Smoke Test Inspection

A smoke test inspection is a simple, cost-effective test for identifying infiltration into a closed system, such as ground water or storm runoff entering a sanitary sewer system. These leaks or intentional tie-ins (illegal connections) to the wastewater system allow rainwater to enter, thus creating overflows, backups, and additional wastewater treatment costs.

Smoke testing involves introducing a non-toxic vapor (smoke bomb or liquid smoke) into the system for testing purposes. A high-powered blower or fan (usually powered by a gasoline engine) is placed on top of an open manhole at either end of the testing section to force the smoke exiting the system at various locations. Smoke plumes coming from areas other than the manhole rim indicate defects, such as cracks or bad joints where seals are in need of repair, or illegal cross connections with the stormwater system, and are marked with flags, photographed, and/or measured from stationary landmarks.

Other manholes can be partially blocked by lowering sandbags to further isolate the line. However, completely blocking the line causes water to back up and prevents smoke from traversing the pipe. Smoke testing is not effective after rain or when ground water is unusually high.