A Do Not Consume Notice has been issued for the Billis/Lavey Group Water Scheme in Cavan.
It's the fifth such notice issued in the Northern Sound region in the past month.
People in the area are being told not to consume their water and instead use alternative supplies - boiling the water will not make it safe to drink.
Water tankers will be available at Lisgrey House and The Lavey Inn for people affected. This water must be boiled before use.
Anyone looking for more information can contact the Billis/Lavey Group Water Scheme on 087 3274178.