Wastewater systems

How we process water when you're done with it

Wastewater, also known as sewage, is the used water that goes down sinks, toilets and drains all over Greater Sydney. We keep it moving while protecting the health of our customers and minimising the impact on the environment. To do this, we collect and process wastewater through a complex, coordinated combination of carefully monitored facilities and a network of pipes.

To see where our operating wastewater systems are located, take a look at our wastewater systems map.

Our wastewater systems

We have 24 separate systems that are licensed by the NSW Environment Protection Authority (EPA). They consist of:

How we maintain our wastewater systems

We continually inspect and repair all parts of our systems to fix leaks, remove blockages, maintain equipment and improve treatment processes. We continue to look for ways to better protect public health and the environment as we prepare for a growing city and work towards a circular economy.

We aim to:

  • use technology better to find and fix problems – hopefully, before they occur
  • reduce leaks and blockages
  • improve treatment processes
  • reduce odours and other impacts on our customers
  • increase water recycling
  • increase recovery of resources such as water, energy, nutrients and organic matter from wastewater.

Find out more about how we're improving our wastewater systems.

Who owns wastewater pipes

We own and operate the wastewater network for Sydney, the Illawarra and the Blue Mountains, which services around 5,271,000 customers. We're responsible for nearly 27,000 kilometres of wastewater pipes. Customers own about another 20,000 kilometres of wastewater pipes. These are on customers' private properties. Most of the wastewater in the network flows by gravity along natural catchment drainage lines to a water resource recovery facility.

Types of wastewater sewerage systems

The most common types of wastewater sewerage systems are gravity, pressure and vacuum. To understand the maintenance responsibilities for each of these, have a look at the diagrams of typical water and wastewater connections.

How we treat wastewater

When wastewater arrives at a water resource recovery facility, we use different processes to remove impurities and recover valuable resources. Treated wastewater is either recycled or discharged to waterways.

The wastewater solids we capture during treatment are stabilised to produce nutrient-rich material called biosolids. These are used in agriculture, horticulture and mining. In some cases, we also produce biogas during the stabilisation process. We use biogas to produce heat and renewable electricity. We send other waste materials that can't be recycled to landfill.

Find out more about the levels of wastewater treatment and our water resource recovery facilities.

Why we monitor wastewater

Wastewater collected from homes and businesses all over Sydney contains:

  • nutrients
  • organic matter
  • bacteria
  • cleaning products like shampoo and detergents
  • trade waste from commercial and industrial customers.

If left untreated, this water would harm our environment and the animals that live in it. To protect the environment, we treat wastewater to a level set by the NSW Environment Protection Agency (EPA).

We continually monitor our environmental performance. We check how we impact the rivers, harbours and beaches across our entire area of operation. We manage our systems to make sure we minimise impacts on our waterways so they’re safe for:

  • swimming
  • boating
  • fishing
  • animals
  • irrigation.

We routinely check what's in the wastewater after it's treated. We report this in our EPA pollution monitoring data reports. We also publish yearly reports on our Sewage Treatment System Impact Monitoring Program.

Learn more about the safety of Greater Sydney’s harbour and ocean beaches. Visit the NSW Office of Environment and Heritage's Beachwatch Program.

Stay safe when working with wastewater
If you're a plumber and concerned about working in and around wastewater, read our Chemwatch Safety Data Sheet (514KB). This explains what substances can be found in wastewater and how you can minimise the risks.

Environment protection licences

The NSW Environment Protection Authority (EPA) has issued environmental protection licences for all our wastewater systems. It reviews these licences every 5 years. 

We test water quality at our water resource recovery facilities, water filtration plants and the advanced water treatment plant every month. We continue to work with the EPA to improve the licences and consider any long-term issues. You can find out more about our position on current and future EPL developments (57KB).

We place a high priority on protecting the environment and ensuring our operations minimise impacts on the environment and the community. Your feedback is welcome at any time.

We keep a register of information for each licensed treatment system that includes:

  • maps showing the relevant infrastructure
  • the catchments, sub-catchments and sensitive areas in the wastewater system
  • a schedule of proposed and completed works
  • complaints about overflows.

You can view these registers at our Parramatta head office. Call us on 13 20 92 to arrange an appointment.

Sewer mining

To help secure Sydney’s water supply for the growing population, wastewater can be extracted from a local wastewater system and treated to produce recycled water. This is known as sewer mining. The wastewater is treated on-site using a small treatment plant. Recycled water produced from sewer mining operations is used:

  • in some commercial buildings and industrial sites for toilet flushing, and cooling towers
  • to irrigate sports fields, parks and golf courses.

To find out more about sewer mining, you can:

Northside Storage Tunnel

The Northside Storage Tunnel helps protect public health, recreational activity and aquatic ecosystems in the Sydney Harbour catchment. It stores wastewater and stormwater that would otherwise have overflowed into the Sydney Harbour during heavy rain.

Find out more about how the Northside Storage Tunnel works and where it's located.