Irish Water says it has repaired a water pipeline that serves thousands of homes in Drogheda, Co Louth and east Co Meath.
However, the utility says it is continuing to continuing to closely monitor the situation until it is certain the repair is secure.
The pipe is just 20m (65ft) from a similar burst last year, and the latest breach may trigger cuts in supply over the coming days, Irish Water had warned.
The water supply has been maintained for the majority of customers as the treated drinking water reservoir serving Drogheda and most of East Meath has enough water to maintain supply to customers.
Water supply is being maintained to Our Lady of Lourdes Hospital and Irish Water is also prioritising schools, nursing homes, crèches and vulnerable customers.
It has contacted vulnerable customers in Louth and East Meath and Irish Water and Louth and Meath County Councils are coordinating efforts to ensure bottled water is delivered to them today.
A water outage is impacting some customers in Ratoath, Kilbride and Duleek and it could between 36-48 hours before full services is restored for all customers, in particular to properties on higher ground and at the edge of the network. Alternative water supplies have been mobilised and water tankers are located in Ashbourne, Ratoath, Duleek and Kilbride.
Empty containers are available at all water stations in Duleek and Irish Water are distributing empty containers to the other locations.
Previous burst
Last July there was a serious burst in the same pipeline, which led to 80,000 homes and businesses going without water supply for nearly a full week.
A crisis management team has been deployed to the area on standby, to respond immediately if the water supply does run out, or restrictions are put in place.
Repair crews were at the site of the burst main on Wednesday evening, to begin repairs to the pipe.
The burst itself is close to the same stretch of the high pressure water main that reptured last year, which had a huge affect on supply.
“Irish Water has approved the budget and design for a new pipeline to replace the existing lines” in the area, said the spokeswoman.
“We are in the final stages of resolving all of the contractual issues to begin mobilisation of construction of this pipeline within weeks,” she said.
Replaced
Irish Water managing director Jerry Grant said “by the end of the year” the pipeline would be replaced.
"Last year's replacement repair has held, there is no issue with that. But the burst is in the same area," he told RTÉ's Morning Ireland.
“This is a very vulnerable pipe as we know from last year, that is why we’re in the process of replacing it,” he said.
Repair crews worked under lights over Wednesday night and the burst section of the pipe has been removed.
“We’re now accessing the repair, that will take time, it will certainly take today, we’re certainly hoping that within 12-24 hours we’ll have the supply back,” said Mr Grant on Thursday morning.
Local Cllr Kevin Callan has called for a nearby out-of-commission water treatment plant at Rosehall to be brought back into use.
However, it is understood recommissioning the minor treatment plant would require the entire water main to be flushed out. This could lead to boil water notices being required in the short term, according to one source in the Department of Housing.
