Our sewerage system is vital to Melbourne’s health, safely transporting sewage to our treatment plants for processing. Find out what happens when you flush the toilet or use the sink.

What makes up our sewerage network?

  • 400 kilometres of sewers
  • 3 main trunk sewers
  • 9 pumping stations
  • 2 treatment plants

How the sewerage system works


Each year, more than 320,000 million litres of sewage enters the system through a network of underground pipes. This sewage comes from homes as well as businesses. Businesses need permission to use the sewers because their trade waste is more contaminated.


Sewage then enters one of three larger trunk sewers. These slope downwards so gravity helps the sewage flow. Eventually, pumping stations push it up to ground level to be processed at a treatment plant or continue its journey through the sewerage system — which can take up to 12 hours.


Our Eastern Treatment Plant and Western Treatment Plant process sewage in different ways, removing rubbish, organic matter and chemicals. The clean water can then be released into the environment or disinfected to supply as recycled water.

Maintaining the sewerage system

We constantly monitor and maintain our sewerage system to keep it in good working condition. This involves:

  • inspecting sewers through closed circuit TV
  • cleaning sewers
  • trimming tree roots to prevent blockages, using high-pressure water jets
  • major works and projects to replace aging pipes or increase their capacity

Sewer spills

Although we have a world-class sewerage system, sewage can still overflow sometimes. This happens when sewer pipes are:

  • blocked or broken by tree roots, fats or oils
  • too full after heavy rain, so very diluted sewage is released into rivers and creeks

This animation provides information on sewer spills, which can still happen despite Melbourne's world-class sewerage system.

Sewer spills video - transcript

How you can help

  • don’t flush fats, oils or other dangerous chemicals down the sink or toilet
  • check your stormwater plumbing isn’t connected to the sewerage system
  • install a water tank to capture rainwater
Last updated:
30 October 2017