Fog testing to identify sanitary sewer improvements

November 16, 2017

Fog testing to identify sanitary sewer improvements

Utilities Kingston will conduct sanitary sewer work in the Reddendale and surrounding area, beginning on November 21. This proactive work helps us locate breaks, defects and potentially inappropriate connections to the local sanitary sewer system. It is part of our efforts to maintain the sewer system and help prevent basement flooding.

The work is being completed through our contractor D.M. Robichaud & Associates Ltd (“No Dig”). A detailed map of the work area is available below. 

As part of this effort, crews will conduct fog and dye testing to evaluate both the municipal and the privately-owned infrastructure. Fog testing will take place first and, if inconclusive, may be followed by dye testing into January. 

What's involved with fog testing

Fog testing involves temporarily isolating a part of the sewer and forcing white fog in through a maintenance hole. Fog will then escape the sewer system. Any improper connections identified (such as cross-connections to the storm sewer system, major cracks in piping, improperly connected downspouts and foundation drains, as well as incorrectly plumbed features in a home) can then be followed up with. 

During testing, any fog coming from sewer vent stacks on houses or holes in the ground is NON-TOXIC, NON-STAINING, ODOURLESS, WHITE TO GREY IN COLOUR, and will not cause any FIRE HAZARD.

Some fogs sources are normal and to be expected. Some are not normal and will be investigated to determine if and how they are letting groundwater or stormwater into the sanitary sewer, thereby reducing sewermain and pumping station capacity for wastewater collection. 

What to expect if you're in the work area

Utilities Kingston will hand-deliver advanced notices to impacted homeowners, which will explain what to expect and how to prepare for fog testing. It may be necessary for No Dig to go door-to-door and residents are encouraged to ask for identification. 

To prepare for testing, please do the following as soon as you receive a hand-delivered notice: 

  • If there is an individual in your home or business who has respiratory problems or is a person with a disability, please contact the contractor’s project 
    co-ordinator, as described below. 
  • Run several litres of water from each indoor faucet or shower. 
  • Pour several litres of water into all other drains, such as lesser-used showers and floor drains.

This will ensure that all of the traps in your home’s plumbing are full of water and will prevent entry of any fog into your home through dry traps.

What to expect: 

  • In most cases, the only place fog will be visible on your property is where it emits from your home’s plumbing ventilation stack. This is normal.
  • If you have dry traps, improper plumbing or illegally-connected drainage features, you may see the fog coming out elsewhere.
  • If fog gets into the house, then open windows, turn on exhaust fans and note the location of the fog. The fog will dissipate in a few minutes.
  • If there is fog in your home, please contact us as described below, so we can document the location and the source of the fog.
  • If the fog test alone is inconclusive to identify any breaks, leaks or improper connections, then the inspection crew may perform a dye test.
  • To do this, staff will request permission to come onto your property. A dye test entails pouring dyed water into a fog source and monitoring the sanitary sewer on the street to confirm whether or not that is where it goes.
  • If a fog source in your home is noted, staff may ask your permission to enter your home to conduct a dye test.
  • Please ask for Utilities Kingston or contractor identification before allowing anyone to enter your home.


In the event of a related emergency or sewer spill, or fog, contact the contractor’s project co-ordinator at 613-410-3265. Alternatively, contact a Utilities Kingston inspector at 613-532-3048 or our 24-hour line at 613-546-1181. 

Project area map

To request this map in a larger format, email 

Project area for fog and dye testing is bound by •	Sunny Acres Road to west of Old Front Road, and Henderson Boulevard, south to Lake Ontario.