Irish Water is currently working with Mayo County Council to restore normal water supply to impacted customers in North Mayo.
People supplied in the Ballina Town, Moygownagh, Lacken, Ballycastle, Bonniconlon, Kilfian and Killala areas are affected.
It follows a power outage at Lisglennon Water Treatment Plant.
Impacted customers may experience lower than normal water pressure and in some instances, particularly on higher ground, may experience intermittent water outages.
While handwashing remains a priority, Irish Water is appealing to all customers to conserve water as the reservoirs refill.
When Irish Water and Mayo County Council are working to restore normal water supply to impacted customers as quickly and as safely as possible.