Irish Water says the problem could continue for a number of days
Irish Water say a boil water notice is in place for some 1,600 people in Co Wicklow.
It says the precautionary measure is due to a mechanical failure of the chlorination system at the Aughrim Annacurra water treatment plant.
The utility says as a result, it cannot guarantee the drinking water entering the supply is adequately disinfected.
It also says the extremely cold weather is hampering repairs.
"This situation could continue for a number of days and a further update will issue tomorrow", Irish Water says.
"As per the instructions of the National Emergency Coordination Group (NECG), to ensure the health and safety of our workers and the local authority staff working in water services, there will be no staff available to respond to water or wastewater emergencies during the red weather warning called by Met Eireann from 4.00pm Thursday March 1st."
"In the meantime, all customers of this supply are advised to boil water before use until further notice."
The water can be used for personal hygiene, bathing and flushing of toilets - but not for brushing teeth or gargling.
It advises that caution should be taken when bathing children to ensure they do not swallow the bathing water.
Irish Water has apologised for the inconvenience caused.
More information and additional advice can be found on the Irish Water 24-hour customer care line at 1850-278-278.