The Environmental Protection Agency has reported that more than half of household septic tanks inspected by local authorities have failed their first inspection.
The Agency said that more than 400 inspections have been carried out so far, and that many of the failures could be avoided by households taking simple steps to maintain their treatment systems.
The National Inspection Plan for Domestic Waste Water Treatment Systems has been in operation for eight months and 450,000 septic tanks have been registered by their owners.
To date only 423 of these tanks have been examined, but more than half of them have failed that inspection.
In the majority of cases, the failure was caused because the septic tanks had not been desludged, or they had not been properly operated and maintained.
The Environmental Protection Agency has already appointed 100 local authority inspectors.
It said that the focus to date has been on setting up the inspection regime and providing information to households about how to maintain and rectify simple problems with their treatment systems.
The agency said that these inspections will now become a routine part of local authorities' work.
It also said advice to assist householders is available through local authority leaflets and websites.