Around one hundred thousand people will be without water in certain Dublin areas for the rest of Saturday.
Works had to be completed on a major leak to water main pipes in Dublin 2 and Dún Laoghaire Rathdown.
They are expected to be completed by Saturday evening.
Speaking to 98FM, Irish Water's Regional Operations Manager John O'Donoghue said:
"This is quite a substantial leak that we have on the trunk main coming from Stillorgan going all the way in to the city," he said.
"The pipe itself is down quite a distance, it's two and a half meters to the top of the pipe so it's quite a major operation.
"It's in the middle of a bus lane as well on the outward bound bus lane on the Stillorgan road.
"There's quite a lot of planning involved and disruption in terms of traffic, but obviously we're most conscious of all of the disruption to householders."