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Domestic Wastewater Treatment Systems (Septic Tanks)



Domestic Wastewater - General Information on Septic Tanks

Wastewaters from single houses in the countryside, that are not connected to sewers, are generally treated on-site by septic tank systems or secondary treatment systems, which come under domestic wastewater treatment systems, (DWWTS).


How a septic tank treats your wastewater



DWWTS accept sewage and waste water from toilets, and what is termed grey water from showers, sinks, wash hand basins, washing machines and dishwashers. The greater the population of the dwelling, the greater the volume of waste water produced. A DWWTS is assumed to have a daily hydraulic loading for each person of 150 litres and typical household occupancy of 2.8 people. 

There are a number of different pollutants in domestic waste water and on-site DWWTS can threaten public health and water quality when they fail to operate satisfactorily. When the wastewater is not absorbed by the soil it can form stagnant pools on the ground surface or discharge into water-courses. In such failures, humans and animals can come in contact with the wastewater and be exposed to pathogens, e.g. faecal coliforms and E. coli. A malfunctioning system can also contaminate groundwater and private wells, while foul odours can also be generated.

The EPA website provides an Animation on how a DWWTS (septic tank or treatment system) works.


Advice on installing & maintaining a DWWTS

The Environmental Protection Agency (EPA) has published excellent guidance in the form of the Code of Practice for Domestic Waste Water Treatment Systems


This describes how a suitable treatment system should be designed, installed and maintained, including advice on infiltration (percolation) areas of various kinds depending on ground conditions.


Key Points to Note

  • All grey water discharges from the dwelling house, (sinks, showers, baths, washing machine, dishwasher), should be connected to the DWWTS (septic tank).
  • Roof water and surface water from gullies around the dwelling should not be connected to the DWWTS, but should be piped to the nearest water-course. (This avoids hydraulic overloading of the DWWTS and ensures that clean water stays clean)
  • Homeowners are responsible under the Water Services Act (as amended) for regular inspection & maintenance of their DWWTS, and failure to do so may lead to substantial replacement costs.
  • DWWTS will not function indefinitely without being de-sludged, ideally on a regular basis by a permitted contractor, (see list of permit holders below.
  • Homeowners should carry out periodic checks as described in the EPA guidance,


 Septic tank system check


Registration & Legislation


  • A registration system for DWWTS is in operation, with most existing DWWTS registered before the 1st February 2013, in accordance with the Water Services (Amendment) Act 2012 and S.I. No. 180 of 2013 - Domestic Waste Water Treatment Systems (Registration) (Amendment) Regulations 2013.
  • If you have not registered, you should still do so on Protect Our Water website. The website also provides a comprehensive FAQ section.
  • All new development, where a DWWTS is constructed or installed, shall ensure that the system is registered with the local authority within 90 days of connection of the premises to DWWTS ( S.I. 180 of 2013).
  • It is an offence not to register your system, (new or existing).
  • Regulations governing the operation and maintenance of domestic wastewater treatment systems (DWWTS’s) ( S.I. No. 223 of 2012) require owners of DWWTS to operate and maintain their systems so as not to pose a threat to the public or to the wider environment.


Further Information on the legislation  is given on the EPA Website.


Further Information on Registration:


The above information is also available in Irish at


Septic Tank Inspections

National Inspection Plan for Domestic Waste Water Treatment Systems 2022 - 2026


The Environmental Protection Agency has published the National Inspection Plan for Domestic Waste Water Treatment Systems 2022 - 2026: Domestic Waste Water Treatment Systems (NIP), which aims to protect water and human health from the risks posed by domestic waste water treatment systems. Since the plan was first developed in 2013, it has recommended a two strand approach of (i) public engagement (advice & communication) and (ii) risk based inspections.


The Plan requires a minimum of 1,000 inspections per year, of which Donegal Co. Council has been allocated a minimum of 118 inspections annually. The plan allocates inspections to various areas or risk zones and Donegal Co. Council then selects geographical areas based on risk to sensitive receptors, such as drinking water abstraction sources, pearl mussel catchments, high status objective catchments, bathing water catchments etc.


