Smoke Testing




2 crew members working near a manholeSmoke testing is a process used by Hendersonville Water & Sewer to identify issues with the sewer system. Non-toxic smoke is blown into manholes and crews observe areas where smoke escapes identifying broken manholes, cracked lines and illegal connections. 

Smoke Testing FAQ

Pruebas de Humo Preguntas Frecuentes

What is the purpose of smoke testing?

The purpose of smoke testing is to find potential points of inflow and infiltration in the public portion of the sanitary sewer system. Smoke testing is a cost-effective way to locate issues in the system. It can also help locate buildings that have downspout or basement drains, cross-connections between sanitary sewers and storm drains, and defective sewer connections that could allow sewer gases into a building.

How does this process work?

Crews use a blower to force air and artificially produced, non-toxic, white smoke through a blocked off section of the sanitary sewer system. Smoke should escape from neighboring manholes and building roof vents. Smoke escaping through the ground or cracks in the street indicates there are defects in the line where rain or groundwater can enter the system. Crews take note of where they see smoke escaping so that areas can be further inspected and repaired.

house diagram showing sewer connections

How will I know when Hendersonville Water & Sewer is doing this work in my area?

Hendersonville Water & Sewer will notify customers of scheduled work using their notification system. The phone numbers and email addresses in the system are generated from the information customers provided when they enrolled in water service. It is important that customers provide current contact information to receive notifications. If you need to update your phone number or email address, please call customer service at (828) 697-3052 Monday-Friday from 8am-5pm.

Will smoke enter my home or building?

drain trapProbably not. If your plumbing is properly connected, has no defects and all the drain traps are properly sealed, no smoke should enter your home. If drain traps are dry and have not been used recently or if your plumbing is defective/improperly installed, smoke may enter. You can minimize the chances of this happening by adding water to drains and fixtures prior to testing.

What should I do if smoke gets into the house?

Open the windows to allow ventilation and note the location of where the smoke is entering the building. Exit the building and notify city personnel in the area. If you have any doubts about the origin of the smoke, exit the building and dial 911.

Is the smoke hazardous?

No. The smoke used during the testing is not harmful to you, your pets, food, or house plants. It will not stain clothes or furniture. It is not flammable and does not create a fire hazard. While the smoke is not considered harmful, it is recommended to avoid prolonged periods of exposure.

If the smoke is not harmful, why do you recommend evacuating the structure?

We recommend evacuating as a precautionary measure in case the smoke is due to a real fire rather than the testing. Also, if smoke enters your house during testing, this can indicate other sewer gases may also be entering the building.

Can the smoke testing activate the smoke alarm?

Yes. Smoke alarms may be activated during smoke testing. If you have any doubts about the origin of the smoke, exit the building and dial 911.


Questions may be directed to Hendersonville Water & Sewer at (828) 697-3073 Monday-Friday 8am-5pm. Issues occurring outside of regular business hours can be reported to the after-hours number at (828) 891-7779.

Scheduled Smoke Testing:

Planned Smoke Test