National Inspection Plan 2018-2021: Domestic Waste Water Treatment Systems

This report outlines the proposed third national inspection plan for domestic waste water treatment systems (DWWTS) for the period 2018 to 2021.

The Water Services Act 2007, as amended by the Water Services (Amendment) Act 2012 requires the EPA to prepare a national inspection plan for DWWTS. The purpose of the plan is to protect human health and water quality from the risks posed by DWWTS (also known as septic tank systems).

The EPA prepared the first national inspection plan for DWWTS in 2013 covering the period 2013 to 2014. The plan required local authorities to undertake a minimum of 1,000 inspections each year across the country. The EPA developed a risk based methodology to assist the local authorities with the selection of locations for inspections. The methodology took into account the potential risks that DWWTS pose to both human health and water quality.

The second national inspection plan for DWWTS in 2015 outlined the inspection process covering the period 2015 to 2017. Some minor changes were made to the risk maps used for site selection as additional environmental data had become available. This also resulted in a slight change to the number of inspections in some counties.

This third plan has been prepared for the years 2018 to 2021. The risk-based methodology has been updated to take into account additional information gathered on water quality during the preparation of the River Basin Management Plan 2018 – 2021. Further information on the revised methodology is provided in section 2 of this report.

The minimum number of inspections across the country remains at a 1,000 inspections per annum. However, the minimum number of inspections required in each local authority area has changed in response to the revised methodology and further details are provided in section 3 of this report. The final number of inspections remains a matter for each local authority. Additional inspections should be carried out where evidence exists that DWWTS are causing an issue in a particular catchment.

Under the national inspection plan local authority inspectors are required to undertake a minimum number of inspections each year. Any shortfall in the number of inspections completed at the end of the 2015 to 2017 reporting period will be carried over and added to the number of inspections to be undertaken in 2018.

Close to half of all inspection failures have been related to the operation, maintenance and desludging of DWWTS.

Private wells may be at risk of contamination if the DWWTS are not sited, installed or operated correctly (in 2016, it was found that 51% of DWWTS, with private wells on site, failed inspection).


Local authorities must maintain a register of all complaints and other inspections, such as water pollution incident investigations, that relate to DWWTS. But this file is not in the public domain

Likelihood of Inadequate Percolation

Potential risk to groundwater supplies from DWWTS

National inspection plan 10 risk zones map

Minimum number of inspections by county

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