Sanitary Sewer Smoke Testing 

The Bristol Water and Sewer Department contracted with Flow Assessment Services to conduct Sanitary Sewer System Smoke Testing for the purpose of locating sources of storm water inflow to the sanitary system. The study will locate direct and indirect connections such as catch basins, area drains, roof drains, broken sewer pipe and deteriorated pipe joints. During this test, harmless white smoke is introduced through the sanitary sewer system via a smoke-generating machine. During this procedure, white smoke will be venting from holes in manhole covers located on the street and plumbing vent pipes located on or near your roof surface.  

Smoke should not enter your premises unless there is a dry trap in your basement floor drain or any unused plumbing fixtures. You may wish to pour some water down your basement drain or unused plumbing fixture to ensure that the drain trap will be effective. Smoke could also enter the building through defective plumbing. The owner should note this because gases from the sewer system may possibly enter your building through the defective plumbing.


Should smoke be detected within the building, DO NOT BE ALARMED. The smoke is NON-TOXIC AND NON-STAINING. Simply ventilate the home and report the presence of smoke to the people conducting the test outside in the vicinity of your building. If possible, they will assist you in locating the source that allowed the smoke to enter the building.

Make sure your P-Traps have water in them to avoid smoke from entering your residence.

P trap

Example of normal escape route for smoke during a sanitary sewer smoke test.

NORMAL - vent stack
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Common Examples of What you Can Expect to See

  1. 1 drain
  2. 2 ground drain 2
  3. 3 ground drain
  4. 4 ground gutter
  5. 5 manhole cover
  6. 6 roof gutter
  7. 7 storm water grate