As many as 290,000 family septic tanks are feared faulty and a health risk to households and their neighbours, an Environmental Protection Agency (EPA) report shows. It warns of “harmful bacteria and viruses” escaping in wastewater from toilets, sinks and household appliances and potentially contaminating drinking water. “People may be exposed to wastewater if it surfaces in gardens or runs off into ditches and streams,” it adds. Of a sample of septic tanks inspected last year, 59 per cent were incorrectly installed, malfunctioning or poorly maintained. The EPA said the failure rate was “worrying” and while the sample size was small – just 1,466 – it was likely quite representative of the almost 500,000 septic tanks in use by homes not connected to mains wastewaters systems. EPA programme manager Noel Byrne said the annual inspections by local authorities were targeted primarily by location – in areas close to waterways and where soils were shallow.There was some scope to focus on older properties where septic tanks might also be ageing but Byrne said: “It’s not overly weighted that way.” “The failure rate has been in or around 50 per cent every year for 13 years so it is broadly reflective of the wider situation.” Of particular concern to the EPA are the 160,000 homes that have both a septic tank and a private well. “You are potentially putting your family at risk here if your septic tank is not working properly because there’s a risk of contaminating the well,” Byrne said. “People will say they get used to their own well water and whatever’s in it but if you have small children, or guests or someone vulnerable, you can really sicken them.” Lack of regular maintenance is a recurring issue, Byrne said. That’s despite the Department of Housing increasing maximum grants for septic tank repair and replacement from €5,000 to €12,000 in 2024. The EPA said this seemed to have reduced the number of homeowners who left failures unresolved for long periods. But there were still 442 cases at the end of 2025 where homeowners had been under notice to address problems for more than two years.That compared with 523 at the end of 2024. The EPA said 88 cases had been escalated to prosecution stage at the end of 2025. “Local authorities need to increase enforcement, including prosecution where warranted,” the EPA said. It added that some local authorities were not fulfilling their annual quota of inspections, with Donegal and Wexford inspecting fewer than required last year. As well as being a risk to public health, human waste and chemicals drives algal growth in streams and rivers, killing other plant, fish and insect life and endangering the animals dependent on them.