A quarter of tanks in Laois and Westmeath were also found to be inadequate.
Half of septic tanks in Offaly and a quarter in Laois and Westmeath failed inspections last year.
A new report from the Environmental Protection Agency raises concerns about delays in fixing faulty tanks, which can affect people's health and the environment.
Just four of the 18 inspections required in Offaly in 2021 were carried out.
The main reasons for the failures include structural defects, and a lack of maintenance.
EPA Inspector Noel Byrne says people need to be responsible for monitoring their own systems:
Mr. Byrne is calling for greater enforcement by local authorities to ensure failed systems are fixed:
All required inspections were in Laois and Westmeath were conducted.
77% of failures in Westmeath were fixed by end of 2021; 75% in Laois; and 73% in Westmeath.
All three counties are regarded as "moderate rate of DWWTS failures fixed".
The figures contained in the 2021 annual report include inspections carried forward from 2020.
Local authorities issue advisory notices requiring householders o fix systems that fail inspection.
Householders should ensure their DWWTS are properly built and maintained and their wells are tested to protect the health of their family. You can get guidance on the EPA website if you are concerned about your DWWTS or well.
DWWTS grants up to €5,000 are available to fix DWWTS in certain circumstances. Details of the eligibility criteria are available on the Department of Housing, Local Government and Heritage website and from the local authorities who administer the grants. Private well grants may also be available for improvement works to private water supplies.
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