Search for a licence or permit

Waste water

Waste water from our homes includes water from toilets, sinks, bathrooms, dishwaters and washing machines. The objective of waste water treatment is to remove polluting material so that the treated water can be released safely back into the environment. Depending on where you live, your waste water either goes to a public sewer (also known as urban waste water treatment plants) operated by Uisce Éireann, or your own domestic waste water treatment system.

house with lake and forest

Code of Practice for Domestic Waste Water Treatment Systems

The new 2021 Code of Practice applies from 7th of June 2021. The 2009 Code of Practice may still be used where planning permission has been applied for or site assessment commenced before the 7th June 2021

Inishboffin water supply

National Inspection Plan

The Environmental Protection Agency is responsible for the development of the national inspection plan for domestic wastewater treatment systems.

Decorative Icon above link to licences and permits or My Local Environment

Search your local area

My local environment

Take action on septic tanks

Operating and maintaining septic tank systems Domestic Waste Water Treatment System Inspections 2023
Learn about urban waste water

Domestic waste water

Domestic waste water treatment systems (DWWTS) are used by householders to treat sewage. There are nearly half a million systems in Ireland, mostly septic tanks. DWWTS can contaminate household wells with harmful bacteria and viruses if not built and operated properly. Excessive releases of nutrients such as nitrogen and phosphorus can cause pollution in rivers, lakes and coastal waters.

What's happening?

Septic tank infographic - how a tank treats water

Septic tank and other domestic waste water treatment systems

‘A well-maintained septic tank system will protect your health, your environment, and your pocket’

Septic tanks and other domestic waste water treatment systems are used by rural homeowners to treat waste water from their homes. There are nearly half a million of these systems in Ireland. The majority are septic tank systems, with some more complex filter systems and mechanical treatment plants.

How does a septic tank system work?

What are the health and environmental risks?

What can you do if you are concerned?

Who does what?

View the report on the Domestic Waste Water Treatment Systems Inspections 2023

Code of practice for new builds

Planning applications for new houses must show that the site is suitable for the proposed septic tank system and meets the requirements in:

Code of Practice for Domestic Waste Water Treatment Systems (Population Equivalent ≤ 10)

Standard Recommendation (S.R) 66 and the associated EN 12566 series of standards

Learn more in the code of practice

What's being done?

Septic tank inspections

The national inspection system started in 2013. Its purpose is to protect human health and environment from the risks from septic tank systems. Local authorities inspect over 1,000 systems each year.

Inspections of septic tanks and other domestic waste water treatment systems are done by City and County Council staff. They complete a specific training course and are appointed by the EPA. They carry a certificate of appointment and identification which they will show to the homeowner if requested.

What to expect from an inspection

Planning and reporting inspections

Repairing and replacing faulty septic tank systems

Septic tank inspections show that typically half fail with a quarter being a risk to human health or the environment. Many issues can be addressed through simple maintenance and de-sludging. However, in other cases septic tank systems have serious structural problems that require repair or replacement.

Septic tank systems requiring repair or replacement may be identified by City and County Councils through inspections under the National Inspection Plan, River Basin Management Plan work or in investigating complaints. In all these instances, the homeowner will be made aware of the issues by the Council. However, many homeowners will be aware of issues and want to deal with them on their own initiative to ensure they protect the health of their family, the environment and comply with legal requirements.

What are the problem signs?

Who to contact?

Guidance & Grants

What standards do I need to meet?

What if I am concerned about my neighbour’s septic tank system?

What should I do if my septic tank system is flooded?

FAQs about domestic waste water

in: Waste water

Wastewater FAQ's

  • What is the modified test method? When is it to be used?

    The modified percolation test may be used to obtain a percolation test result in areas with low permeability soils. The modified percolation test may be used where the initial drop T100 >210 minutes using the standard percolation test method or where it is determined by trial hole assessment that the subsoil is CLAY or SILT/CLAY and the percolation value is likely to be greater than 50.

  • What can I do if I have a high water table?

    The water table is the level of groundwater in the soil. Much of the treatment of the liquid effluent from septic tank systems takes place naturally in the soil, so the soil needs to be deep enough for this to happen before the liquid gets to the groundwater. A ‘high water table’ is one that is near the surface. This is checked during site suitability assessment by digging a hole with a digger. If the water table is high, there are some types of systems that are raised and/or do not require deep unsaturated soils.  Consult the Code of Practice for more details or seek advice from a qualified person.

  • How far must the septic tank system be from wells, rivers, neighbours etc.

    These requirements are set out in tables  6.2 and E2 in the Code of Practice.

    For septic tank systems and wells, the minimum requirement varies from 15-60m depending on whether the well is up, across or downgradient, the percolation value, soil type and depth.

  • How can I apply for the site suitability assessment training course?

    This course is run by the Water Services Training Group which is part of the Local Authority Services National Training Group.

  • Who can carry out site suitability assessments and install septic tank systems?

    The Code of Practice and Building Regulations guidance require that site assessment and the design, installation and commissioning of septic tank systems should be carried out and/or supervised by a suitably qualified person or persons. Specific qualifying criteria are not specified and there are no registration requirements, so it is not possible to provide a list.

Featured reports on domestic Waste water

in: waste water
house with lake and forest
Domestic Waste Water Treatment System Inspections 2023

Domestic Waste Water Treatment System Inspections 2023

Read the key findings on the inspections carried out in 2023.

cover page of 2021 Code of Practice
Code of Practice for Domestic Waste Water Treatment Systems

The 2021 Code of Practice for Domestic Waste Water Treatment Systems (Population Equivalent ≤ 10) provides guidance on the site characterization, design, operation and maintenance of domestic waste water treatment systems.

Thumbnail for septic tank leaflet
Have you completed a septic tank system check?

Find out what you need to check to ensure your septic tank system is constructed and maintained properly.

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

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

thumbnail for Septic Tanks & Wastewater Systems when buying or selling a house
Septic Tanks & Wastewater Systems when buying or selling a house

What you need to consider about the septic tank or wastewater system

Watch our videos on Waste water

Download infographics and factsheets on Domestic Waste Water

Infographic on septic tank systems

Domestic Waste Water charts and graphs

Download charts & graphs
graph DWWTS failures open more than 2 years 2023
DWWTS failures open more than two years

DWWTS failures open more than two years at the end of each year 2016 to 2023

Graph reasons for DWWTS failures 2023
Reasons for DWWTS failures 2023

Individual DWWTS can fail inspections for multiple reasons.