Smoke Testing: What Homeowners Need to Know

What is Smoke Testing?

Smoke testing is a widely used method in the industry to identify sources of unwanted groundwater and stormwater that enters the sanitary sewer system. It is important because it reduces sewer overflows, reduces treatment costs, and protects the sewer infrastructure.

A smoke test uses non-toxic smoke and high-capacity blowers to blow smoke through the sanitary sewer pipes. In the image below, a blower is placed on top of a manhole, forcing smoke down into the sewer. If smoke is exiting the ground where there is no connection to the sewer lines, this indicates a place where rain or surface water could enter the sewer system. During a smoke test, a work crew will walk the neighborhood, take pictures of any faults in the system where smoke is coming out of the ground and mark locations for repair.

Common sources of sewer inflow include:

• Roof downspouts
• Uncapped abandoned tap connection
• Leaking maintenance hole
• Cross connected storm drains
• Broken service laterals or mains
• Cross connected sanitary lines
• Cellar drains
• Yard/foundation drains
• Sump pumps

How Should I Prepare for a Smoke Test?

Prior to the testing date, pour half a gallon of water in all basement floor drains or seldom used sink/shower drains. Be sure to flush any seldomly used toilets beforehand. This helps ensure that drain traps are filled with water and the smoke will not enter the home through any normal, working sewer line connections. This process is called “filling your traps.”

Do I Need to Be Home During a Smoke Test?

No, it is not necessary for someone to be home during testing. However, it is not suggested to leave pets unattended in a confined area.

Will Smoke Testing Allow Smoke to Get into the House?

Not if your plumbing is correctly installed and functioning properly.

What Does it Mean if Smoke Enters the Home? How Should I Address it?

If all sewer connections are working properly and there are no plumbing defects in the home, all smoke should run through the sewer lines and out of the building’s roof vents. This is normal.

In the unusual event of smoke entering the home, it may indicate there is a plumbing issue in the home— where sewer gas has been entering the home for months or even years. Sewer gas can be a health hazard.

While the smoke itself is harmless and leaves no residue, it serves only to identify open faults in the home’s plumbing. Once inside the home, the smoke will dissipate in approximately 20-30 minutes. If you notice smoke entering your home, open exterior doors and windows and leave the home until the smoke dissipates to reduce exposure. It is important to immediately notify a member of the smoke testing crew so the fault can be identified and addressed. You should then call a licensed plumber to repair the fault as soon as possible.

Smoke in your home could be an indicator of:

1. The vents connected to your home’s sewer pipes are inadequate, defective or installed.
2. The traps and seals under sinks, showers, tubs, toilets and all other drains are dry, defective or improperly installed.
3. The pipes, connections or seals in the wastewater drainage system or under your home are damaged, defective, missing plugs or are improperly installed.

If the Smoke is Harmless, why is it Recommended to Evacuate the Home?

Evacuating is a precautionary measure in case the smoke is due to a real fire rather than caused because of the sewer testing. Also, because smoke from the sewer testing indicates that dangerous sewer gases are also entering the home. Even though the smoke itself is not toxic—dense smoke or prolonged exposure can be irritating to mucus membranes, so it is always best to minimize exposure. This recommendation extends to pets as well.

How Will I know if the Smoke Enters the Home if I am not There?

The purpose of the smoke test is to identify improper sources of water entering the public portion of the system. While it is also beneficial to identify deficient plumbing connections on private property, it is not the main purpose of the testing. It is the responsibility of the homeowner to maintain the internal plumbing on their private property.

Can the Smoke Test Activate the Smoke Alarms?

Yes, smoke alarms in the home may be activated if smoke enters the home during testing. If this occurs, open windows and exterior doors for ventilation if possible.

What Does it Mean if Smoke is in the Yard or Driveway?

This could indicate that a drain on the property is connected to the sewer lateral or that the lateral has breaks or cracks, causing drain runoff that contributes to sewer backups and overflow.

Is the Smoke Hazardous?

No, the smoke is non-toxic and harmless. It is light in color, leaves no residue and does not create a fire hazard. Anyone with respiratory conditions should avoid exposure to all types of smoke.