The army has been called in to help tens of thousands of homes and businesses in Louth and Meath who remain without water five days after a burst pipe.
Defence Forces have been asked to help provide alternative supplies, as Irish Water warns that it could be the weekend before supply returns to normal.
Northern Ireland Water has dispatched tankers to help transport water to those affected in the Drogheda and surrounding areas.
Water tankers and containers have also been mobilised across the country to replenish water supplies.
Repair work has been ongoing at Staleen Water Treatment plant since Friday when a pipe burst.
Irish Water said the repair work has proven more challenging than initially thought.
Up to 60,000 households and businesses have been affected. Reservoir levels have also been left "critically low".
In order to manage the remaining water, a programme of rationing will continue in the affected areas.
Our Lady of Lourdes Hospital in Drogheda has been prioritised in order to maintain supply to patients.
Temporary water stations have been set up as shops have been running low on bottled water.
Earlier on Tuesday, Irish Water managing director Jerry Grant said the complexity of the piping meant it had not been possible to carry out the repairs in the normal timeframe.
In a statement, the company said it hoped to complete the repair by Thursday but added that when the water main is repaired it could take a number of days before full supply is restored.
Thirty-three road tankers from across the island have been deployed to supplement the mains water supply, to replenish temporary water stations and to supply priority customers. More than 90 water containers are in place across Louth and Meath.