2023 Sanitary Sewer Smoke Testing Program

The City of St. Charles is conducting a program to identify locations where storm water is entering the City sanitary sewer system.  The study, being performed by the engineering firm RJN Group, Inc. of Downers Grove, IL, includes smoke testing of the sanitary sewers on the east side of the City.  The testing is scheduled to begin during the first week in October and is expected to be completed by mid-October, weather permitting.  All affected residences and businesses are notified prior to testing and signs also will be posted in the neighborhoods being tested. 

Smoke testing is a simple means of locating openings in the sewer system that allow surface rainwater runoff to enter the santiary sewers. Air combined with non-toxic smoke is forced into the sewer at manholes, often located in the street, filling the system.  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.  During the test, smoke may be seen coming from vent stacks on the roof and out of the ground.

Smoke will not enter homes or buildings unless the plumbing is defective or drain traps are dry. The smoke has no odor, is non-toxic, low odor, creates no fire hazard, leaves no residue, dissipates quickly and is harmless; it is similar to the special effects smoke used in concerts and haunted houses.  Pour 1 gallon of water down all floor drains and any rarely used sinks/tubs/toilets to ensure that a water barrier is maintained in the drain traps and into any unused sinks prior to the test will seal the drain traps so smoke will not enter through the drains.

Why Test the Sanitary Sewer Lines for Faults?

  • Reduce Inconvenient Sanitary Sewer Backups - When a significant amount of ground water flows into the sanitary sewer system through faulty lines, it can overwhelm system capacity and cause sanitary sewer backups.
  • Eliminate Unnecessary Wastewater Treatment - All water in sanitary sewer lines is treated at the City’s wastewater plant. Significant amounts of groundwater flowing into the sanitary sewer mains can lead to millions of gallons of water being treated unnecessarily.
  • Identify Location of Sanitary Sewer Gas Leaks – Faulty sanitary sewer mains or connections could allow sewer gases to escape.

For more information about the Smoke Testing Program, contact St. Charles Public Works Department at 630.377.4405.


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