A boil water notice has been issued by Irish Water for parts of Wicklow and South Dublin, affecting some 65,000 people.
The warning was announced as a precautionary measure following a mechanical failure of the chlorine booster at Vartry Water Treatment Plant.
All water treatment at the plant must have adequate chlorine levels added to the water to make it safe to drink.
Areas supplied by the Vartry Water Treatment Plant affected in Co Wicklow are:
Ashford, Newcastle including Newcastle Hospital, Newtownmountkennedy, Kilcoole, Kilquade, Kilpedder, Kilmacanogue including Glenview Hotel/Kilmurray Cottages, Greystones, Cookstown Road, Fassaroe/Berryfield Lane, Kilcroney, Delgany and Bray.
Areas in Dublin affected include:
Corke Abbey, Woodbrook Glen, Old Connaught Avenue, Thornhill Road, Ballyman Road, Ferndale Road from its junction with Old Connaught Avenue to Allies River Road, the Dublin Road from the junction of Old Connaught Avenue to Allies River Road, and all areas off these roads.
In a statement Irish Water said:
“Irish Water will liaise with the HSE with a view to having the Boil Water Notice removed as soon as possible.
“Irish Water are carrying out chlorine dosing on the supply today and have put in place a water sampling programme to test the chlorine levels in the impacted areas.
“In the meantime, all customers of this supply are advised to boil water before use until further notice.”