Up to 1,000 local homes and business on the Ardfinnan Water Supply Scheme are experiencing low pressure and intermittent service due to a large leak.
It means levels are dropping in the Jamestown reservoir and is likely to affect the areas around Poulmucka, Ballyclerihan, Red City, and Barrettstown.
Uisce Éireann says a tanker is available as an alternative supply at Poulmucka village but you’d need to bring your own containers and to boil the water as a precaution.
Repair crews are trying to sort the problem but it’ll take two to three hours for normal supply to fully return after they find and fix the leak.
It’s hoped it will be resolved by tomorrow morning (Wednesday).