Offaly had the highest failure rate of the three counties.
More than half of septic tanks inspected last year did not meet environmental standards.
The tests were carried out by local authorities across the country, on behalf of the Environmental Protection Agency.
There was a 51 per cent failure rate, and 26 per cent were found to be a risk to human health or the environment.
61 inspections were carried out in the midlands last year - with a 56 per cent failure rate in Offaly, 29 per cent in Laois, and 16 per cent in Westmeath.
EPA inspector Noel Byrne says bad septic tanks can be very dangerous:
He says there are a number of reasons why tanks fail:
Gardaí Searching For Missing Midlands Man
Cabinet To Sign Off On Overhaul For Rural And Gaeltacht Housing
Venezuela Earthquake Death Toll Expected To Reach 10,000
Three Laois Men Fined Thousands After Illegal Removal Of Native Hedgerow
All Aboard! Electric Picnic Reveals Salty Dog Lineup
Westmeath Council Introduces New Rent Rules For Carers
Fuel Excise Cuts Extended Until September
Man Arrested In Laois Pleads Guilty Of Terrorist Plot On Galway Mosque
Teenager Dies Following Carlow Crash Overnight
Tributes Pouring In For Westmeath Malaga Victims
Enterprise Minister Defends Higher Hotel VAT Rate
Laois Man Crash Victim To Be Laid To Rest Tomorrow
Laois Council Seeks Inclusion In 'Living City' Initiative
Westmeath Man Named Supreme Milk Quality Champion
Offaly Councillor Sees "Great Potential" For Village
Legislation Providing Paid Leave For Early Pregnancy Loss To Go To Cabinet
Offaly Councillor Seeks More Roads Funding In North Of County
Revenue Seize Contraband Worth Over €153k
Plans Lodged For New 24-Hour Automated Car Wash in Laois
Westmeath School Joins Expanded Online Admissions System