Wet weather sewage overflows

Sewerage systems that overflow during heavy rain events are typically caused by excessive, unwanted, and illegal stormwater entering the network. Wet weather overflows can be extreme.

While all efforts are made to prevent overflow or divert it to designated overflow locations, at times, they can occur at maintenance holes located in streets, parks, roads, and – in extreme cases – at properties.

An overflow can put the public health at risk, cause harm to our natural environment and be costly to clean up.

Protecting your property and neighbourhood from a wet weather sewage overflow

Prevent stormwater entering the sewerage network and make sure:

  • your overflow relief gully (ORG) isn't connected to household or landscape pipes
  • your ORG is not at risk of having stormwater enter the network (an ORG is often mistaken for a drain)
  • you don’t have illegal connections to the sewer.

Identifying and managing your overflow relief gully and inspection opening

The ORG and inspection opening (IO) are important points to identify and manage. We recommend knowing where these items are on your property and performing basic activities to allow them to function properly.

ORG identification and management

The ORG looks like a drain but is not a drain. It is designed to protect your property from internal sewage overflows. If there are network blockages or the system surcharges, sewage overflows will be directed out of the ORG and not through the lowest drain in your property. Check that the ORG:

  • grate is loosely fitted and nothing is covering it
  • is 75mm above the surrounding ground level
  • is 150mm below the lowest drain in the property
  • does not allow stormwater, pool water or tap water to enter it. If the ORG does allow these to enter but meets the above requirements, if suitable, it is recommended that a licenced plumber install an ORG Cap. If this cannot occur, system reconfiguration is required to ensure no flow enters the ORG.

Check your pipes diagram(PDF, 156KB)

Learn more about caring for your ORG with the Overflow relief gully fact sheet(PDF, 94KB)

Maintaining your ORG cap

If you have installed an ORG cap, we recommend you regularly check the cap to make sure it is loosely fitted to the ORG. 

The ORG cap must not become ‘stuck’ as the cap is required to pop-up and act as a spill point during any blockage or backflow. You can remove the cap, clean any debris if needed, and put it back in place.

The ORG and its cap are part of the private plumbing, so it is the property owner's responsibility to maintain this fixture and ensure it operates as intended.

If you are preventing stormwater from entering the sewerage network, and you are correctly maintaining the ORG cap, you are decreasing the risks of a sewage overflow occurring in your neighbourhood and property.

IO identification and management

An IO (inspection opening) is a point in the sewerage infrastructure that allows access to your underground sewer pipes for cleaning and repair purposes.

An IO is normally identified by a flat PVC round disk, approximately 180 millimetres in diameter. There may be several, or none, located on your property.

An IO should be capped and not allow any stormwater to enter the network.

If you are unable to locate any IOs, or have an older property with no IO, you should lodge a search request form for sewerage infrastructure drawings for the location of your sewer connections. Find the form on the Preventing & managing sewage blockage, poor drainage & spills page.

Other ways to prevent wet weather overflow

Sewer overflows occur when stormwater runoffs from lawns, roads, roofs and natural ground surfaces flow through incorrect stormwater connections.

If stormwater goes into the wrong pipes, sewerage can back up and cause overflows.

Detect and fix any points on your property where stormwater may enter the sewer. Check that all stormwater flows to a rainwater tank, the road kerb or stormwater pit.

If your street is higher than your house, you may not have a gated stormwater pit in your background. Stormwater may be plumbed directly to the underground stormwater system.

If you think your stormwater pipes are connected to the sewerage system, have them inspected and fixed by a licensed plumber.

Check where your swimming pool discharge flows. During rain events, divert pool backwash water to the sewer and overflow water to the stormwater system.

Learn more: Protect your home against wet weather sewage overflows fact sheet(PDF, 286KB)

Inflow Mitigation Program

The City’s Inflow Mitigation Program, was aimed at improving the level of compliance of private sewerage plumbing, reducing excessive stormwater inflow, and mitigating wet weather sewage overflows. It ran from 2020 to 2023.

Approximately 4500 properties were inspected across Helensvale, Nerang, Elanora, Currumbin Waters, Mudgeeraba, Southport, Hope Island, Coomera, Benowa, Worongary, Oxenford and Robina. The results found that 16% of properties have issues with stormwater entering the City’s sewerage network.

In collaboration with property owners, we have seen 65% of issues resolved. Following this voluntary compliance phase, the City may implement an enforcement phase to achieve the highest possible level of compliance.

It is essential as a property owner you understand your responsibility to prevent sewage overflows.

The most common issues identified were:

  • defective/low-lying overflow relief gullies (ORG)
  • inspection openings (IO) with defective/missing lids
  • incorrect stormwater connections to the sewerage network.