Smoke Testing

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Non-toxic smoke testing will be utilized to determine if rainwater is causing excess flows into the wastewater system

Post Date: January 17, 2019

    Hazen and Sawyer, P.C., a local engineering firm, will conduct non-toxic smoke testing in several areas of the City over the next two years. The testing, which is a commonly used procedure, involves blowing non-toxic smoke through pipes to locate defects that would allow stormwater and groundwater to enter the system.

    Prior to testing, crews will post signage and place informational hangers on doors in neighborhoods where the testing will be conducted. The smoke being used is manufactured specifically for this testing procedure and is, therefore, non-toxic, non-staining and leaves no residue. Hazen and Sawyer will utilize clearly marked trucks and uniformed crew members will be onsite and available to answer questions.

    During testing, neighbors may see smoke coming out of storm catch basins or the ground, which could indicate broken manholes, improper connections, damaged or missing clean-out caps, or cracked pipes. Smoke might also be seen coming out of a property’s rooftop vent pipe, which is normal and typically indicates a proper connection to the system.

    This important program will help decrease the inflow and infiltration of stormwater and groundwater into the wastewater system, which will reduce the risk of wastewater overflows in neighborhoods and save money for the unneeded and costly treatment of stormwater and groundwater.

    For more information about smoke testing, neighbors are encouraged to view an educational video produced by the Charleston Water System which is available on YouTube at

    Smoke Testing: Frequently Asked Questions

    What is the purpose of smoke testing?

    The purpose of smoke testing is to find potential points of groundwater/storm water in the sanitary sewer system that could lead to high flows during a storm, heavy rain and King Tide events. Smoke testing can also help locate:

    • Buildings that have downspout, yard or foundation drain connections to the sanitary sewer;
    • Sump pump discharges into a sanitary sewer;
    • Points of groundwater or surface water intrusion into the sanitary sewers;
    • Any cross connections between sanitary and storm sewers.

    What happens during smoke testing?

    The City’s contractor, Hazen and Sawyer, will notify the local fire and police departments where the sewer system smoke testing is conducted. During smoke testing, field crews blow air and smoke into the sanitary sewer system and monitor where smoke escapes the system. Smoke should be visible exiting vent stacks on top of all buildings, which indicates a properly vented plumbing system. If smoke permeates up through a yard, it indicates breaks in the sewer line. If you have any doubt as to the source of the smoke in your home or yard, phone 911 immediately.

    How does smoke testing work?

    Smoke testing forces smoke-filled air through a sanitary sewer line. The smoke under pressure will fill the main line plus any connections and then follow the path of any leak to the ground surface, quickly revealing the source of the problem. Only enough force to overcome atmospheric pressure is required. As long as openings exist for the smoke to follow, smoke tests are effective, regardless of surface type, soil type and depth of lines.

    How may the smoke enter my house?

    There is a potential for smoke to enter a building that has a plumbing fixture that is not properly trapped from the sanitary system. This happens particularly under the following circumstances:

    • The vents connected to your building’s sewer pipes are inadequate, defective or improperly installed;
    • The traps under sinks, tubs, basins, showers and other drains are dry, defective or improperly installed;
    • The pipes, connections or seals in the wastewater drain system in and/or under your building are damaged, defective, have plugs missing or are improperly installed.

    How long will the testing take?

    While crews might be in your area for a few hours, the actual smoke test takes approximately 15 minutes to complete your area of the street.

    What does it mean if smoke enters my house?

    If smoke enters your home during the test, it may mean there are deficiencies in the plumbing that may allow potentially dangerous sewer gas to enter.

    Can smoke plug the sewer?

    There is no way smoke can plug the sewer. The smoke is made up of a vaporized substance.

    What should I do to prepare for smoke testing?

    Door hangers with information will be placed on your front door prior to testing. When you receive notice that smoke testing will take place, you should:

    Check to see that all drain traps under basins, washing facilities and floor drains contain water; simply flush toilets and run or pour approximately two to three cups of water into all drains, including unused fixtures and floor drains;

    If there is an individual in your home or business who has respiratory problems and/or mobility limitations, please call the City’s 24-Hour Neighbor Call Center at 954-828-8000.

    Do I have to be home during testing?

    No. Inspection crews will not need to enter your home.

    I am a pet owner and will not be at home during the testing. Should I be concerned?

    The smoke is not harmful to pets. It would be a good idea to leave several windows partially open for ventilation in addition to turning on bathroom and kitchen exhaust fans. If smoke enters the house, it will dissipate in a few minutes.

    How will I know when testing will occur on my street?

    Door hangers will be distributed at each residence in the area at least 24 hours prior to testing. These will provide information about the procedures, names and phone numbers of personnel to contact for more information.

    What are the benefits of smoke testing?

    Smoke testing is a simple and fast method of testing the sewer system. The smoke is harmless and will disappear after only a few minutes. The testing is also a cost-effective way to find areas of the sewer system that need improvement.

    What should I do if smoke gets into the house?

    • Do not become alarmed;
    • Exit the house and locate the testing Hazen and Sawyer crew working in the area. If they cannot be located, call the City’s 24-Hour Neighbor Call Center at 954-828-8000.
    • If there are any concerns about whether the smoke is due to a fire, call 911;
    • If the smoke appears to be the result of testing work, the testing crew may attempt (at the request of the resident) to locate the defect(s) allowing smoke to enter;
    • Open windows to allow ventilation and note the location of the smoke emission; smoke will clear within a few minutes.

    Is the smoke a hazardous material?

    No, the smoke is:

    • Remember: If the smoke enters your home, ventilate the area to avoid overexposure, which may make you cough or cause irritation. If a household member is overexposed to the smoke, take the individual to an area of fresh air. If breathing becomes difficult, seek medical attention. 

    Can the smoke testing activate smoke alarms?

    Yes, smoke alarms may be activated during smoke testing. Make sure to open windows and/or doors for ventilation.  If you have any questions during smoke testing, please ask the Hazen and Sawyer crew working in the area.  If you are concerned there is a fire, call 911.