More than 700 customers in the South Sligo have been removed from the Lough Talt Boil Water Notice.
Irish Water say those customers in the Bellaghy area are now receiving clean water, which they no longer need to boil before consumption.
Irish water says the 785 Bellaghy customers removed from the Boil Water Notice are now getting clean, safe water from the Charlestown public supply.
Those customers will remain on that supply until further notice.
The areas removed from the Boil Water Notice include Bellaghy, Sandyhill, Cloonaughill, Cully, the southern 80% part of Bunnacrannagh, Brackloonagh, Brogher, Lissard and Curryfuel.
Irish Water says it will telephone or write to the customers in the Bunnacrannagh area who are being removed from the Boil Water Notice.
However, it adds that customers who live in this area are advised to keep boiling water before consumption until they receive either a call or a letter.
Meanwhile, all remaining customers on the Lough Talt scheme must continue to boil their water until further notice, a situation that has now existed for almost four months.
There were over 13,000 affected by the notice put in place at the start of February.