An overflow relief gully (ORG) is a grated outlet located in the ground outside your home, usually near the laundry. It's designed to act as a release valve in the event of a blockage or if there's excess rainwater in the sewerage network. It forms a critical part of your household plumbing and helps prevent sewage from flooding your house by directing the overflow outside. 

If a sewer blockage occurs, or the sewerage network can’t cope with rainwater during a storm, the ORG fitting should pop off to release the pressure and direct the sewage away from your home.


Preventing stormwater from entering the sewerage network helps reduce sewer overflows.

  • If your ORG is set too low or your property is in a low-lying area, it can flood and contribute to stormwater entering the sewer system.
  • Improper stormwater connections from downpipes or water tanks being connected to ORGs or sewer pipes can also contribute to stormwater inflows.

Overflow relief gully

Plumbing regulations require ORGs to be installed: 
  1. So they sit at least 150mm lower than the lowest internal household drain. Because they are the lowest point, any sewage that can’t go down the sewers will flow out of this point rather than backing up in your household pipes and overflowing inside. 
  2. At least 75mm above ground level to avoid collecting stormwater during heavy rain.
An ORG should only be altered or installed by a licensed plumber.
  • Properties built before 1976 may not have had an overflow relief gully installed unless some renovation work or improvements have been carried out.  
  • Some older houses may have a disconnector gully or vent. If you have one of these we recommend you contact a licensed plumber who can easily convert them to an overflow relief gully.
  • If you can't locate your ORG, we also recommend contacting a licensed plumber. It may have been covered by landscaping or concrete and this could lead to plumbing issues in the future.
The property owner should keep the ORG and all other plumbing and drainage in good condition and operating correctly.
  • Check your ORG is not covered by landscaping, garden beds, pot plants or other items.
  • Regularly check that the metal or plastic grill covering the ORG is loosely fitted and can easily pop off to allow any overflow to occur.
  • Make sure any overflows are directed away from the house and can drain away quickly.
  • Check stormwater in your yard drains away and does not build up or flood your ORG.
  • Do not direct stormwater and run-off from down pipes and water tanks towards the ORG.
An ORG cap can be fitted to increase the height of your ORG and prevent stormwater from flooding it, which can overload the sewerage system and lead to overflows. If the ORG needs to release built-up pressure from your plumbing, the cap will automatically lift. It's important as part of your home maintenance routine to check the cap is not covered, remains properly seated and can easily lift off in the event of an overflow.

It is the property owner’s responsibility to make sure the ORG is properly fitted and maintained. A non-compliant ORG may impact on insurance claims for damages resulting from a sewer spill. Note: houses with multiple bathrooms may have more than one ORG.

Read more about who is responsible for the plumbing and infrastructure in and around your home.

ORG cap installation service

Urban Utilities provides a free ORG cap installation service to customers

Request ORG cap installation

ORG cap installation FAQs

Yes, but once installed, the ORG cap will become part of the private plumbing on your property and therefore will be your responsibility to maintain.
ORG caps are installed by third party licensed plumbers. If you request an ORG cap installation, please be aware that you are agreeing that Urban Utilities may provide your contact details to a licensed plumber who will undertake the ORG cap installation.

Example of an installed ORG cap

org cap