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Registering Domestic Wastewater Treatment Systems 

The total number of registered domestic wastewater treatment systems in Ireland in 2021 is 481,694.  There continues to be new registrations of domestic wastewater treatment systems each year. The table below shows the number of new registrations in County Cavan since 2017. 












These new registrations each year are likely to be linked to: 

  • New house builds and the new domestic wastewater treatment system being registered 
  • Existing houses being purchased, and new owners registered their ownership of the property and the associated wastewater treatment system  
  • Existing systems which previously were not registered being registered in line with the requirements of the regulations. 

Domestic wastewater treatment systems include all septic tanks, wastewater tanks, and treatment systems receiving, storing, treating or disposing of domestic wastewater. It also includes all fittings and percolation areas associated with such tanks and systems and drains used to discharge wastewater from a premises, whether or not a receiving tank is present. 

Domestic wastewater treatment systems must be registered in accordance with the Water Services Acts 2007 and 2012 Domestic Waste Water Treatment Systems (Registration) Regulations 2012 (S.I. No. 220 of 2012). The requirement to register is linked to our responsibility to protect ground and surface water quality (particularly drinking water sources) from the risks posed by malfunctioning systems.  Owners of domestic wastewater treatment systems must register as soon as possible after the system is installed.   

All owners of premises connected to domestic wastewater treatment systems must register their system. This includes owners of properties which are let; whether by private landlords or local authorities; and employers who provide living accommodation to employees. All residential premises, including buildings, caravans and mobile homes, or other structures connected to a domestic wastewater treatment system must be registered. 

The registration is managed by Protect Our Water. This is the body responsible for issuing the required Certificate of Registration. 

If you have already registered, you do not need to re-register. The registration fee is set at €50 and your certificate of registration is valid indefinitely.  Email queries may be sent to 

Where an owner is unable to register, for example due to physical or mental incapacity, registration on their behalf should be made by the next-of-kin, legal representative or other authorised or appropriate person. 

On completion of the sale of a property, the purchaser must notify Protect Our Water of the change in ownership of the property and Protect Our Water will update the register of domestic wastewater treatment systems accordingly. 

For further details on registration of your domestic wastewater treatment system, go to

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