Six water supplies in the Shannonside Northern Sound region have had above the allowed limit of pesticides this year.
32 drinking water supplies nationally have been found to exceed the limit.
Irish Water has conducted nearly 24,000 tests in 2020, and there were 81 individual failures across several different counties.
Glyphosate was one of the most common detections noted, and is an ingredient often found in weed killer.
Locally three failures were in the Northern Sound Region.
One was in Cavan in the Belturbet Public Water Scheme and two were noted in Monaghan in Glaslough and Emyvale.
In the Shannonside Region two Leitrim supplies exceeded the limit at North Leitrim Regional and South Leitrim Regional.
There was also a failure recorded in the Longford Central supply.
The Environmental Protection Agency took enforcement action each time, but found there was no risk to people's health.
Dr Michelle Minihan , from the EPA, says pesticides can get into water in different ways: