Almost six out of every ten septic tanks inspected across Ireland last year failed, putting drinking water, wells and rivers at risk, the Environmental Protection Agency has warned. The numbers in Donegal are even higher according to recent statistics from Donegal County Council, placing failure at nearly 70 percent.
Of 1,466 inspections carried out nationally by local authorities in 2025, 863 – or 59% – failed, with a significant number posing a risk to human health and the environment.
Donegal has been singled out alongside Fingal and Wexford as one of three local authorities that failed to meet its annual inspection quota, and will now be required to double its inspections this year to make up the shortfall.
Faulty tanks can contaminate drinking water wells with harmful bacteria and viruses, while illegal discharges to ditches and streams, leaks, ponding and inadequate desludging are among the most common causes of failure. Excessive nitrogen and phosphorus releases have been linked to pollution in 148 water bodies nationwide.
On a more positive note, 84% of tanks that failed inspection were fixed by the end of 2025. The availability of an enhanced government remediation grant – increased from €5,000 to €12,000 in 2024 – has been credited with driving that improvement.
There are nearly half a million domestic wastewater treatment systems in Ireland, used in homes not connected to the public sewage network. Nationally, local authorities are required to carry out a minimum of 1,200 inspections annually, generally targeting areas near at-risk rivers and where septic tanks are located close to household drinking water wells.
The EPA has called for more consistent enforcement across all local authorities to ensure faulty systems are repaired promptly and that public health and the environment are protected.