The EPA reports annually on the implementation of the NIP and general findings from local authority inspections, such as common causes for failures. The most recent report can be found at



Preparation for an Inspection


Homeowners will be notified at least 10 days in advance of an upcoming septic tank inspection under the NIP. They will be provided with information on;


  1. The format of the inspection, detailed in the information leaflet What to expect from an Inspection
  2. Advice on desludging, including a list of permitted contractors, DCC Desludging & WCP Contractors Nov 22
  3. General information on septic tanks, in the following leaflets


Information leaflets
What you need to know about your septic tank
Is your well at risk from your septic tank
What to expect from your septic tank inspection

What to Expect



There are certain things you can do to make sure that your DWWTS (septic tank or treatment system) is working properly - See what you can do.



Failing an Inspection


If you fail an inspection under the NIP (Water Services (Amendment) Act 2012), you will have to take steps to repair or remediate your DWWTS so that it does not cause a risk to human health or the environment.  Donegal Co. Council will issue an Inspection Report, detailing the findings of the inspection, and an Advisory Notice listing the remedial steps required to be undertaken within a fixed period of time. Homeowners may apply for an extension of time, which may be granted in certain circumstances, but failure to engage and complete remedial actions in an Advisory Notice is an offence and prosecutions have been taken under the relevant legislation.


The EPA provides comprehensive advice on how remedial works should be undertaken so as to fully comply with all relevant legislation, including Planning requirements in Advice notes on remediation and replacement of DWWTS.



Additional Information


DWWTS Sludge


The EPA provides Information for farmers who want to spread sludge from their own septic tanks or wastewater treatment systems on their own agricultural land, in accordance with S.I. No. 148/1998 - Waste Management (Use of Sewage Sludge in Agriculture) Regulations, 1998,  in the guidance leaflet shown, available on their website.


Please note that this does not permit a farmer to spread sludge for anyone else’s septic tank, nor to transport such material.


Septic Tank Inspection Findings


Septic Tank Inspection Findings


 Septic Tank inspection findings


Wastewater Systems for building a house

The EPA has published guidance documenting what you need to consider if you are planning to install a septic tank or wastewater system for a domestic dwelling, and how to apply to your local authority for planning permission.


Please note that homeowners will not be eligible for any grant aid for properties under 7 years old.


Septic Tanks & Wastewater Systems when buying or selling a house

The EPA has also published guidance documenting what you need to consider if you are planning to buy or sell a house that has a private wastewater system (including a septic tank) installed on the site. The checklist in this leaflet will help you to find out what you need to know about the system, which will help to ensure the system is efficient, safe and complies with local planning policies and regulations.


Failure to properly assess a DWWTS can leave you with costly & unplanned remedial works.


The above information is also available in Irish at



Information on Grants

On the 4th November 2023, Minister Darragh O’Brien Department of Housing, Local Government & Heritage issued a press release (available at announcing changes to the septic tank grant schemes, increasing the maximum grant from €5,000  to €12,000 and removing the requirement for homeowners to have registered their DWWTS with Protect Our Water on or before 1st February 2013. These changes came into effect on the 1st January 2024. In order to qualify for the grant, the house served by the DWWTS must, in the opinion of the local authority:


a)     be occupied by the applicant as their primary place of residence (e.g. not a holiday home or rental property),

b)     not be connected to a public sewerage scheme, (but can connect to one)

c)     not be currently under construction or constructed within the last 7 years,

d)     not have been paid a grant for the DWWTS within the last 7 years, and

e)     have all works completed satisfactorily in accordance with an Advisory Notice.


1. National Inspection Plan: Grants are available to fix septic tank systems that were selected for an inspection by a Local Authority under the National Inspection Plan (NIP) and were deemed to have failed. The homeowner will receive an Advisory Notice from the Local Authority indicating what elements of the system requiring remediation, repair, upgrading or replacement. The Local Authority will also handle the grant application submitted after works are completed.

2. Priority Areas for Action (PAA’s): Grants are available to fix septic tank systems in these areas that are or may be causing a threat to the environment and need remediation, repair, upgrading or replacement. These systems will be identified by the Local Authority Waters Programme Office (LAWPRO) who will issue a letter confirming eligibility to apply. The homeowner can then apply to the Local Authority for the grant.

