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Looking for defects on the wastewater network

Council has started a ‘smoke’ testing programme across our wastewater network.

Smoke testing involves injecting a non-toxic, odourless white vapour - or ‘smoke’ (the same used in smoke machines) - into the manholes across our wastewater network and is common practice in New Zealand. It is used to detect where stormwater may be entering the wastewater network. As the vapour travels through the system, it reveals the location of any breaks or weakness.

Before we undertake smoke testing in a particular area, we notify the property owners and residents who may be affected by mail. We also advise the fire service of the work underway.

However if you are out and about in an area where our contractor Pipe Vision is undertaking this work, you may see smoke coming out of drain grates, manhole lids and downpipes. Please do not be alarmed as this is a normal part of the process.

Below are answers to some frequently asked questions about this work.

If you have any other questions please call us on 06 857 8060 (24 hour service) or email

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Smoke testing involves injecting a dense, non-toxic and odourless smoke into the drainage system at a manhole and watching to see where the smoke escapes to detect where stormwater may be entering the wastewater network. The ‘smoke’ is not a true smoke, it is the same non-toxic substance used in smoke machines. It is considered safe for humans, animals and plants. It will not leave residue or stains and is not a fire hazard.

Our wastewater network is designed to collect wastewater from properties, not stormwater and other surface water. When stormwater enters the wastewater network it can overwhelm the capacity of the network, which can cause issues such as wastewater network overflows, affect our treatment processes and harm our environment. Smoke testing helps to identify where stormwater may be entering the wastewater network. Smoke testing is a common practice.

If your plumbing is installed and working properly, and all “traps” are filled with water, no smoke will enter your home. If we find a defect on your property we will send you a notice. A list of common defects can be found on our website under ‘What is a defect?’.

During smoke testing, crews blow air and an odourless white vapour into the sewer system through manholes. The smoke fills the main sewer pipe and any connected pipes and follows the path of any leak to the ground surface. Crews monitor where smoke escapes the system to find the leaks.

We will need to access your property to inspect your wastewater and stormwater pipes. Our contractors will need to take photos of your gully traps and downpipes; we may pour a safe, non-toxic dye down your stormwater drain; put a CCTV camera down your gully trap to identify breakages; or use a theatrical smoke machine on wastewater pipes. You may see ‘smoke’ coming out of your pipes or out of the ground. Please do not be alarmed.


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