The agency recorded an improvement in private household schemes.
Businesses, schools, creches and sports clubs that use a private well need to make sure it's registered.
The EPA's latest report warns that many small private water supplies are not being monitored by the local authority.
Westmeath and Offaly are among ten county councils with 40 or less of these supplies registered.
The agency recorded an improvement in private household schemes - with 14 failing the test for E.coli in 2025, down from 24 the previous year.
Noel Byrne, Programme Manager with EPA, says businesses have a duty to protect their customers:
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