Smoke testing is a procedure in which harmless smoke is forced into the sanitary sewer from a manhole. Defects are identified where smoke is found exiting the system either from soil, pavement, sidewalks, storm sewers, cleanouts, or other private drain connections. The defect marks a deficiency in the sanitary system where rainwater or groundwater may enter, leading to possible sanitary sewer overcharge and problems such as overflows and basement backups into people's homes.

The smoke created during the smoke testing procedure is produced by dripping mineral oil onto the heated manifold of a small engine connected to a fan that forces the smoke into the sanitary sewer. The mineral oil is produced by HURCO Technologies, Inc. and is called LiquiSmoke. The smoke has been tested and deemed non-toxic and safe based on the guidelines provided by both the National Institute of Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA). A Material Safety Data Sheet (MSDS) is provided by HURCO Technologies, Inc.

No. People with health problems who cannot leave their house during the smoke testing may request their lateral be plugged to eliminate the possibility of smoke entering their home. Some pet owners choose to remove their pets from the house on the day the smoke testing takes place. Pet owners may also request that their lateral be plugged.

Smoke typically enters the house through an unused drain, such as a basement floor drain, because the trap has dried out, allowing the smoke to push through and enter the house. To prevent or stop the smoke from entering the home, pour some water into the drain to fill the trap. Open ended drain pipes exposed in a house generally due to plumbing work can also allow smoke into the house. To prevent smoke from entering, stick a wet rag into these pipes during the smoke test. Other sources of smoke entry usually indicate a plumbing problem within the house.

Workers may need to access private property to locate and investigate defects identified by smoke testing. Workers may also need to access private property to perform additional testing such as dye tracing of drains suspected of being connected to the sanitary sewer. Workers will not need to enter the home unless asked to do so by the owner, as in cases where smoke is entering the home. In addition, they will not enter an area where animals are fenced in to prevent attack or loss of the animal.

RJN Group has published an FAQ about smoke testing that has additional information.

RJN Group maintains an online list of the areas being tested, along with the schedule and progress.

All customers must follow MSD's Sewer Use Ordinance 8472. The ordinance also allows MSD to require customers to obtain a permit for wastewater discharges. MSD generally limits permits to facilities that fall under federal requirements to obtain a permit:

1. industrial users subject to EPA Categorical Pretreatment Standards,
2. industrial users that discharge an average of 25,000 gallons per day or more of process wastewater,
3. industrial users that contribute a process wastestream which makes up 5 percent or more of the load at a treatment plant,
4. industrial users that have a reasonable potential for adversely affecting District operations or for violating the sewer use ordinance.

In addition, if a customer wants to make a special discharge, either one-time or ongoing that is not part of its routine discharges, MSD generally requires the customer to obtain an Approval for Special Discharge.

You can contact MSD through its Customer Service number, 314-768-6260, 24 hours a day, 7 days a week.

MSD's Sewer Use Ordinance 8472 requires customers to notify MSD of a problem discharge. A problem discharge is defined as:

1. any upset, slug discharge, bypass, spill or accident which does or may result in a discharge into MSD's system or into a watercourse of a prohibited substance as listed in the sewer user ordinance; or of a regulated substance in excess of limitations as listed in the sewer user ordinance;
2. a regulated substance in excess of limitations established in any permit issued to the user by MSD or any NPDES permit issued to the user, and which may: (a) cause interference or pass through; or (b) contribute to a violation of any requirement of MSD's NPDES permit; or (c) cause violation of any State or Federal water quality standard.

For an unanticipated discharge, immediately notify MSD by telephone of the incident and provide the information requested by MSD in order to assess the impact of the incident on MSD's system or on water quality. Within five business days, submit a detailed written report. You will still be liable for any resulting damages, and any fines, criminal or civil penalties, or other liability.

For an anticipated discharge which may cause limits or requirements to be violated, notify MSD prior to commencing the discharge. An anticipated problem discharge will be allowed only when the discharge is unavoidable to prevent loss of life, personal injury or severe property damage; there are no feasible alternatives to the bypass; and advance notice is provided to MSD.

MSD monitors its industrial and certain commercial customers in order to protect the environment, the public, its workers, and the sewer system. This is also required by state and federal regulations. As part of the monitoring program, MSD is required to collect samples of the companies' wastewater discharges, and have them analyzed for pollutants of concern. If a problem is detected, MSD notifies the company so that the problem can be corrected.

You can contact MSD through its Customer Service number, 314-768-6260, 24 hours a day, 7 days a week.

MSD works with community groups on projects to improve water quality, such as stream clean ups or storm drain marking projects.

In most of St. Louis County, the separate storm sewer flows directly to area lakes and stream without any treatment. In MSD's combined sewer areas located in St. Louis City and some of eastern St. Louis County, the sewers drain to a treatment plant. When heavy flows during rain events exceed the capacity of the treatment plant, these sewers overflow into the river.

Contact St. Louis County's Waste Management Hotline at 314-286-9200 for household collection events and waste recycling.