A new report from the Environmental Protection Agency shows that, while the quality of drinking water in public supplies across Mayo remains high, two water supplies in the county were on the EPA's Remedial Action List at the end of 2019.
The Newport Public Water Scheme, which has ongoing levels of pesticides, and the Ballycastle scheme, which has inadequate treatment for cryptosporidium, are among 52 water supplies listed nationally, supplying drinking water to over one million people, that are "vulnerable to failure", the EPA has warned.
The completion date for the Ballycastle scheme is next month - August 2020 - while in Newport, the EPA direction to Irish Water requires compliance by December 2021.
Meanwhile there are 17 water supplies across the country currently on a boil water notice - including the Lough Talt Regional Water Supply in Sligo which affects over 12, 500 customers.
A boil water notice was issued for the Lough Talt supply in January 2019 due to cryptosporidium, and remains in place currently.
An action plan for improving the water quality in Lough Talt is in place, and is due for completion by the end of this year.
The EPA report also says a slowdown in replacing lead pipes means Irish Water's plan to remove all lead from public water supplies by 2026 could take 60 years.