Above the allowable limit of pesticides has been detected in drinking water 81 times this year.
The detections impacted 32 different water supplies, with the Environmental Protection Agency (EPA) taking enforcement action on each occasion.
Pesticides are often used by farmers to clear unwanted material from their lands, but they can also be used for domestic use, sometimes making their way into water supplies.
Irish Water has tested water supplies nearly 24,000 times this year to see if they had above the allowable limit.
The impacted supplies were detected in multiple counties, including Carlow, Louth, Wexford, Donegal, Tipperary, Monaghan and Limerick.
One of the common pesticides detected was glyphosate, which is often used in weed killers.
John Leamy, drinking water compliance lead with Irish Water, says the findings are not dangerous to people's health.
"An important message to understand in relation to these failures is there is no threat to public health and Irish Water notify the HSE every time we detect a failure for pesticide.
"If public health was in jeopardy, we would impose a 'Do Not Consume' notice on the effected water supply and this has never happened in Ireland to date."
Irish Water says it wants to reduce the risk posed by pesticides by raising awareness and through engagement and collaboration.
