Smoke Testing: What Homeowners Need to Know

What is a Smoke Test?

Smoke testing is way of identifying sources of surface inflow to the sanitary sewer, which can negatively impact our local wastewater treatment plants.  A smoke test uses non-toxic smoke and high-capacity blowers to blow smoke through the sanitary sewer lines. Watch the "Work We Do" video below to see our crews performing smoke testing in a local neighborhood:

What happens during a Smoke Test?

The diagram below shows how a blower is placed on top of a manhole, forcing smoke down into the public sewer system.  If smoke is exiting the ground where there should be 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 walks the neighborhood to check for deficiencies in the system where smoke is coming out of the ground, and marks the locations where repairs are needed.  Because your private plumbing is directly connected to the public sewer system, it is important for you to be prepared.

Common sources of sewer infiltration include:

• Roof downspouts
• Unconnected sewer lines
• Abandoned sewer lines
• Leaking manholes
• Cross connected storm drains
• Broken sewer laterals or main lines
• Cross connected sanitary lines
• Yard / foundation drains
• Sump pumps

Smoke testing helps your community identify these deficiencies, helping to stop overflows and reduce wastewater treatment costs.

How should I prepare for a Smoke Test?

Prior to testing date, pour ½ gallon of water in seldom used sink/shower drains and be sure to flush any seldom used toilets.  This ensures drain traps are filled with water and smoke will not enter the house through any normal, working sewer-line connections.

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. People with particular respiratory sensitivity should avoid exposure to all types of smoke.

Do I need to be home during a Smoke Test?

No, homeowners do not need to be home during testing. 

How will I know if smoke enters my house if I am not home during testing?

The purpose of a sewer smoke test is to identify improper sources of water entering the public sewer system, such as from roof or yard drains. The smoke testing may also identify deficient plumbing connections on private property, though this is not the main intent of the testing. It is the responsibility of the homeowner to maintain the plumbing on their private property and private sewer lateral.

Will smoke testing the sewers allow smoke to get into my house?

If your plumbing is correctly installed and functioning properly, and your traps are all filled with water, then no smoke should enter your home.

What does it mean if smoke is in my house? What should I do?

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

The unusual event of smoke entering the home means there is an open deficiency or break in the private plumbing, where sewer gas has been entering the home for some time, possibly months or years. This sewer gas is poisonous and highly dangerous to residents, while the smoke is harmless and leaves no residue—it serves only to identify open deficiencies in the private plumbing. Once inside the house, the smoke will dissipate in approximately 20 – 30 minutes. If you notice smoke entering your home, you should open doors and windows and leave the house until the smoke dissipates in order to reduce exposure. It is important to immediately notify a member of Vallecitos' smoke testing crew working in your area so the deficiency can be identified and addressed. Vallecitos is not responsible for correcting deficiencies to the private sewer lateral within the public right-of-way or any piping on private property. You should call a licensed plumber and repair the deficiency as soon as possible.

Smoke in your house could be indicating:

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

If the smoke is harmless, why is it recommended to evacuate the building?

This is a precautionary measure in case the smoke is due to a real fire rather than the sewer testing, and also because smoke from the sewer testing indicates dangerous sewer gasses are also entering the home. Although the testing smoke is not toxic, dense smoke or prolonged exposure can be irritating to mucus membranes, so it is always best to minimize exposure.

Can the smoke test activate the smoke alarms?

Yes, smoke alarms may be activated by testing. Open windows or doors for ventilation if possible.

What does it mean if smoke is in my yard or driveway?

This could mean a drain on the property is connected to the private sewer lateral or the lateral has breaks or cracks in the pipe, causing drain runoff to contribute to sewer backups and overflows and increasing treatment costs by adding unnecessary flow to the public sewer system.