Sanitary Sewer Smoke Testing

The City is conducting smoke testing to identify locations where storm water is entering the City's sanitary sewer system. 

What is Sanitary Sewer Smoke Testing?

Smoke testing is a simple means of locating openings in the sewer system that allow surface rainwater runoff to enter the sanitary sewers. Air combined with non-toxic smoke is forced into sewer lines to disclose the location of leaks and connections. Smoke will appear where there are defects in the main sewer line (usually located under the road) or laterals (connection between the main sewer line and a building) or where other connections to the sewer system exist, such as roof drains, patio drains and footing drains.

2023 Locations
Smoke testing is scheduled to begin the week of July 31, 2023 and be completed within one week (weather permitting). Please note – there will be no smoke testing in the Central Business District on Lake Forest Day (Wednesday, August 2). The smoke testing study is being performed by the engineering firm RJN Group, Inc. View a map of smoke testing areas below.

2023 Smoke Testing Area Map

What to Expect
Smoke will not enter buildings unless there is defective plumbing or dried-up drain traps. It is expected – and normal – for smoke to come out of the sewer vent stack on the roof of a building during the test.

The smoke is non-toxic, creates no fire hazard, leaves no residue, dissipates quickly and is harmless; however, those with respiratory issues may wish to take extra precautions, such as leaving the area for a few hours until testing is complete. 

Watch the video below to learn more about what to expect.

What To Do If You See Smoke
You should always feel free to call 9-1-1 in an emergency. If you believe smoke is entering your home from the smoke testing, simply open a window and the smoke will dissipate quickly. Also, please contact a member of the RJN crew if they are still on your street. If the RJN crew is no longer in the area, contact the RJN Group office at (630) 682-4700.

Additional Information
For additional information on smoke testing, visit the Smoke Testing FAQs webpage. If you have any questions, please contact Engineering Assistant Jim Koblas at (847) 810-3553 or

Stay Informed!