overfow relief gullyA properly functioning overflow relief gully is critical infrastructure in your homes sewer house drains. The overflow relief gully (ORG) is installed outside your home for your protection to prevent sewage overflowing and flooding inside your house.

Very simply it is a grated outlet connected directly to your sewer house drain. It’s sole purpose, which is critical to you, is for the grate to pop off if there is a sewer blockage and let overflowing raw sewage overflow onto your gardens rather than inside your home.

An overflow relief gully in a garden is illustrated in the photo on the right. They are generally located outside the laundry or kitchen either in the garden or concrete path.

How Does An Overflow Relief Gully Work?

A correctly installed and maintained overflow relief gully will always act as an emergency release point whenever a sewage blockage occurs.

The overflow relief gully by law is required to be 150mm lower than the lowest drain connection inside your house. Because it is the lowest open sewer drain connection on your property any overflowing sewage will automatically flow outside as can be seen in the photo on the left.

If your sewer house drain blocks and sewage flows cannot flow into the council sewers the sewage flow will backup in your drains. This backup will make the loose fitting black grate pop off completely. Once the grate pops the sewage will flow freely onto your garden and lawn area rather than inside your home.

Cleaning up a sewage overflow outside your home is much easier and far less stressful than cleaning up sewage overflowing into your home and damaging floors and furniture.

Maintaining Your Overflow Relief Gully

It is your responsibility as a property owner to maintain your entire sewer house drain in a good operating condition. The overflow relief gully is a critical part of the sewer drain infrastructure and it must be properly installed and maintained. An illegal or non-compliant overflow relief gully has the potential to null and void insurance claim damages in the event of a sewage overflow.

You must make sure that your overflow relief gully is not:

  • covered in any way with pot plants or containers that prevent it working in an emergency
  • covered over when landscaping with paths or gardens
  • the grate unable to pop off due to corrosion or filled with silt, debris, stones or concrete
  • is installed so low  that rainwater can overflow into the sewer drains
  • is connected to roof storm-water down-pipes

You must always make sure that your overflow relief gully has:

  • a loosely fitted metal or plastic grill that will easily pop off completely to allow sewage to overflow in an emergency
  • a clear drainage area so that any overflowing sewage flows away from your house and does not build up around the overflow relief gully
  • is correctly installed 100mm above a grass or garden area or 50mm in a concrete path or paved path


Schedule a site inspection today if you have any concerns about the condition of your overflow relief gully or call us now (07) 5580 4311