Sewer Testing

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We test the sewers to find leaks before they become larger problems. This testing is essential to keep our sewer system working well. We test our sewers by putting simulated smoke into the sewers to find leaks and faulty connections. The test lasts about 30 minutes, and people may see the simulated smoke coming from manhole covers, storm drains, roof vents or building foundations.


Where and when we are testing our sewers:

We will be doing our annual sewer tests this summer from June 1 through September 30.

Please see the project area map  and sewer testing notices that have been mailed to residents and property owners.


How the test could impact you:

Property owners will receive a sewer testing notice to alert them that testing will be conducted in the neighborhood. The simulated smoke is not expected to enter your home or building, but if it does, don’t be alarmed – simply open doors and windows to ventilate the area. The simulated smoke should clear out quickly. The simulated smoke is safe, but may cause some irritation.

If there is an individual in your home or building who has respiratory problems and/or mobility limitations, please contact the City's contactor, S.E.H. at 612-219-4231.

What you need to do:

If you see the simulated smoke in your home, there is no reason to be alarmed, but please call the City's contractor at 651-238-0572.

Information about sewer smoke testing

The Process:

  • Simulated smoke will be injected into the sewer system. As a result simulated smoke may be seen coming from manhole covers, storm drains, roof vents, and building foundations.
  • The sewer test will last approximately 30 minutes.
  • Inspection crews will not need to enter buildings, unless to gain access to building rooftops.
  • Faucets and bathroom facilities can still be used during sewer testing.

Tips to prevent simulated smoke from entering your home or building (complete prior to test):

  • Run water faucets for a few seconds in unused sinks, tubs, and drains to fill fixture traps.
  • Pour water into each floor drain (at least 1 gallon)
  • If you have defective plumbing (i.e. no trap), you should consult with a licensed plumber.

If you notice simulated smoke in your home or building:

  • Do NOT become alarmed.
  • Open doors and windows to ventilate the premises to simulated smoke.
  • Contact the City's contracted sewer testing crew at (651) 238-0572.
  • Simulated smoke will not stain walls or furniture; nor will it leave a residue.
  • ​Contact a licensed plumber in the near future to find out if you have a problem with your sewer connection.

Safety and Health Concerns:

  • There is NO danger in the sewer smoke testing process. The simulated smoke will not cause a fire or explosion.
  • St. Paul Police and Fire Departments will be notified of the sewer safety testing.
  • Simulated smoke is not harmful to your health, but may cause some coughing. Simulated smoke irritation is temporary and should disappear after exposure has ceased. If you do encounter the simulated smoke – avoid unnecessary exposure to it.
  • The simulated smoke is not harmful to pets, but it would be a good idea to leave windows partially open for ventilation, should any smoke enter the building.
  • If you have proper plumbing connections and all of the drain traps have water in them, there should not be any problem.
  • If there is an individual in your building, business, or residence who has respiratory problems and/or mobility limitations please contact the City's contract at 612-219-4231.
  • A copy of Material Safety Data Sheet (MSDS) for the simulated smoke.





For further information on the LiquiSmoke product used in testing our sewers, as well as material testing results regarding exposure and health please visit: