More than 100,000 people have been left without safe drinking water in the wake of yesterday's ferocious Atlantic storm, it is feared.
With 190,000 homes and businesses still without power, mostly across the south and west, Limerick County Council was forced to order a widespread boil water notice as a precaution.
Electricity supply chiefs in ESB had earlier warned that repairing power cuts to major infrastructure - such as water treatment plants - were one of its top priorities.
Limerick County Council said the boil notice was a precaution on the advice of the Health Service Executive and Irish Water.
"The council is not in a position to guarantee that water supplies throughout the county are treated to the standards required by regulations," a spokesman said.
Water supplies in Limerick city and suburbs under the authority of the county council are not affected by the notice.
The County Council will continue to liaise with health chiefs with a view to lifting the boil notice as soon as practicable but it is likely to remain in place for a number of days.
The warning called for all water to be boiled rigorously if it is for drinking; for preparing foods not to be cooked; for brushing of teeth; and for making ice.
Limerick County has a population of 135,000 but it is not clear exactly how many homes and businesses are facing the boil notice.
Also in the west, Clare County Council has begun sending tankers of water to five towns after shortages in supplies in and around Sixmilebridge, Cratloe, Kilmurry, Kilkishen and Killaloe.
"The council is in ongoing engagement with the ESB and Irish Water, who have confirmed that they are working to address the issue," a spokesman for the council said.
Limerick city has been unaffected with areas under the authority of the County Council such as Dooradoyle, Raheen and Castletroy and university not including in the boil notice.
Meanwhile, ESB warned some customers could be without power for two or more days as repairs focus initially on high voltage lines.
Helicopters have been deployed by the electricity company as 2,000 repair staff search for the worst-hit areas, supported by crews from Northern Ireland and outside contractors.
Power has been restored to over 95,000 customers since the peak of the storm yesterday, the ESB said.
Power chiefs said repairing dangerous faults and making them is priority before faults can be repaired to restore supply to the larger number of homes and businesses.
Some 60,000 people are also without telephone and communications at their homes and businesses.
West Cork and Kerry have been singled out as the two regions which bore the brunt of the weather system which saw near record winds gusting to 177km/h inland.
ESB said its crews were working through driving rain and difficult conditions with the focus on supplies in Kerry, Cork, Limerick, Tipperary, Wexford, Waterford, Clare, Laois.
Helicopters have flown out of Dungarvan, Co Waterford and Kilcullen, Co Kildare to examine lines and assess the damage to the network.
The aerial patrols were tasked to traverse the south of the country, from the south-east towards Limerick and Clare, and into Cork and Kerry.
The Government's National Coordination Group met this morning to review the damage done to communities up and down the country and to transport and energy services.
"ESB have advised that it deployed 2,000 staff to deal with power outages, and it could take a number of days to restore power to all areas as some of the infrastructure is in remote areas and access problems may hinder them," the unit said.
Repair teams have been tasked to prioritise power to major infrastructure such as water treatment plants and pumping stations as these facilities can cause public health issues first.
High voltage supply lines are also top of the agenda before works begin on the more local supply chain.