3. High Status Objective Catchment Areas: Grants are available to fix septic tank systems in these areas that are or may be causing a threat to the environment and need remediation, repair, upgrading or replacement.


            You can check if you are in these areas by inputting your EIRCODE in a map and apply to Donegal Co. Council for the grant. If located in a green area, the homeowner should contact the local authority to organise a confirmatory inspection.



 High Status Catchment area map



The High Status Objective Catchment Area map is available in Irish via the following link :


Note:  Location of a property in a PAA is no guarantee of eligibility for a grant under this scheme.


All eligible works to DWWTS for the purpose of obtaining one of these grants must be carried out in accordance with the EPA 2021 Code of Practice for Domestic Waste Water Treatment Systems.

Important: Costs incurred for the routine maintenance, servicing or de-sludging of a DWWTS do not qualify for a grant.




S.I. No. 562 of 2023 – amendment of the original grant scheme (NIP)

S.I. No. 563 of 2023.  – applies to PAA’s

S.I. No. 564 of 2023 – applies to High Status Objective Catchments (HSOC)



Application Forms, Terms & Conditions

Details of Terms & Conditions (including the procedure for applying and an application form) for grant aid for eligible works to domestic waste water treatment systems in houses, selected or situated as follows are available from the Department of Housing, Planning and Local Government at the following links:







An application form) for grant aid for eligible works to domestic waste water treatment systems in houses, selected or situated as follows are available from the Department of Housing, Planning and Local Government at the following links:


1. EPA’s National Inspection Plan (NIP) - no application is required and grant may be claimed using Claim Payment Form NIP (a) 2024 or in Irish Claim Payment Form NIP (a) 2024 (ga)‌ after remedial works have been completed & receipts for payment obtained.


2. Prioritised Areas for Action (PAA) - application should be made using Application Form PAA (a) 2024 or in Irish Application Form PAA (a) 2024 (ga) and claims for grant aid made using Claim Payment Form PAA (b) 2024 or in Irish Claim Payment Form PAA (b) 2024 (ga)


3. High Status Objective Catchment Areas (HSOC) - application should be made using Application Form HSOCA (a) 2024 or in Irish Application Form HSOCA (a) 2024 (ga) and claims for grant aid made using Claim Payment Form HSOCA (b) 2024 or in Irish Claim Payment Form HSOCA (b) 2024 (ga)


The above information, application forms and terms & Conditions are available in Irish at:


Grants are administered by Donegal Co. Council; contact the Water & Environment Section if you require further information or wish to enquire about an application, Tel 074-9153900.


Privacy Notice (Department of Housing, Planning & Local Government)

The Department is committed to protecting and respecting your privacy. This Privacy Notice explains how the Department, as the Data Controller, will process the personal data provided to it in respect of the management and administration of these schemes of financial assistance; how that information will be used, and what rights you may exercise in relation to your personal data.

 Privacy Notice - Administration of Schemes of Financial Assistance under the Multi-Annual Rural Water Programme 2019-2021 (259.27 KB)


 Fógra Príobháideachais (An Roinn Tithíochta, Rialtais Áitiúil agus Oidhreachta)

Tá an Roinn tiomanta do do phríobháideachas a chosaint agus a urramú. Mínítear san Fógra Príobháideachais seo an chaoi a bpróiseálfaidh an Roinn, mar an Rialaitheoir Sonraí, na sonraí pearsanta a chuirtear ar fáil di maidir le bainistiú agus riarachán na scéimeanna cúnaimh airgeadais seo; conas a úsáidfear an fhaisnéis sin, agus na cearta is féidir leat a fheidhmiú maidir le do shonraí pearsan

 Fógra Príobháideachais - Scéimeanna cúnaimh airgeadais a riar faoin gClár Uisce Tuaithe Ilbhliantúil 2019 - 2021 (393.45 KB)


Further Information:

DCC Desludging Guide & WCP Contractors Nov 2022

Remediation and Replacement of Domestic Waste Water Treatment Systems


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