Just under half of the septic tanks inspected by county councils in 2022 failed, and one in five pose a risk to human health, according to new Environmental Protection Agency (EPA) figures.

There were 1,143 inspections carried out of domestic waste water treatment systems and 560 fell short of the required standards.

The failure rate has fluctuated between 44% and 57% since 2013.

The most common issues reported include failure to maintain tanks, failure to desludge and discharges to waterways or ditches.

The EPA stated that there needs to be more enforcement of septic tank and waste water treatment rules by local authorities “including prosecution where warranted”.

Poor enforcement

Roscommon, Waterford, Leitrim and Tipperary were mentioned as counties particularly in need of clamping down on tanks where no remedial works are carried out after faults are found.

Over three quarters of the waste water systems that failed inspection between 2013 and 2022 had been fixed by the end of last year.

Roscommon had the lowest percentage of faulty systems fixed by the end of 2022 at 53%, while Cork, Fingal and Louth all reported correction rates of 100%.

Grants of up to €5,000 are available to fix some defects in tanks

Local authorities in Clare, Offaly, Monaghan and Galway City Council did not complete the number of tank inspections they were required to in 2022 and they are required to make up for this shortfall in 2023’s figures.

Failure rate

“Faulty septic tanks are a risk to human health and the environment,” the EPA’s head of environmental enforcement Dr Tom Ryan said.

“If not built and operated properly, they can pollute watercourses and contaminate household drinking water wells with harmful bacteria and viruses.

“Where septic tanks are not functioning properly, it is critical that householders fix the problems to protect their family’s health, and the environment.”