Two private water supplies in Kerry were found to have failures with trihalomethanes (THMs) standards last year.
The Environmental Protection Agency has released its Drinking Water Quality in Private Schemes and Small Private Supplies report.
It found failures with THMS in Kells and Tousist; this is a chemical substance which forms when natural material in the water source, such as vegetation, reacts with chlorine in the disinfection treatment process.
Last year, 16 private group schemes and one small private supply nationally had such a failure.
The EPA report covers over 380 group water schemes, supplying water to around 200,000 people.
Overall, it found urgent action is required to improve the quality of private drinking water provided by these schemes and supplies.