The Environmental Protection Agency is warning that drinking water in the country's private water supplies is not good enough and is putting people's health at risk.
In its latest Drinking Water Quality report for 2019, the watchdog says more than 100 private supplies failed to meet bacterial standards.
Bacteria in water supplies can make people very ill - particularly young children and the elderly.
1 million people get their drinking water from a private supply, and many more drink water from small private supplies, such as hotels, pubs and restaurants, nursing homes and schools.
Of the 1,418 small private supplies monitored, 88 failed to meet the standards relating to bacteria, while 20 of the 417 private group schemes failed to meet the standards.
The EPA is also concerned that almost one in 5 small private supplies were not monitored in 2019, which makes it impossible to be confident that the water is safe to drink.
In Mayo, 6 of the 37 small private group schemes were not monitored for e-coli.
The report also shows that in 2019, 14 boil water notices were put in place on Mayo schemes, with one Do Not Consume notice -these impacted on almost 2,700 customers.
It also lists 8 private supplies in Mayo with THM failures, or are on the Department's remedial action list.
The EPA says local authorities must ensure than monitoring is undertaken, in line with regulations.
Senior water inspector at the EPA, Dr Michelle Minihan says local authorities need to do more to improve the water quality: