A boil water notice for almost 600,000 people across parts of Dublin, Kildare and Meath has been lifted.
It follows a consultation with the HSE, Irish Water and Fingal County Council.
The EPA conducted an audit of the Leixlip Water Treatment Plant on Thursday.
The test results of a water sample that was taken earlier in the week was found to be satisfactory.
This lunchtime, Irish Water received the results for two more water samples taken later in the week.
It says that both samples were "satisfactory."
The notice had been in place since Tuesday evening.
Boil Water Notice for customers supplied by the Leixlip Water Treatment Plant has been lifted with immediate effect. We are grateful to our partners in @Fingalcoco who worked with us to provide all necessary detail to the HSE & EPA to facilitate the lifting of this notice. pic.twitter.com/WlipJSCoQg
— Irish Water (@IrishWater) October 25, 2019
Yvonne Harris from 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."
Earlier, the EPA said a blockage in the coagulant dosing line resulted in "operational difficulties" with the water treatment processes - which resulted in elevated turbidity levels in treated water.
It also said there was "a failure to respond to multiple alarms" that activated in response to the elevated levels.