Water crews guide portable television cameras through the wastewater system pipes to determine any sources of inflow or infiltration.
Filling the wastewater system lines with smoke and watching where it emerges can identify many sources of inflow. The smoke is kept from entering buildings by the drain traps required on all sanitary fixtures and drains. It will emerge from the sewer stand-pipe vents on the roof of buildings, from improper connections such as downspouts, and it may also emerge from holes in the ground that lead to leaks in sewer lines.
Santa Rosa Water can monitor the amount of water flowing through wastewater system by inserting special measuring devices into the sewer lines. If the flow increases during rainstorms, it's a sure sign of infiltration.
Smoke Testing (PDF)