skip to main content

I want to...

Current filter:

Smoke Testing in our Wastewater Network

We are undertaking a programme of smoke-testing in our wastewater network. While this programme is in progress, you may see smoke coming out of drain grates, manhole lids and downpipes.

When we do smoke testing we push a dense, non-toxic, odourless smoke into the drainage system to see where the smoke escapes. It's normal for smoke to come out of the wastewater vent pipes on roofs of homes and buildings, this doesn't mean there’s a problem. If smoke comes out of storm drains or rises from lawns, pavements or the street, this can mean there is a problem like a cracked wastewater pipe, damaged manhole or a cross-connection to/from the stormwater network.

The ‘smoke’ we use in this testing programme is not actually smoke. It’s similar to the vapour used in smoke machines at concerts and parties. It is considered safe for humans, animals and plants. It doesn’t leave residue or stains. It is not a fire hazard and will disappear quickly without leaving a smell.

If the smoke comes into your home, please open windows at each end of your house and the smoke will disappear in a few minutes. Smoke appearing in your home may indicate that there is a problem with the plumbing in your home. Please contact a licensed plumber to make any necessary repairs.

The drainage network made up of the exclusive stormwater and wastewater pipelines that are designed to collect either stormwater or wastewater respectively, not both. When the wastewater enters the stormwater network it has potential to harm and contaminate the receiving waterways. When stormwater enters the wastewater it stresses the network and can cause overflows. The purpose of the smoke testing is to identify areas within the network where there might be cross-connection between wastewater and stormwater.

A guide to Smoke Testing and what it means for you

Council is about to begin a smoke testing programme in Napier. This work will be undertaken at various manhole locations around the network. Below are some FAQs that have been compiled to help provide more information on this work.


Smoke testing involves injecting a dense, non-toxic and odourless smoke into the drainage (sewer or stormwater) system at a manhole, and watching to see where the smoke escapes. The smoke fills the main pipe and any connected pipes, and follows the path of any breaks in pipework to the ground surface.

The purpose of smoke testing is to identify areas within the wastewater or stormwater network that need attention.

Our stormwater is designed to collect only rainwater runoff from roofs, roads and other impervious surfaces. Smoke testing will help identify any wastewater connections (cross-connection) to the stormwater network which can result in contamination and harm to the waterways or estuary.

Similarly, our wastewater network is designed to collect wastewater from properties, not rainwater and other surface water. When other water enters the wastewater network, it can overwhelm the capacity of the network (especially in heavy rain events). This can result in overflows of diluted untreated wastewater into the waterways and estuary and can have a harmful effect on our environment. Excessive stormwater that arrives at the wastewater treatment facility can also wash away the special bugs that treat our wastewater. This affects our treatment processes. Smoke testing will help identify any stormwater connections to the wastewater network (cross-connection).

Smoke testing also identifies breaks in pipes and manholes as well as locations where stormwater.

Smoke testing is common practice around New Zealand.

Before each new round of smoke testing, we notify the residents who may be affected.

We do this by:

  • Sending a letter to all houses in the area selected for testing
  • Posting on Council Facebook groups

We also advise the fire service that works will be undertaken.

No. The “smoke” is not true smoke. It is a harmless white vapour – the same non-toxic substance used in smoke machines at concerts. It is considered safe for humans, animals and plants, leaves no residue or stains, is not a fire hazard and will disappear rapidly without leaving an odour. Since any vapour can be an irritant, direct contact with the smoke may cause minor respiratory irritation in some people.

People with respiratory problems such as chronic asthma or emphysema should avoid direct exposure to the smoke. Please contact Council, phone to discuss your situation further if you have concerns about upcoming smoke testing.

Smoke appearing in your home may indicate that there is a problem with your plumbing. We suggest you contact a licensed plumber to inspect and make necessary repairs if you see smoke in your home during our testing.

If your plumbing is installed and working properly, your U-traps will prevent smoke entering your home. A U-trap is a U-shaped section of your drain pipe that is always full of water. The water acts as a barrier, preventing sewer gases from getting into your home through sinks and drains. If there is no water in the trap, it will not work properly. Dry traps are most often found in floor drains and bathroom drains that aren’t used often. We recommend running some water into infrequently used drains or fixtures prior to smoke testing.

  • Do not be alarmed.
  • Open windows to allow ventilation and note where the smoke is coming from; it will clear in a few minutes.
  • Leave your home and notify smoke testing personnel in the area. This is precautionary until we confirm that the smoke is from our testing and is not indicative of fire.
  • Remember, if smoke enters your home during the test, there may be problems with your plumbing. These problems could allow potentially dangerous sewer gas to enter. Please contact your plumber immediately.

If you have any doubt as to the source of the smoke in your home or property and suspect a fire, please call 111.

  • Ensure all drain U-traps contain water by running some water into all drains and fixtures before smoke testing. This is particularly important for floor drains and bathroom drains that aren’t often used.
  • If there is an individual in your home or business with respiratory problems and/or mobility limitations, or if you have any additional questions, please contact Napier City Council, phone 06 935 7579

Smoke testing focuses on the public part of the sewer system which Council maintains. While the testing can also identify plumbing problems on private property, this is not the main intent of the smoke test. It is the homeowner’s responsibility to maintain private plumbing connections. Please contact your plumber if you have any concerns about plumbing on your property.

Yes, smoke alarms may be activated during smoke testing. If possible, open windows and/or doors for ventilation. If you have any doubts about the origin of the smoke, call 111.

We can’t do smoke testing when it’s rainy or very windy, so the weather can sometimes cause delays. However, we will let you know the period in which we will be smoke testing your area by mail.

If we are smoke testing the wastewater network, smoke will be seen coming from sewer vents (also known as terminal vents) on roofs of homes. This is normal and indicates that smoke has filled the sewers. Smoke may also be seen coming from building foundations, manhole covers, or cleared sections with existing sewer connections.

If we are smoke testing the stormwater network, smoke will be seen coming from roof guttering, road sumps and manhole covers.

No, the smoke is a vapour and cannot block the pipes.

Council will use the findings to help plan future public infrastructure improvement projects and to identify changes required to stop storm water and other surface water from getting into the sewer system or vice versa. Depending on the findings, we may also undertake immediate repairs to the sewer system.

As there may be Council services located in your property, Council staff or representatives may require access to your property to check that smoke is exiting from the expected locations. Council will not require access inside the building or house and you do not need to be home during the smoke testing.

For any queries or further information regarding smoke testing, please contact Customer Services on 06 935 7579.

Napier City Council - Copyright © 2024 Napier City Council

Disclaimers and Copyright
While every endeavour has been taken by the Napier City Council to ensure that the information on this website is accurate and up to date, Napier City Council shall not be liable for any loss suffered through the use, directly or indirectly, of information on this website. Information contained has been assembled in good faith. Some of the information available in this site is from the New Zealand Public domain and supplied by relevant government agencies. Napier City Council cannot accept any liability for its accuracy or content. Portions of the information and material on this site, including data, pages, documents, online graphics and images are protected by copyright, unless specifically notified to the contrary. Externally sourced information or material is copyright to the respective provider.

© Napier City Council - / +64 6 835 7579 /