Domestic Wastewater Treatment Systems (DWWT's)

Over one-third of the population of Ireland lives in rural areas (CSO, 2017). Much of the waste water from such rural settlement patterns is disposed of to domestic waste water treatment systems (DWWTSs) of various types designed to treat the waste water on site.

Domestic waste water treatment systems are designed to discharge treated effluent to waters, generally in Ireland to groundwater via percolation through the soil and / or subsoil. The conservation and enhancement of the environment is a key objective for the future. It is vital that DWWTS's are installed and operated correctly to ensure the protection of both human health and the environment.


Domestic waste water treatment systems are designed to:

  • treat the waste water to minimise contamination of soils, subsoils and water bodies;
  • prevent direct discharge of untreated or partially treated waste water to groundwater or surface water;
  • protect humans from contact with waste water;
  • keep animals, insects and vermin from contact with waste water;
  • minimise the generation of foul odours.


Public health and water quality are threatened when DWWTS's fail to operate satisfactorily. System failures can result in waste water ponding or forming stagnant pools on the ground when the waste water is not absorbed by the soil and / or subsoil. In such circumstances, humans can be exposed to microbial pathogens and foul odours can be generated. Inadequately treated waste water that emits to the environment because of poor location, design and / or construction may lead to contamination of groundwater and surface waters, which in many areas are also used as drinking water supplies. EPA Code Of Practice: Domestic Waste Water Treatment Systems (Population Equivalent ≤ 10) 2021. More information can be obtained here:

National Inspection Plan

Louth County Council carries out a number of inspections annually in accordance with the Environment Protection Agency’s National Inspection Plan. For further information please see

Registration of DWWTS/ Septic Tanks

If you have a septic tank or similar treatment system, you must register its details with your local authority and pay a registration fee. Households connected to domestic wastewater treatment systems are required to register their systems in line with the Domestic Waste Water Treatment Systems (Registration) Regulations 2012  (SI No. 220 of 2012), as amended by Domestic Waste Water Treatment Systems (Registration)(Amendment) Regulations 2013  (SI No. 180 of 2013)

The general deadline for registration was 1 February 2013, but late registrations are still being accepted - see below. If you register after the deadline, you will not be eligible for any grant if your system is found to need remedial work - see ‘Grant Information' below.

New systems which have been installed or built after 1 February 2013 must be registered within 90 days of being connected. Replacements of previously registered systems do not have to be registered separately

You can register your system:

  • Online at
  • By post: You can download a form (pdf). Forms are also available by calling LoCall 1890 800 800 for information. Cheques should be made payable to ‘Protect Our Water’ and posted to Protect our Water, PO Box 12204, Dublin 7.