Irish Water has issued a warning to farmers about the use of pesticides and Carlow is on a watch list.
The utility says a file on the matter was opened last year in relation to the Carlow Town supply after Metaldehyde was detected.
Water for the supply is drawn from the River Burrin and the Oak park borehole.
Irish Water say the pesticide levels detected in the water supply does not pose any immediate risk to health.
However they say it is imperative that users of pesticides in these areas are mindful of best practice when spraying their lands.
There is currently no file open on Kilkenny but there was concern previously in relation to the Troyswood supply.