Overflows from the wastewater network may occur in wet weather when wastewater flows are increased from illegal connections to the network and because of stormwater infiltration. Wastewater systems are designed to overflow at selected points when necessary to prevent back-up of sewage and reduce the potential for spills within private premises. However, during times of heavy rain, wastewater can discharge through manholes and to private property.
What is wastewater overflow?
When we experience very heavy rain, large volumes of stormwater enter the wastewater network. This can overload the network in severe wet weather events, which increases the chance of an overflow. Download the wastewater overflow fact sheet (PDF 549 KB).
What are common causes of wastewater overflow?
Overflows are largely caused by stormwater entering the wastewater network. Stormwater enters the wastewater network through sources such as illegal roof and property connections, poorly maintained property drains, unsealed manhole lids and leaks in the pipe network due to damage and deterioration. For more information, please view the 'Stopping Wastewater Overflows' video. (see below)
What is an overflow relief gully and what is its purpose?
An overflow relief gully (ORG) is a plumbing fitting located outside your home that is designed to release wastewater in the case of a pipe blockage or network overload. If a pipe blockage or overload occurs, the ORG grate should pop off to release the excess pressure and direct wastewater so it does not enter your home. Download the overflow relief gully fact sheet. (PDF 315 KB)
What are the risks of a wastewater overflow?
Even though wastewater overflows are diluted with stormwater (normal domestic wastewater is approximately 97-99% water), there are some risks to public health if people come into contact with it via hand to mouth contact, skin contact through cuts etc. The dissolved and suspended matter in wastewater can contain many micro-organisms such as viruses, bacteria, fungal and parasitic organisms that may be harmful to humans, animals and the environment, potentially leading to a number of illnesses such as:
- Gastroenteritis (diarrhoea or vomiting)
- Giardiasis and Cryptosporidiosis (severe stomach cramps, diarrhoea or vomiting)
- Viral infections such as hepatitis (liver infections)
- Infections of the skin or eyes
You can reduce your risk of exposure to the above by thoroughly washing your hands, ensuring wounds are properly covered or disinfecting them immediately if you have been in contact with wastewater.
Wastewater can also impact on the water quality of our streams if overflows occur near waterways, or restrict the use of public open spaces until overflows are cleaned up.
What is Council doing to minimise wastewater overflows?
Council manages and maintains the wastewater network to minimise overflows by regularly inspecting and repairing damaged reticulation pipes and manholes; providing emergency storage and controlled overflow points; monitoring the performance of the network; and working towards reducing stormwater ingress to the wastewater network by targeting the source of inflows in the public network and through private plumbing. Inflow and infiltration inspection programs are carried out to identify sources of inflow and infiltration into the network from private properties.
What can I do as a resident to help prevent wastewater overflows?
Residents can reduce the inflow of stormwater into the wastewater network by: checking that their roof water or garden drainage is not directed into the wastewater network through overflow relief gullies; and by replacing faulty and damaged household drainage pipes in their yards. Download Council's Correcting Common Defects fact sheet (PDF 309 KB) for further information about what you can do.
Image sourced: Queensland Urban Utilities