Regional Infiltration and Inflow Control Program

Out in the Field - Finding and Fixing I/I > Smoke Testing

Smoke Testing

Smoke Testing portions of the sanitary sewer pipes involves pumping smoke through sanitary sewers from utility holes in streets or within public easements and observing and documenting where smoke exits. Depending on the specific circumstances, the exiting smoke can indicate the location of a broken pipe, manhole, catch basin, or where roof or foundation drains might be connected to the sewer system, indicating where infiltration or inflow might enter the sanitary sewer system.

During the testing, smoke will typically appear from roof drains, catch basins or yard drains connected to the sewer system. The smoke may also appear from cracks in the pavement above the sewer, from landscaping above private connecting sewers, and around homes with foundation drains connected to the sewer.

Under some conditions, smoke may also appear in basements through unused floor drains, disconnected or faulty plumbing fixtures, and other direct openings to connecting sewers. Before the scheduled day of smoke testing, residents in the pilot areas to be tested were given notice and advised to pour one quart of water down all floor drains, sinks or other plumbing fixtures not used regularly. The smoke, manufactured for this purpose, leaves no residuals or stains and has no effects on plant and animal life. The smoke has a distinctive but not unpleasant odor. Visibility and odor last only a few minutes, where there is adequate ventilation. This smoke is nontoxic, harmless and creates no fire hazard. Typically local fire and police authorities are notified and the inspection team is available at test sites to answer questions during the smoke testing.

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For questions about the I/I Control Program Web site, please contact Maryann Petrocelli at 206-263-7321 or maryann.petrocelli@kingcounty.gov.

Department of Natural Resources and Parks
Wastewater Treatment Division

Updated: Jan. 15, 2008

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