WATER is being cut off or seriously reduced across Dublin at night due to a big supply shortage despite reservoirs being at capacity.
A harmless algae in the water has cut production at a treatment plant from 70 million litres a day down to just 40 million litres, sparking rationing for tens of thousands of householders.
The rationing affecting homes and businesses, including bars and restaurants, has also been caused by an increased number of leaks from pipes caused by the unseasonal cold snap.
The algae, which does not affect the safety or quality of the treated water, has reduced the flow of water in the plant's filtration system.
The restrictions, from 10pm to either 7am or 9am, started last night and will continue over Easter until at least next Tuesday when the situation will be reviewed.
Dublin City Council said the nightly restrictions, involving loss of pressure and possible loss of supply, are needed to replenish treated water levels.
The reservoirs of raw water are still high and the problem centres on the production and supply of treated water.
The council said the restrictions were being imposed because the unseasonal weather had increased leakage, and a production problem at the Roundwood Water Treatment Plant.
There was also an increased demand for water over the cold snap, although the council was not in a position to quantify the increase.
The rationing will apply across Dublin city and the suburbs in its council area, but will not affect householders in Fingal, Dun Laoghaire and South County Dublin council areas.
"Some people will see a loss of supply during the night," a city council spokesman said.
"We will be reducing pressures throughout the system over the weekend in order to conserve supplies.
"People may notice reductions in pressure or loss of supply throughout the entire city," the spokesman added.
The council apologised for any inconvenience caused and said it would do everything possible to minimise their scale and duration.
"We are asking consumers to bear with us while we work to restore the water supply to normal," a statement added.
The council is urging consumers all over the city to conserve water this weekend, to help restore levels in water reservoirs to normal.
Council crews are repairing any breaks to the public mains as they arise.
The council urged members of the public to report any location where they see water rising or running over the ground.
In such an event they can call the emergency telephone number 01-6796186 outside office hours.
"It should be stressed that there is no problem with the quality of treated drinking water or with storage levels of untreated/raw water.
"We are asking people to visit www.taptips.ie for easy water- saving tips."