Thousands of households were left without water in north Kerry due to a pump failure at Listowel Regional Water Treatment Plant.
However the pump has been repaired and Irish Water hopes to begin restoring supply later on Monday.
The areas affected include Listowel, Moyvane, Knockanure, Lisselton, Finuge, Lixnaw.
Senior officials from Irish Water and Kerry County Council are on location and are monitoring the situation while alternative water supplies have been diverted to the local hospital and where possible to other businesses in the area.
The Civil Defence continues to distribute bottled water to vulnerable customers, man water stations and assist with the distribution of information leaflets to homes and businesses.
Margaret Attridge, operations manager with Irish Water told RTÉ's Morning Ireland on Monday: "For most of the day yesterday from approximately midday on, there were 4,000 affected by the water outage in Listowel.
“This had the potential to be a lot more but we mobilised tankers to fill reservoirs on the network to maintain supply to places like Ballybunion.”
The pump failure occurred on Saturday night while Irish Water has said restoration will depend on the progress of repair work.
“We got the pump back to site yesterday [SUNDAY]evening and into the operation in the early hours of this morning,” Ms Attridge added.
“It has held and has been pumping all night. It will take some time for reservoirs to get to a level where we can turn into supply.
“As the morning goes on we are hoping, if the pump keeps pumping, slowly over the day we can start opening the valves and restore water to different areas of the network.”
Customers who currently have a supply are asked to conserve their supply. A statement from Irish Water said: “Our customer care helpline is open 24/7 and we would encourage any vulnerable customers who are not registered with us to contact us on 1850 278 278 for further information.
“Irish Water urges people to check in on neighbours and family, particularly the elderly at this time.”
