Nitrates were found in just four group water schemes and 20 small private supplies which were monitored for nitrates in 2019.

Some 349 group water schemes were monitored for nitrates, while 650 small private supplies were monitored.

Overall, the latest report from the Environmental Protection Agency (EPA), shows results from 417 private group schemes and 1,418 small private supplies monitoring various types of pollution.

Nitrates entering a water system can come from human or animal organic waste or nitrates from fertiliser.

Some 291 areas were monitored for pesticides, but none were detected in private group water schemes last year.

Consumer confidence

Director of the EPA’s office of environmental enforcement Dr Tom Ryan said: “Consumers should be confident that their water is safe to drink.

"Water suppliers are obliged to make sure their water supply is clean and wholesome and is in compliance with the water quality standards.

"It is critical that monitoring is undertaken and, if issues are identified, action must be taken to protect human health.”