Understanding Smoke Testing
Smoke testing is used to detect storm water inflow sources such as roof downspouts, driveway and yard drains, foundation drains, and storm water drainage system cross connections. It can also detect structural deterioration and leaking joints in sewer pipes. Smoke testing is one of the most efficient and cost effective methods of locating sources of I/I within sewered areas.
Smoke escapes from the grass near a sanitary lateral defect.
Smoke is seen coming from a missing lateral clean-out cap.
How does smoke testing work?
City of Boone staff will complete the field work associated with the smoke testing project. City crews have a two to three man crew use a high capacity blower and force “smoke” down into manholes. The smoke, under pressure from the blower, travels through the sewers and escapes through any connections, defects, cracks, leaks, etc. along the way. This quickly reveals sources of inflow and infiltration within the study area. After placing the blower and filling the lines with smoke, the contractor will perform a visual inspection of where the smoke is escaping. Close attention is given to sanitary lateral clean-outs and roof downspouts. It is not uncommon, however, to see smoke coming out of the grass, wooded areas, or cracks in pavements. All smoking sources are documented via measurements and pictures/video to make it easier to find these sources at a later date. The smoke is non-toxic and non-hazardous and is manufactured specifically for this purpose. It leaves no residuals or stains, and has no effects on plants or animals. The smoke should not enter your home, but if it does, it will have a distinct odor and should only last a few minutes with proper ventilation. Please note, all plumbing fixture drain traps must be filled with water prior to smoke testing. See instructions below.
Important Instructions for Residents Prior to Smoke Testing:
- Make sure all drain traps and plumbing fixtures have water in them. Fill seldom used drains (such as basement floor drains, garage sinks, etc.) with water by running the faucet for 30 - 60 seconds or filling the drain with approximately 3 cups of water. This will prevent smoke from entering your home.
- Prepare drains as soon as you receive the smoke testing notice, this only needs to be done once before testing begins
- You do not need to be home during the smoke testing field work
- Smoke should not enter your home, however, if it does this could be an indication of a defect in your plumbing system. This defect could allow sewer gases to enter inside your home, which is a potential health hazard. Corrections of such defects on private property are the responsibility of the property owner, and a licensed plumber should be consulted to ensure the proper corrections are made. If smoke does enter your home or building, please notify the field technicians who are conducting the test.
After smoke testing has concluded...
The smoke testing contractor will provide the City with a list and photo/video documentation of deficiencies uncovered throughout the smoke tested areas. Deficiencies will be in both the City right-of-way as well as private property. The City will prioritize the problem areas and start work to correct issues right away. Identified I/I sources or deficiences will need to be corrected in a timely manner. If smoke sources are found on your property, the City will provide a letter to the property owner explaining the deficiencies found and giving him/her options on how to correct them. This letter will have a specific deadline for corrections of deficiencies. Often times, deficiencies can be easy fixes, such as disconnecting downspouts from the sanitary lateral, or replacing a missing or broken lateral cleanout cap. A list of licensed sewer contractors will also be included in the letter. For more difficult corrections, the City will give an extended deadline and ask that the property owner contact a licensed sewer contractor for consultation. More difficult corrections could include cracked sanitary laterals, tree root issues, or re-routing drainage. It is impossible to know the extent of these more difficult corrections until testing is underway. Remember, correcting these problems will be beneficial to everyone involved. Keeping sewer rates low and preventing water quality violations are the goals of this work. After the results from smoke testing have been reviewed, the City will provide detailed procedures for fixing the most common problems on this website. Also, project status updates will be made to keep residents informed of where the project is currently and where it will be heading next. Feel free to check back often to stay up to date on the progress of this project as well as the I/I Reduction Program.
Correcting I/I Sources on Your Property
Clean-out Caps
A broken/missing or non-watertight sanitary lateral clean-out cap can allow excess storm water to enter the sanitary sewer system. This is especially true when the clean-out cap is in a low lying area or within an impervious surface. Clean-out caps can be relatively easy to change and under most circumstances, the broken cap can be removed and a new water tight cap can be put back into place.
Downspouts
Downspout connections can add as much as 800 gallons of clean storm water to sanitary sewers during a one inch rain event. This clean water source must be eliminated to prevent sewer backups into basements and sanitary overflows at manholes. Downspouts can be disconnected by cutting the spout, capping or plugging the ground pipe, and installing an elbow and horizontal spout to extend a minimum of five (5) feet away from the home. Flexible downspout elbows can be a relatively easy to install. Costs range from $2-$4 for elbows. Aluminum downspout extensions will range from $4 - $8, depending on length needed. Many options exist for the types of elbows and extensions you may need for your home. Some downspout extensions even roll themselves back up after the rain is done.
Ground
Areas where smoke came through the ground indicate a possible broken private lateral sewer to your home. This smoke can signal a cracked section, root intrusion, misaligned joints, or an offset section of pipe. All of these can lead to collapsing or plugging of your lateral sewer, which would lead to a sanitary back-up into your home. The best way to check the condition of your sanitary sewer lateral would be to have an inspection done by a licensed sewer contractor. These inspections usually include some type of video inspection of the pipe using CCTV (Closed Circuit Television). This will allow the plumber to see exactly where problems exist.
