Water disruption throughout large parts of Clonmel is expected to last until 1pm on Saturday.
Irish Water staff are working on a burst 10" main at Highfield Grove, near the by-pass.
Large parts to the north of the town are affected, including the Medical Missionaries nursing home.
An Irish Water statment said essential works to repair the main may cause supply disruptions and low pressure.
Photograph shows work ongoing at Highfield Grove on Friday afternoon
The ares affected are Highfield Grove, Cashel Road, By-pass Road, Ard na Greine, Griffith Avenue, Heywood Road, Knockaun Court, Gurnafleur, Moangarriffe, Powerstown, Rathloose and surrounding areas.
Works have an estimated completion time of 1pm on Saturday.
Anyone contacting Irish Water about the supply and service alert are asked to quote the unique alert reference number - TIP004354