Wastewater network

How we handle water when you're done with it

Getting rid of water after it's been used is a big part of what we do. Wastewater is the used water that goes down sinks, toilets and drains all over Greater Sydney. You'd notice if we weren't managing it. 


What's included in our wastewater network

Our wastewater network consists of:


How we maintain our wastewater network

We continually inspect and repair all parts of our wastewater network 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
  • reuse waste products. 

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


Who owns wastewater pipes

We own and operate the wastewater network for Sydney, the Illawarra and the Blue Mountains – servicing over 5,136,000 customers. We're responsible for 26,169 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 wastewater treatment plant.


What types of wastewater systems we manage

The most common types of wastewater connections 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 on our connections page.


How we treat wastewater

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. 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.

Find out more about the levels of wastewater treatment and our wastewater treatment plants.


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

Safety when working with wastewater

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


Who issues Environmental Protection Licences

The NSW Environment Protection Authority (EPA) has issued Environmental Protection Licences (EPLs) for all our wastewater systems. It is currently conducting its 5-yearly review of these licences. 

We test water quality at our wastewater treatment plants, water filtration plants and at the advanced water treatment plant every month. We'll 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. 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.

EPA pollution monitoring data reports

We test water quality at our wastewater treatment plants, water filtration plants and at the advanced water treatment plant every month.


What sewer mining is

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.

Learn more


How we use innovation to monitor our network

Leak detection dogs

We’re reducing leaks in our wastewater (sewer) systems with our new recruits, Winnie and Ziggy, who have a nose for leak detection. Since May 2020, they’ve been sniffing out leaks throughout our wastewater network.

Winnie and Ziggy are trained to alert us to the presence of wastewater (sewage) in our waterways and the environment when there are no other indicators. They can identify wastewater in tiny concentrations, even when we don't realise there's a leak. Once they detect wastewater, they follow their nose and take their handler through the catchment to locate the source. 

No other water utility around the world has trained dogs to detect leaks and odours at levels as low as these dogs can detect.

Creating a better life through innovation

Our dogs embody our innovation program, demonstrating what it means to be a world-class utility that puts protecting the environment and our community’s health first.

Robots in our pipes

Inspecting large sewers (wastewater pipes) is more than just an uncomfortable task. Despite stringent safety requirements, entering sewers is one of the most dangerous tasks in Sydney Water. But it's also essential. We need to inspect the pipes to provide enough information to budget and prioritise repairs and maintenance. This helps us prevent wastewater leaks, blockages and overflows.

Working with partners to keep our staff safe

We’ve been working with IP Pipes, looking for a safer, technology-based solution to inspect these large sewer (wastewater) pipes without sending our teams underground. And now we’ve found a way to check the state of the pipes without entering them. The answer is – the RACER.

RACER – the result of technology crossover 

RACER (Rapid Assessment Condition Evaluation Robot) is the result of recent developments in photogrammetry and sonar technology. It enables us to gather enough information for detailed engineering assessments, without having our employees tramp through the underground network. RACER collects images and sonar data with a special free-floating camera. These are then converted into 360 degree vision and 2D view with sonar data. This allows the operator to view the pipe as if they were inside it themselves, without having to get wet or be at risk.


How the Northside Storage Tunnel fits in

The Northside Storage Tunnel helps protect public health, recreational activity and aquatic ecosystems in the Sydney Harbour catchment. It does this by storing 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.