Up to 1,800 people in Corofin town, Co Clare, and its environs in Ruan village will be unable to drink tap water over the weekend.
The customers of the Corofin and Ruan Public Water Supply in County Clare, as well as customers of the Killeen Group Scheme Supply are affected by the alert.
The water is not suitable for drinking due to the presence of an algal bloom at Inchiquin Lake which has arisen due to the extended period of dry weather, elevated temperatures and reduced water levels in the lake.
The HSE, in conjunction with Irish Water and Clare County Council, has advised that tap water should not be used until further notice except for the flushing of toilets, flushing of internal house plumbing systems and laundry.
Customers have also been told to discard ice cubes in fridges and freezers and that the water should not be used for showering, brushing teeth, etc.
The council said that works will continue over the weekend to connect some of the affected customers to an alternative water supply.
Drinking water tankers are being provided at the following locations from today to Monday:
Outside Bofey Quinns Pub, Corofin
St. Patricks Community Hall, Gort Road, Corofin
Opposite Kerry Agri at the Ennistymon Junction, Corofin
Grotto in Corofin town
Adjacent to the Dalcassion pub in Ruan village