Around 13,000 people are affected by a boil water notice that has been issued for a regional supply scheme in Co Sligo.
The notice has been issued for people served by the Lough Talt Regional Water Supply Scheme due to the detection of cryptosporidium in treated water.
The Lough Talt scheme supplies the towns of Tubbercurry and Ballymote, as well as a large rural hinterland including the villages of Annagh, Aclare, Curry, Lavagh, Ballanacarrow Carroweden, Kilmacteige and Coolaney.
Irish Water has said it will be carrying out weekly sampling at a number of sites in the scheme.
It said the notice will be lifted if there were sufficient clear samples over a number of weeks.
However, it added that if further cryptosporidium detections are made the notice will be extended and may require the construction of a new treatment plant.
