Help us protect Tasmanian waterways and parklands

Stormwater inflow and infiltration

Our sewerage network is not designed to manage the inflow and infiltration of stormwater during rainfall.

Inflow is where stormwater enters the sewerage network, generally via private plumbing that is incorrectly connected to the sewer.

Infiltration is stormwater entering the sewerage network, generally by seeping through cracked, or unsealed underground infrastructure.

Below is a diagram that shows a correctly plumbed and incorrectly plumbed property.

The effect of inflow and infiltration

When the amount of stormwater entering the sewerage network exceeds the network's capacity, there is potential for the following:

• overflows to creeks, rivers and parklands
• increased risks to the health of our waterways and local environment
• increased sewage pumping and treatment.

Vapour testing helps TasWater identify where stormwater may be entering the sewerage system.
We map out the drainage connections in an area, carry out testing, and monitor for any release of vapour.

During testing, a non-toxic, odourless vapour (which looks like fog) is gently released into parts of the stormwater and/or sewerage network. This allows us to see where the vapour escapes, helping locate possible cross-connections or leaks.

You may notice mist or fog coming from maintenance holes, sewer vents, or street grates while testing is underway. This is completely normal and shows that the system is being tested.

If you see vapour coming from inside your property, such as from a sink, toilet, or floor drain:

• Open doors and windows to let in fresh air.
• Contact TasWater on 13 6992, or let the testing contractors know if they are nearby.

The vapour is safe, odourless, and will quickly disappear, but letting us know helps us confirm the results and maintain accurate testing records.

Dye testing is one of the ways TasWater checks that stormwater and sewerage systems are working as they should.

It’s a simple, safe, and effective method that helps protect the environment and public health.

During testing, a small amount of fluorescent dye mixed with water is poured into stormwater drains or downpipes. Our team then monitors a nearby sewer maintenance hole.
If the dye appears in the sewer system, it means there may be an incorrect connection between the stormwater and sewerage networks. These cross-connections can cause sewage overflows during heavy rain and may impact local waterways.

The dye is odourless, non-toxic, and environmentally safe. It’s commonly used by water utilities across Australia and poses no risk to people, pets, or the environment. The colour will naturally fade within a few hours.

TasWater has engaged Detection Services to install iTrackers within our sewer network to help identify areas affected by inflow and infiltration (I&I).

The monitoring involves a series of ultrasonic level sensors placed in sewer maintenance holes. These sensors record wastewater levels, and specialised software converts this data into flow measurements.

By tracking these flows - particularly after rainfall - we can identify parts of the network experiencing higher-than-expected volumes, which may indicate stormwater entering the sewer system.

This monitoring plays an important role in helping us locate and fix issues such as leaky pipes, damaged manholes, or incorrect private property connections, supporting more efficient maintenance and a healthier environment.

We’re inspecting sewerage infrastructure in areas where sewage overflows occur regularly or where there are known environmental impacts.

Our crews are working to identify and repair leaks, cracks, and incorrect connections within TasWater’s network to improve performance and reduce overflows.

If we identify any issues on privately owned plumbing or stormwater systems, we’ll contact the property owner and provide clear guidance on what needs to be fixed and how to do it safely.

This shared approach helps ensure that both public and private infrastructure are working together effectively — protecting homes, public health, and Tasmania’s waterways.

We all share a role in helping reduce sewer overflows and protecting our waterways.

One of the simplest ways to make a difference is by making sure your property’s plumbing is connected correctly.

As part of this program, TasWater will be checking that downpipes are connected to the stormwater system — not the sewer network.
Stormwater entering the sewer can overload the system during wet weather and lead to overflows in homes, streets, and the environment.

✅ Correct connection

• Downpipes lead to the stormwater system (e.g., kerb, gutter, or stormwater drain).
• Overflow Relief Gully (ORG) is at least 150mm above ground level and clear of obstructions.
• Gully grates are open to allow sewage to escape outside in the rare event of a blockage.

❌ Incorrect connection

• Downpipes connected to a sewer inspection point or gully.
• ORG is below ground level, covered, or concreted over.
• Stormwater drains connected into the sewer network.