Smoke testing is one of the simplest non-invasive testing methods to detect sanitary and storm sewer line defects and blockages, pinpoint potential inflow and infiltration (I/I) points, and discover illegal (illicit) sewer tie-ins. It is a good way to know “something” is wrong, but further investigation is often required to know what that something is.
The vast majority of U.S. cities struggle to locate I/I areas, but identifying them is critical to the health of sanitary and storm sewer infrastructure, soils, and ground water. The most common areas to find I/I include uncapped sewer clean-outs, improperly connected sump pumps, improperly connected downspouts, and illegal tie-ins.
62.5% of them are private lines.
What is an Illegal Tie-In?
An illegal tie-in occurs when a private sewer drain line is tied into an existing lateral line of the wrong sewer type. Illicit tie-ins can occur via downspouts or sump pumps, but can also include illegally tied septic systems, and even regular toilet drains. In most cases the facility or homeowner would have no idea their tie-in was illicit because they’re often mistakes made by contractors who failed to identify which sewer line they were tying into.
Unfortunately, those mistakes can put entire communities, and their freshwater and groundwater sources, at risk. One such example occurred in Martha’s Vineyard in 2021. The town of Tinsbury suffered a complete wastewater system failure due to the illegal sewer tie-in on a nearby property. Low elevation levels and flooding at the property in question caused their illegally tied-in sump pump to dump into Tinsbury’s main sewage treatment facility, overwhelming it and causing “hundreds of gallons of sewage to be discharged into the Vineyard Haven harbor as a malodorous stink lingered for hours,” according to the Vineyard Gazette.
That “malodorous stink” is one way many municipal managers first hear of, or smell, an illegal tie-in. That’s because toilets or septic tanks dumping into storm sewers can quickly be discovered by everyone nearby, or at the location where the storm sewer exits ground, be it at a treatment plant or a body of water. Repairing an illegal tie-in is usually the home or facility owner’s responsibility, once it is identified, so it can be helpful for owners to identify all their private and public line tie-ins, so they know they’ve got it right.
The processes to mitigate an illicit tie-in varies from community to community and state to state, so it is important for the property owners to check their local municipality’s ordinances and requirements. That said, most often the remediation requires that the illegal connection be disconnected and connected to the proper sewer line.
The Three-Step Smoke Testing Process
For the municipal or large campus water and wastewater manager, finding defects, pinpointing inflow and infiltration, and locating illegal tie-ins is why they smoke test. It’s easy, ecologically friendly, and efficient.
The smoke testing process can be broken down into just three simple steps: Locate Insertion Point, Deployment, and Tracking/Reporting
Locate Insertion Point – When deploying smoke cartridges (sometimes still also referred to as candles, although smoke candles are rarely used today), you need a way into the sewer lines. While the way in can be through a manhole, the type of blower used can determine the size of the opening/entrance needed. A clean-out can also be used as an insertion point.
There are two varieties of blowers that can be deployed in a sewer smoke test: A squirrel cage and a direct drive propeller blower. These names refer to the type of fan each uses to blow the smoke. The squirrel cage is usually the larger of the two and provides more static pressure, while the propeller-style blower offers greater cfm (cubic feet per minute) capacity.
Deployment/Release – Affix a blower that contains a smoke cartridge securely to the sewer entry. It’s important that the blower fan apparatus (if over a manhole) or blower tubing (if over a smaller opening) be as airtight as possible, so that the smoke is forced through the sewer line and doesn’t escape before you can trace it.
The smoke itself is non-toxic, usually formulated from mineral oil, and dissipates quickly.
Tracking/Reporting – Release the smoke into the sewer line and track it to where it escapes. A properly tied-in and maintained system will show smoke escaping from other manhole covers and the plumbing vents for buildings legally tied into the system via private lateral sewer lines.
If you track smoke coming up from the ground or through cracks in the pavement, that’s a sure sign of a sewer defect and infiltration risk. If smoke tracks to a cleanout, chances are good you need to replace a cracked cleanout cap. If you see smoke releasing from, say, a residential gutter or downspout, that’s a sign of an illicit tie-in that could impact your wastewater system.
Communication is Key: How to Message Before Testing
As a municipal or large facility/campus manager, there are two simple steps you can take to make sure your smoke test doesn’t cause undue distress to residents.
- Notify the Community/Neighborhood/Facility – You can do this via paper notices, email, press releases, and/or on your website. It’s important to explain what you’re doing, when you’re doing it, what the residents may see, and reassure them that the smoke is non-toxic and will quickly clear. Your notice should also advise them to fill all plumbing p-traps prior to testing to limit the smoke they may encounter.
- Notify Emergency Services – Police and Fire departments must be notified and coordinated with so there is no confusion that a smoke test could be mistaken for an emergency situation.
Creating a plan for your smoke tests and executing them in small test areas throughout your community or campus can give you the quickest snapshot of where your sewer lines are at risk.
For a complete map of your subsurface sanitary and storm sewer lines, you can hire a private sewer scope company, like GPRS, to provide you with NASSCO-certified video pipe inspection reports that can detail every blockage and pipe defect, and can even include a full inclination report so you know what’s happening in your mainlines and laterals without expensive excavation. GPRS Video Pipe Inspection Services also provide smoke testing and dye tracing services, nationwide.
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Frequently Asked Questions
What is the difference between a public and private sewer line?
Generally speaking, a public line runs only on public property, so a main public sewer line would run under a street, for example. A private line would be the sewer lateral that extends from that main line to a home or other building. It is a common misconception among residents of any community that the lines that leave their homes and connect to the sewer main is part of the public system. But in fact, 65% of all utility lines of all types are actually private, not public. Learn more about the difference between private and public utilities, here.
How often should I have my wastewater infrastructure inspected and mapped?
GPRS recommends that large campuses, facilities, and municipalities conduct regularly scheduled annual sewer scope inspections to provide updated existing conditions data on tie-ins, cross bores, blockages, cracks, and other defects. Building a library of NASSCO reports can help you to better plan and maintain your sewer mainlines and laterals to prevent inflow and infiltration, and soil and groundwater contamination.
GPRS sponsors Water & Sewer Damage Awareness Week (WSDAW). This national event is October 21-25, 2024, and brings water and wastewater safety experts to your community or facility to show you how to mitigate risks to your water infrastructure. Learn more about WSDAW, here.
