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.
TV inspections record conditions using a TV camera within the pipes. Closed Circuit TV (CCTV) cameras have been developed that can be slid down sanitary sewer lines and record a "movie picture" of the conditions that are found in that section of sewer. This can identify breaks, root intrusion, leaking water (especially infiltration from groundwater), and general deteriorating conditions. Estimates can be made for how much infiltration might occur from such leaks.
Manhole inspections are known to be a relatively inexpensive and quick method of detecting inflow/infiltration sources in storm and sanitary sewer systems. Visual manhole inspections provide an additional source of information concerning the presence and degree of inflow/infiltration problems, the general structural condition of the manhole and the accuracy of previous system drawings. Visual manhole inspections can be used to determine the following:
- The exact location of the manhole
- The condition of cover and frame (including defects that would allow inflow to enter the sanitary sewer system)
- Whether the cover is subject to ponding or surface run off
- The potential area that drains to any defects
- The condition of benching, risers, grade rings and collar, and
- The condition of sewer pipe and lateral connections.
Flow Monitoring: The City needs a way to accurately measure the amount of water moving through its collection system in order to deductively pinpoint sources of I&I. This issue in the past has been addressed through unreliable and inaccurate inference; however, in 2004 the City purchased five Mag-Master MFE Series Electromagnetic Sensors. These permanent flow meters are being installed in five strategic locations around the city providing a true measurement of the amount of wastewater being carried by the City collection system. The information gathered from these devices will help to identify, monitor and manage the City’s I & I issues.
Repair and Replace: As inspections paint a picture of the City underground sewer collection system defects are found and scheduled for repair or replacement.