A burst has occurred on a water pipeline serving the Staleen Water Treatment Plant in Drogheda and Meath east.
Irish Water has said that the pipe burst close to the same location as a burst which occurred last July.
At the time, over 80,000 homes and businesses in parts of the northeast were without water for almost a week.
In a statement, Irish Water said that a repair crew is currently assessing the damage and that repairs are due to begin.
It also said that there is enough water to maintain water supply to customers for two days.
However, customers are advised to conserve water until a timeline for resumption of a normal water supply is confirmed.
Irish Water also said that it has mobilised its crisis management team and is hopeful that the repair will be completed in a shorter timeframe.
