Wastewater Network

​Wastewater network facts

  • 797 km of pipes ranging from 100mm to 1800mm in diameter
  • 15,074 manholes
  • 53,251 connections
  • 132 pumping stations
  • 6 major wastewater pipeline bridges
  • 1 wastewater treatment plant

Infiltration and Inflow to the wastewater system (I/I)

Infiltration and inflow refers to stormwater that has flowed into the wastewater network.

Infiltration is stormwater which seeps into the ground and enters the wastewater network through cracks and defects in the pipes.

Inflow is stormwater that enters the wastewater network from low lying gully traps and roof downpipes that connect directly to the sewer.

During periods of heavy rain, increased inflow and infiltration can overwhelm the wastewater system and cause overflows. This reduces the network capacity, increases the cost associated with extra wastewater pumping and treatment and can lead to the contamination of private properties.

In order to manage the risks, property owners are required to ensure stormwater does not enter the wastewater network. If you have one of these occur in your property, you must contact a plumber straight away to have it rectified. 

  • Stormwater flows into your gully traps that are too low.
  • Downpipes from your roofs lead to wastewater pipes/your gully trap.
  • Drainage pipe joints leak or cracked pipes.​
Page reviewed: 18 May 2020 2:58pm