Water is slowly refilling a reservoir in the north-east after workers completed the first phase of installing a specially-made pipe to repair a burst main.
The Staleen Water Treatment Plant in Co Meath was yesterday back in production.
Locals in Co Meath and Co Louth have been without water since Friday.
A large metal pipe was lowered more than four metres into the ground to bridge the gap made by the fracture in the existing, 50-year-old main.
Irish Water said water was running through the pipe following the temporary patch.
A permanent fix will be completed in two weeks time - and it could be days before a full water supply is restored.
Meanwhile, calls have been made to reopen a reservoir on the outskirts of Drogheda that was closed two years ago.
Local politicians have said they have no faith that yesterday's repair on the fractured main will provide a long-lasting solution.
Representatives said only the total replacement of the main will provide a permanent fix to secure the region's water supply.
Independent councillor Kevin Callan said Drogheda had suffered a water shortage problem 30 years ago, but at the time had two treatment plants, including one at Rosehall which has now been decommissioned.
"Now we have one treatment plant and the population is five or six times what it was. Irish Water need to open a second treatment plant in Drogheda," Cllr Callan said.
"I was told on Tuesday there was not sufficient manpower in Irish Water to do that and I am absolutely shocked," he added.
"I'm getting several different reasons why they won't open it."
He said these reasons included pH levels, as well as claims that the water isn't safe and that the water level might not be high enough.
"But I'm told reliably by former council staff that plant could be operational within two days. Turn on the filters and the plant is operational," he told the Herald.
"I've no confidence in the statements I'm getting. I was at a meeting on Tuesday with Irish Water with the elected representatives.
"One person said at the start of the meeting Rosehall would not reopen, and later on another person said they will now look at opening it again.
"They have no contingency plan in my view. If they turn on the water after the fix and the pipe fails 6ft down the line, we are back to where we were last Friday," he added.
A statement from Irish Water discounted the option of opening the Rosehall plant.
"The Rosehall reservoir and plant were decommissioned as the raw water source was prone to running dry during summer months and the Staleen Water Treatment Plant had to take over the supply," it said.
In addition to this the source water was identified as having a potential issue with THM's (trihalomethanes), it added.
"As an old plant, Rosehall's treatment processes were also deemed to be insufficient. For these reasons Irish Water is not considering recommissioning the plant," the statement said.
Louth Fine Gael TD Fergus O'Dowd called on the Government to introduce incentives for householders to conserve rainwater.