Many parts of Dublin and Kildare will be without water this evening as a result of a problem at the Ballymore Eustace waterworks.
The plant, which treats the water supply for most of Dublin and Co Kildare, is understood to have suffered a major mechanical failure earlier this afternoon.
Tens of thousands of households are expected to be affected. Dublin Corporation said the worst hit areas would be Saggart, Tallaght, Jobstown and Ballyboden.
A spokesman said households in these areas may be without water until midnight tonight. He said other areas such as Stillorgan, Rathmines, Rathfarham, Ballyfermot, Walkinstown and Crumlin may experience a drop in pressure.
He said the problem did not affect the quality of the water. Dublin Corporation said it hoped the problem would be fixed by tomorrow morning.