Knowing Your Pipes

As part of our Global Stormwater consent conditions, we regularly monitor the water quality in our stormwater network. If a sample from one of these tests is above the trigger levels, we will investigate. During an investigation we will take water samples from different locations to help target where the pollution is coming from.

We use smoke testing to investigate faults in the wastewater and stormwater networks. To do this, we put a dense and non-toxic smoke fluid into a smoke machine that emits vapour through the pipe network. This testing is looking for four things:

• A connection of stormwater to wastewater

• Leaking of wastewater into stormwater or directly into waterways

• A connection of wastewater to stormwater

• Pipe faults such as cracks in both private and public pipes.

If we find one of these faults, we’ll work to correct it as this can have a harmful effect on the environment, as well as increase treatment costs.

During the smoke test we will also conduct above ground inspections to ensure there are no entry points that allow stormwater into the wastewater network, i.e. Broken gully trap surrounds, low gully traps and a connection of stormwater downpipes and yard drains.

A gully trap is a plumbing feature that should only receive wastewater from your kitchen, bathroom, and laundry. It connects to the wastewater network and is treated. The top of the gully trap needs to be above ground level and partially covered to stop water and objects getting into the wastewater network.

We use CCTV (closed-circuit television) to assess pipe conditions so we can make sure the public and private pipes are working the way they are meant to. 

If we find a fault and need to investigate it further, we will use dye tracing. This involves pouring a non-toxic, fluorescent green dye into gully traps and drains and flushing it with water. We will then look for places where the dye is released, including private drains. 

We have installed flow and level sensors in some parts of the wastewater network to help us understand how the network is operating. These sensors aid us to monitor flow levels during rainfall which also helps us predict and prevent wastewater overflows.

As pipes age and the ground moves, pipes can become less watertight. This means wastewater might be slowly leaking (exfiltrating) out of a pipe and into the groundwater. This sort of leakage is hard to detect using the other forms of investigation (dye testing and CCTV). In this instance, we may need to do a hydrostatic (or pressure) test to check for water tightness. We can do these tests on both the public and private network.