organisation has recommended a conservative upper guideline value of 5mg/L. Drinking water with this amount of chlorine would most likely have an unacceptably strong chlorine taste and smell. Uisce Éireann endeavours to maintain chlorine levels within the distribution network at levels above 0.1mg/L but not above levels that would render the water unacceptable to our customers in terms of taste and odour. The average chlorine level across all our supplies is maintained between an approximate range of between 0.3 - 0.5mg/L.

How can low Total Chlorine levels occur?

Free Chlorine is the proportion of Total Chlorine which is available for disinfection, therefore low levels of Free Chlorine are viewed as an "exceedance". There are a number of factors which can cause Free Chlorine levels to fall below the minimum EPA recommended limit of 0.1mg/L. Chlorine decays over time, therefore the longer the water remains in the distribution network, the lower the chlorine levels will fall. Any sections of the distribution network with sluggish or slow flows may increase the water "age" and therefore reduce the amount of remaining Free Chlorine. Other factors which may cause Free Chlorine levels to drop below recommended levels might include a chorine dosing fault at the treatment plant or chlorine boosting station, the condition of the water mains (e.g. water passing through old cast iron mains can reduce chlorine levels), contamination incidents, burst mains etc.

How are low Total Chlorine levels dealt with?

Uisce Éireann has online monitors installed at every site where chlorine is dosed. These monitors measure chlorine levels on a continuous basis and are alarmed to alert the plant operator if chlorine levels fall below (but also above) defined threshold levels. In addition to online monitoring, plant operators undertake manual spot testing of chlorine levels at dedicated locations in the distribution network. This provides an additional level of assurance that the water is being properly disinfected. Where either online monitoring or manual spot testing indicates that chlorine levels are insufficient this will trigger an operational response which can include actions such as checking the chlorine dosing system, increasing the chlorine dose, flushing the network etc.  

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Total Indicative Dose?
Total Indicative Dose is a measure of the current amount of radiation the body receives from the consumption of treated water. This is a measurement of combined radioactivity (i.e. gross alpha and/or beta activity) from several natural substances, including potassium-40, lead- 210 and radium-228, artificial radionuclides such as caesium-137 and strontium-90, as well as tritium, which can be both natural and man-made. Total indicative dose is measured in Sieverts (Sv), where 1 Sv = 1 Joule/kg. In drinking regulations it is defined as an Indicator parameter.
 
How would an exceedance of total indicate dose occur?
An exceedance in the total indicative dose might point to natural problems underlying the source (e.g. uranium in the local bedrock and soils), or contamination due to human activity.
 
What is an exceedance of total indicative dose?
The limit designated in the EU drinking water directive for tritium is 0.10mS v/year. Therefore any result above this level is an exceedance for Total indicative dose.
 
How is an exceedance of total indicative dose dealt with?
All Exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is total organic carbon?
Total organic carbon (TOC) is a measure of the total amount of organic carbon in water which generally comes from decaying vegetation. As a measure of water quality, it provides an indication of the potential for the regrowth of bacteria in reservoirs and distribution systems. TOC is very important in measuring the amount of organic matter in the water supply. In the Drinking Water Regulations it is defined as an Indicator parameter.
 
What is an exceedance of TOC?
The EU drinking water directive does not specify a limit for this parameter, however it does specify that no abnormal change should occur.
 
How can an exceedance of this parameter occur?
The presence of indicates the presence of natural decaying matter in the water supply. A sudden or abnormal increase in TOC may indicate a pollution event.  
 
How is an exceedance of TOC dealt with?
All exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Tritium?
Tritium is a naturally occurring radioactive substance which is formed in the upper atmosphere due to the bombardment of atmospheric gases by high energy cosmic rays. Tritium is measured in Becquerel's per litre (Bq/l), a Becquerel being an international unit to measure the activity of a radioactive nuclide. Tritium is used commercially as a light source in flares, emergency lights, exit signs and luminous dials. In drinking regulations it is defined as an Indicator parameter.
 
What is an exceedance of Tritium?
The limit for Tritium set out in the EU drinking water directive is 100 Bq/l.  Therefore any result above this level is an exceedance for Tritium.
 
How can an exceedance of Tritium occur?
The presence of tritium in drinking water might suggest a pollution event. The monitoring of Tritium is only necessary if tritium is found to be present in the locality and it cannot be shown by other means that the level of tritium is well below 100 Bq/litre.
 
How is an exceedance of Tritium dealt with?
All Exceedances of drinking water parameters are reported to the EPA and also the HSE where necessary. Drinking water parameter exceedances are fully investigated to determine the cause and appropriate corrective actions are implemented.

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Turbidity?
Turbidity is a measure of the "cloudiness" of the water which can be caused by tiny air bubbles or finely suspended particles. It can be caused by a disruption to residue in the mains or can be due to poor water quality. There is no defined limit for Turbidity at the customer's tap under the Drinking Water Regulations however a guideline limit of 4NTU (Nephelometric Turbidity Units) is generally used.  The cloudiness of water is typically caused by tiny particles that are suspended in the water. Turbidity is measured in Nephelometric Turbidity Units (NTU) and water below 4NTU will be visibly clear to the human eye. Turbidity is an indicator parameter for drinking water. In drinking regulations it is defined as an Indicator parameter.
 
What is a Turbidity exceedance?
The limit for Turbidity in drinking water leaving a surface water treatment plant is 1NTU (Nephelometric Turbidity Units). However, for drinking water samples tested at the point of compliance (which is typically the kitchen tap), the limit is aesthetic. A general guideline limit of 4NTU for aesthetic purposes is recommended.
 
What causes a Turbidity exceedance?
Exceedances for Turbidity can be due to disruption of sediment in cast iron mains or can also indicate that the water treatment process may not be operating effectively.
 
How are Turbidity exceedances dealt with?
All exceedances for Turbidity are notified to the HSE and Uisce Éireann consults with them to seek their advice in relation to the protection of public health. Turbidity exceedances are also notified to the EPA where there may be a risk to public health, or where the exceedance indicates a persistent issue. Turbidity exceedances are fully investigated to determine the cause and suitable corrective actions (e.g. regular flushing of mains) are taken. 

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency

What is Turbidity?
Turbidity is a measure of the "cloudiness" of the water. Turbidity can be caused by disruption to sediment in the mains or can be due to deterioration in water quality. Turbidity is measured in Nephelometric Turbidity Units (NTU) and water below 4NTU will be visibly clear to the human eye. Turbidity is an indicator parameter for drinking water. In drinking regulations it is defined as an Indicator parameter.
 
What is a Turbidity exceedance?
The limit for Turbidity in drinking water leaving a surface water treatment plant is 1NTU (Nephelometric Turbidity Units). However, for drinking water samples tested at the point of compliance (which is typically the kitchen tap), the limit is aesthetic. A general guideline limit of 4NTU for aesthetic purposes is recommended.
 
What causes a Turbidity exceedance?
Exceedances for Turbidity can be due to disruption of sediment in cast iron mains or can also indicate that the water treatment process may not be operating effectively.
 
How are Turbidity exceedances dealt with?
All exceedances for Turbidity are notified to the HSE and Uisce Éireann consults with them to seek their advice in relation to the protection of public health. Turbidity exceedances are also notified to the EPA where there may be a risk to public health, or where the exceedance indicates a persistent issue. Turbidity exceedances are fully investigated to determine the cause and suitable corrective actions (e.g. regular flushing of mains) are taken. 

For further information on this drinking water parameter and others please visit the following websites:

World Health Organisation
Health Service Executive
Environmental Protection Agency