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Uisce Éireann confirms commitment to keep the public informed about THMs and other water quality issues

09 April 2024

Information below is relevant until further updates are provided here or on our Supply and Service Updates section.

Uisce Éireann continues to prioritise the elimination of trihalomethanes (THMs) from public water supplies through a proactive campaign of targeting, testing and remediating any supplies where THMs are present. We remain committed to keeping the public informed about the presence of THMs in supplies on the Environmental Protection Agency’s Remedial Action List (RAL).

Overall water supplies in Ireland are excellent, the most recent EPA report published last year, demonstrates that public drinking water is safe to drink (99.7% compliant with chemical and bacterial limits).

Information booklets were previously issued by Uisce Éireann to all customers identified as being on supplies where THMs were present. The communications issued were approved by the Environmental Protection Agency and HSE, and we have continued to provide updates to customers on water quality issues as they arise. Uisce Éireann is engaging with both agencies in relation to further communication with customers on public water supplies that are on the Remedial Action List. This information will be in addition to the detailed information currently available on the Uisce Éireann, HSE and EPA websites. We will provide further details and timelines in relation to any additional communications in due course.

The vast majority of public water schemes identified in the recent judgement of the European in relation to THM exceedances have now been addressed, with just 5 of the original 74 schemes remaining. And projects are underway at all five locations to address the issues either through upgrades or rationalisation of existing treatment plants.

Uisce Éireann’s enhanced testing and monitoring programme across its 700-plus public water supplies has enabled the utility to identify 25 schemes on the Remedial Action list for THMs. In all these cases we are taking concerted action to address these risks through a combination of plant upgrades and enhanced operational controls.

It is important to reassure customers on these remaining schemes that water is safe to drink. THMs are chemicals which are formed by the reaction of naturally occurring dissolved organic material in the water and chlorine, which is used for disinfection purposes. Chlorination is an essential step in the production process to ensure harmful bacteria are eliminated from your drinking water. The clear advice from the HSE in relation to THMs and drinking water is that the "benefits of using chlorine to treat our drinking water are much greater than any possible health risk from THMs". This is also the position of the World Health Organisation (WHO) which states that “...adequate disinfection should never be compromised to control THMs".

When our monitoring programmes detect THM levels above the allowable limit (100µg/L), Uisce Éireann notifies the Environmental Protection Agency and consults with the Health Service Executive (HSE). To date, a Do Not Drink notice has not been imposed on any public water supply due to THM exceedances.

In the meantime, customers can find out more about their local public water supply, including test results for a range of drinking water parameters, on the Uisce Éireann website at