Inflow and infiltration experts explain how to answer your residents’ questions and ease their fears about the testing process.
With your next inflow and infiltration project, your residents may turn to Google to help them understand the process. Take the opportunity to answer their questions in advance.
SEH inflow and infiltration experts, Kirby Van Note and Lindsey Roberts McKenzie, share some questions you can expect to receive about the smoke testing process and the answers to help residents understand what they’ll see and how to prepare.
To find leaks before they become larger problems. Smoke testing is one of the investigative methods to locate inflow sources in the sanitary sewer collection system. Typically, direct sources of surface water or groundwater can enter the collection system during a rainfall event such as a catch basin, area drains, house roof down spout, sump pump discharge and/or foundation drain directly connected to the sanitary system or storm sewer.
Cities test sewers by putting non-toxic smoke into the sewers to find leaks and faulty connections.
“This method of field investigation is helpful in detecting direct connection points of groundwater or surface water intrusion into the sewer.” Van Note says, “The process is very efficient and cost-effective. It’s a fast procedure compared to other methods.”
Smoke testing involves pushing smoke through the sanitary sewer collecting system, and observing and documenting where the smoke exits. This method for identifying inflow and infiltration typically involves residential, commercial and industrial areas. A blower is set up over a neighborhood manhole and non-toxic smoke is pumped through the sewer line. The exiting smoke can indicate the location of a broken sewer pipe, manholes, catch basins, or where roof or foundation drains are connected to the sewer system. Ultimately, smoke testing helps identify where typically inflow is entering the system.
No. There is nothing to worry about during the testing process. The odorless and colorless simulated smoke will not cause a fire or explosion, and isn’t hazardous or flammable. Simulated smoke is not harmful and should disappear quickly. If you do encounter the simulated smoke – avoid unnecessary exposure to it, long exposure may cause some irritation.
For a single city block, the test lasts about 30 minutes. You may see the simulated smoke coming from manhole covers, storm drains, roof vents or building foundations. As for the duration of an entire smoke testing project that may involve several streets in a neighborhood or an entire community, the engineers conducting the testing develop a schedule based on totality of pipe length and configurations.
Certain locations, like schools, take a bit of extra planning before the process can take place.
“We like to schedule schools during summer, when class isn’t in session,” McKenzie says. “We can also isolate areas to test to see how it impacts the public. It’s very important to have to plan in place before we test a specific area, communicate with residents and isolate the sanitary sewer sections tested to reduce impacts to the residents during the testing.”
“SEH provides all of our own field work, and we have our all of our own equipment, which is very unique for our industry.” McKenzie continued.
Yes! First, notifications should come from your city six weeks in advance before the testing. The notices give a few steps to prepare for the test. For open drain traps, downstairs bathrooms or floor drains, you should pour down a gallon of water to prevent smoke from entering the house. Regardless of the testing, this should be done regularly to relieve the potential of sewer gas entering your home. Two weeks prior to the testing, a public meeting will be held where you can ask questions or voice concerns.
To make sure everyone is aware of the upcoming testing, the teams do some ground work.
“In the days leading up to the actual testing, field crews will walk the neighborhoods and place door hangers.” Van Note said. ”The hangers will have information about the tests, tips to prepare and numbers they can call if they have any questions.”
The smoke is not expected to enter homes or buildings, but if it does, don’t be alarmed—simply open doors and windows to ventilate the area. The simulated smoke should clear out quickly.
The smoke is safe, but long exposure may cause some irritation. The local fire and police departments are involved and notified so they know what’s going on, and know what to say should anyone place an emergency call pertaining to the simulated smoke.
Do NOT be alarmed.
“We recommend residents open their doors and windows to ventilate the premises to clear smoke,” McKenzie suggests. “Simulated smoke will not stain walls or furniture; nor will it leave a residue. If smoke enters a house, it’s best to contact a licensed plumber to find out if you have a sewer connection problem.”
Run water faucets for a few seconds in unused sinks, tubs and drains to fill fixture traps. Pour water into each floor drain (at least 1 gallon). If you have defective plumbing (i.e. no trap), you should consult with a licensed plumber.
The city nor the crew performing the smoke test are required to go into your house if smoke is found in the house, but can if requested by the owner to determine where the smoke is entering the home.
“We can have a conversation, but the most likely outcome is the resident will have to hire a contractor or plumber on their own to fix the issue,” Van Note says.
Start planning in December or earlier to help ensure you are ready to implement the following spring and summer. A substantial amount of prep work and planning is required to implement a successful smoke testing project. The more time and knowledge to prepare, the better.
GIS, or Geographic Information Systems, are used during smoke testing to make better use of city resources with more accurate and accessible data. When you use GIS technology to collect complex data in the field, you can use exiting GIS layers help to build a map book, which helps to build out the schedule for when and where testing can occur. GIS allows a community to prioritize and coordinate future sewer rehabilitation projects. These projects can take place simultaneously with other road improvement or community development programs.
Summertime provides the optimal conditions to receive the best results a smoke test can create. The drier conditions in the summer months lower groundwater conditions allowing the smoke to travel further and provide easier access out of the system.
Work with your consultant or other resources to create information resources in other languages. Consider developing English as a Second Language (ESL) website.
“In the past, we have partnered with the cities to help them develop a website, images and plans to reach their Spanish and Hmong communities,” says McKenzie. “The time spent on developing these additional resources helped their residents where English is a second language be more prepared.”
Clear water or inflow and infiltration from surface water or groundwater sources doesn’t require treatment from a wastewater treatment plant. The extra water in the sanitary system reduces pipe capacity and pipe service, and can produce future operations and maintenance conditions and problems. Ultimately, inflow and infiltration negatively impacts the overall costs of infrastructure over time.
Smoke testing is an efficient and low-cost method of detecting inflow and infiltration. It allows you to understand where problems may exist and gives you time to prepare before they become larger problems.
Additionally, with timely communication with the residents in your community, the project can take place smoothly. From your residents’ perspective, it never hurts to Google.
Kirby Van Note is a water resources engineer and SEH practice center leader that understands the importance of educating the public on municipal operations. Contact Kirby
Lindsey Roberts McKenzie is a water resources engineer and project manager committed to helping cities save money by identifying and resolving inflow and infiltration. Contact Lindsey