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I&I Study

Smoke Test FAQ

The City of Portland has started a Sanitary Sewer Infiltration & Inflow (I&I) Study as part of a sewer system condition assessment. I&I studies are used to locate possible deficiencies in the wastewater collection system that may allow storm or ground water to enter the system. The results will help prioritize and plan future wastewater maintenance and rehabilitation projects, and is being done as part of a preventative maintenance program so that any issues can be proactively addressed.  

Pipeline Analysis, an engineering firm specializing in wastewater collection systems, will conduct the field tests and monitoring. The company is headquartered in the Dallas/Fort Worth area.   

As part of the study, “smoke” testing of the sewer lines will be done to locate any breaks or defects in the system. The petroleum-based “smoke” product has been used for more than 30 years. It is not toxic to humans or pets, leaves no residue, and creates no fire hazard.   

Smoke testing allows inspection of both the main lines and laterals. The smoke travels throughout the system, identifying problems in all connected lines. Best results are obtained during dry weather, which allows smoke better opportunity to travel to the surface.  

During the tests, smoke mixed with large volumes of air is blown into the sanitary sewer line usually through a manhole cover. Smoke will identify broken manholes, uncapped lines, and even cracked mains and lines.    

Residents will be notified 48 hours prior to smoke testing in their area with a door hanger. (A current testing schedule will also be posted on the homepage of and on the City Facebook page.)  

During testing, residents may notice smoke coming from roof vent stacks or up from the ground. This is a common visual test and poses no reason for concern. The smoke should not enter your home unless you have defective plumbing or dried drain traps. If this does occur, you’re encouraged to contact a licensed plumber for repairs. If the harmless smoke can enter through faulty plumbing, the potential exists for sewer gases to enter your home. When notified of pending testing, it is recommended that residents pour a gallon of water into drains that are seldom used to prevent “smoke” from entering through unused drains.   

The study will also include dye testing, manhole inspections, and internal cleaning and TV inspection. Dye testing involves using a non-toxic dye injected into cross-connections, roof drains, and area drains that are suspected of being connected to the sanitary sewer. Manholes can be a significant source of extraneous infiltration/inflow, reducing the system’s wet weather capacity.  

Some sewer lines and manholes may be located on the backyard easement of property lines. In some cases, inspection crews may ask for access to the easements for sewer lines and manholes. Pipeline Analysis personnel are uniformed and carry identification badges. Homeowners do not need to be home during this project and at no time will field crews need to enter your home. The notification door hanger will list a phone number that residents can use to call with any questions or concerns.   

The field portion of the study will be conducted throughout the winter and early spring. New residential and commercial areas, as well as areas covered in previous I&I studies, are not included in this study.

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