Wastewater network

Wastewater is the used water that goes down sinks, toilets and drains.

Our wastewater network consists of:

We own and operate the wastewater network for Sydney, the Illawarra and the Blue Mountains. This includes 25,085 km of wastewater pipes.

Customers own another 20,000 kilometres of wastewater pipes. These are located on customers' private land.

Most of the wastewater in the network flows by gravity along natural catchment drainage lines to a wastewater treatment plant.

Find out more about types of wastewater systems.
Once wastewater arrives at a treatment plant, we use different processes to remove impurities. We then discharge treated wastewater to waterways.

In some cases, the water is treated again at a water recycling plant.

Find out more about wastewater treatment levels.

We turn the nutrient rich material created from treating wastewater solids into biosolids. These are used in agriculture, horticulture and mining.

We send other waste materials that can't be recycled to landfill.

The NSW Environment Protection Authority (EPA) has issued Environmental Protection Licences (EPLs) for all our wastewater systems. They're currently conducting their five yearly review of these licences. 

We'll continue to work with the EPA to improve the licences and consider any long term issues. Find out more about our position on current and future EPL developments.

We place a high priority on protecting the environment and ensuring our operations minimise impacts on the environment and the community. We welcome your feedback 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.

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 swimming spots in harbours and beaches. Visit the NSW Office of Environment and Heritage's Beachwatch Program.

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 in cooling towers
  • to irrigate sports fields, parks and golf courses.

The number of sewer mining projects is constantly growing. For an up to date list, visit www.waterforlife.nsw.gov.au.

Learn more