Up to 1,400 homes and businesses in Dublin are being advised not to use their water for drinking or cooking.
A boil notice has been put in place in the north east of the city after a water sample failed a health and safety test.
A map of the affected areas can be found at the website, or by calling 01 679 61 86.
Senior engineer with Dublin City Council, Brian Hennelly, said it could be a few days before the water is deemed safe.