A Boil Water Notice affecting over 600,000 people for the last eight days has been lifted "with immediate effect".
The HSE, Irish Water and Fingal County Council confirmed this evening that customers supplied by Leixlip Water Treatment Plant can once again drink their tap water.
The Environmental Protection Agency (EPA) carried out an audit of the old plant on November 8 and it returned "satisfactory results".
This was a factor in the decision to lift the notice, the organisations said in a joint statement.
The joint statement added: "Irish Water and Fingal County Council were on site to support the audit and the HSE were also present.
"The EPA, who are expected to publish their findings next week, were able to see the ways in which Irish Water and Fingal County Council have optimised the old plant; the additional staffing and monitoring; and daily water testing.
"Irish Water, the HSE, EPA and Fingal County Council will continue to liaise on the Leixlip Water Treatment Plant, the protection of public health being the number on priority."
Niall Gleeson, Managing Director of Irish Water, said: "Irish Water acknowledge and understand the impact of this boil water notice on the 600,000 people affected and we sincerely regret the inconvenience.
"We endeavoured to keep the public up to date at every stage and we are grateful to the media, elected representatives and members of the public who shared the information on social media and who supported family, friends and neighbours.
"We are grateful to our partners in Fingal County Council who worked with us to provide all of the necessary information to the HSE and EPA to facilitate the lifting of this boil water notice.
"The old plant at Leixlip remains vulnerable and Irish Water working with Fingal County Council will be working to minimise the risk of another Boil Water Notice. We have maximised the processes to build resilience while also diverting water from Ballymore Eustace, the country’s biggest water treatment plant, to decrease pressure on the old plant at Leixlip. Working with Fingal County Council we are increasing the monitoring and staffing at the plant while also increasing the water testing. The ultimate solution is to replace the filters at the old plant and this process is being accelerated as quickly and safely as possible while still maintaining supply to the greater Dublin area.
"If we could, we would shut down the old plant, take it off line and do all the refurbishment at once. This is not possible because 20% of Dublin’s water supply comes from the Old Plant and we do not have the spare capacity to allow this to happen.
"We will continue to monitor the plant closely."
It is recommended that those with a compromised immune system discuss with their doctor about the need to always boil their drinking water, regardless of the source of supply.
Detailed advice is available at: https://www.hpsc.ie/a-z/gastroenteric/cryptosporidiosis/publications/File,14628,en.pdf
In general, symptoms of cryptosporidiosis and giardiasis begin about two to 10 days after being exposed to a source but may take up to 28 days. People who are unwell should contact their GP.
Customers with questions can contact Irish Water directly on their 24/7 customer helpline at 1850 278 278.
Updates are also available on the Water Supply Updates section on the website water.ie and on Twitter @IWCare.
