Just under a thousand (987) inspections were carried out by local authorities under EPA supervision between July 2013 and June last year as part of the first ever national review of domestic waste water treatment systems in Ireland.
Of the 48 percent that failed, the EPA says many could have been avoided by householders taking simple steps to de-sludge and maintain the treatment system.
Following remediation work by householders nearly 8 out ten (79%) of the inspected systems are now compliant with the regulations.
