Almost 200,000 people could not drink water from their taps at some point last year because of concerns it would make them sick, the Environmental Protection Agency (EPA) said.
The majority were told the water was safe if boiled, but 2,000 were placed under water restriction notices with instructions not to drink it even if boiled.
Of the 66 boil water notices issued, 28 remained in place for more than 30 days. The same applied to 23 of the 34 water restriction notices.
The 40 residents of Whiddy Island in Cork have been unable to drink their water since August 2022.
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Reasons for the notices included the discovery of bugs such as E.coli, cryptosporidium and giardia in the supplies.
Other issues were excessive levels of pesticides, manganese, iron and trihalomethanes (THMs) – chemicals of health concern that form when disinfectant reacts with organic matter in water drawn from rivers and lakes.
Problems have persisted in some places and new issues have arisen, so slightly more than 45,000 people served by 47 supplies in 16 counties are under boil water or water restriction notices.
A further 467,000 people are served by 35 water supplies in 16 counties that are categorised as at risk of contamination and are on a priority list for upgrade or replacement.
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EPA programme manager Noel Byrne said the figures showed significant work was needed on public water supplies.
“It is worrying that almost 200,000 people were affected by water restrictions in 2025,” he said.
“While necessary to protect public health, they are a considerable inconvenience for consumers and point to a lack of resilience in water treatment.”
The EPA’s annual drinking water report shows the overall quality of public supplies remains high, with a compliance rate of over 99 per cent in tests carried out at the country’s 700 water treatment plants, which serve four million people.
But the EPA said water must be safe for consumers to drink every day, so even temporary problems were a cause for concern.
“If a supply is meeting the drinking water standards today and is safe to drink, the supply also needs to be secure to prevent the risk of water quality failures in the future,” the report said.
The 35 supplies categorised as at risk are on the EPA’s remedial action list for priority treatment plant upgrades, but most have been on the list for several years – in one case since 2017 – and are still several years away from works being completed.
They range in size from serving a few dozen people to the Limerick City Environs supply which serves more than 126,000 people.
THMs and general weaknesses in treatment or management processes at the plants are the main concerns cited.
The EPA said Uisce Éireann must take “faster corrective action” where issues have arisen or problems are identified.
Uisce Éireann said in a statement that the number of supplies on the remedial action list was at it lowest, with 10 removed after works were completed during 2025.
“We are proud of the progress made, but we recognise that challenges remain,” said Eleanor Roche, head of environmental regulation.
Of the remaining 35 supplies, 14 are forecast to be either removed from the list or substantially complete and awaiting EPA validation by year end, she said.
The EPA’s report also draws attention to the continuing problem of leaks, with 36 per cent of all treated drinking water lost to leaks.
It said the replacement of lead pipes was also progressing too slowly with only half the 180,000 lead or suspected lead pipes identified in 2017 being replaced or declared safe.
