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Sewer System Smoke Testing

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Purpose & Goals

The City of Longmont performs sewer system "smoke testing" to help locate obstructions and defects in the sanitary sewer system. Specifically, it is a form of inspection that evaluates sewer conditions or connections that could allow storm water to enter into the sanitary sewer. Storm water can cause capacity problems in the sewer and increase wastewater treatment costs, which affects your monthly utility bill.

The information gained from smoke testing contributes to the City’s ability to control costs and maintain a high level of service for the Longmont community.

Upcoming Testing

Trunk 6

  • Serves a commercial/industrial area located in central Longmont - view map of area >
  • Investigation is anticipated to begin in early June 2018 and continue through the summer months.
  • The investigation will be supervised by City staff and carried out via contract with CH2M Engineering.
  • Inspections will occur during normal business hours between 8 a.m. and 5 p.m. Monday through Friday.

The Test

Smoke testing involves the introduction of a specially formulated smoke into a local sewer line and pressurizing the system with fans located at manholes to see where smoke comes out. The smoke used in the test is not harmful to humans or pets, creates no fire hazard and is approved by the Environmental Protection Agency.

If the sewer is in good condition, that is, there are no pipe defects or damage, improper storm sewer connections or plumbing defects, then the smoke should only come out through plumbing vents in building roofs, or farther down the line through sanitary sewer manholes. However, if there are defects in the sewer, improper connections, or plumbing defects, smoke may escape at other locations. In those cases, smoke may escape from peculiar places such as pavement cracks, turf areas, rain downspouts on roofs, driveway drains, yard or area drains, window well drains, foundation perimeter drains, defective service pipes, and possibly inside buildings.

Frequently Asked Questions

  • Sewer Smoke Testing

    • How do I prepare my home/business for smoke testing?

    • Is it normal for the sewer vent on my roof to smoke during the test?

    • Is the smoke harmful to me or my pets?

    • What happens if smoke enters my house?

    • When will the smoke test be performed at my address?

    • Who will I see doing the testing?

    • Why did smoke enter my home?

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