Fog Testing in the Madawaska SPS Catchment Area

The Regional Municipality of Durham is working with Civica Infrastructure on an Inflow and Infiltration (I/I) Reduction study. The study’s objectives are to identify sources of rainwater entering the sanitary sewers and develop a plan to reduce these flows.

The sanitary sewer system is an underground pipe network that collects wastewater produced by houses, businesses and industries. The purpose of the pipe network is to direct the wastewater to a treatment plant where the water is treated before being discharged into Lake Ontario. Wastewater is the water that has been used by the community and disposed of including any water that enters the sanitary sewers from toilets, sinks, showers and other appliances.

I/I occurs when water enters the sanitary sewers through undesired connections such as roof downspouts. The rainwater and groundwater reduce the capacity of the sanitary pipe network and the treatment plant. This also increases the risk of overloading the pipe network and potential basement flooding.

In order to identify sources of I/I, Civica Infrastructure, with support from the Region, will be conducting a sewer fog testing program in the Madawaska Catchment Area throughout the period of April 7 to April 18, 2025 between the hours of 9 a.m. to 6 p.m. Fog testing is a safe and easy way to locate potential sources of I/I in the system.

What is fog testing?
The fog test consists of blowing a harmless colored vapour into the sewer manholes and pipes and observing where the fog exits from the system. The fog is expected to exit primarily out of manholes on the street and the sewer plumbing stack at the top of your house. It is also possible for fog to exit stormwater catch basins and roof downspouts at the side of a house. The fog used in the test has no odour, isn’t harmful to your health, and will disappear after a few minutes. During the fog testing, Civica Infrastructure staff will complete a quick walk around your property to mark all the locations where fog is exiting the sewer system. Staff will not need to enter your house to conduct the fog test at any time.

What do you need to do and what notices will you receive?
Fog testing will occur in your neighbourhood in the next one (1) to two (2) weeks. You will receive an orange door hanger notice (one to five business days before testing in your immediate area. When you have received the door hanger, pour one pail of water (approximately five to six litres) into any infrequently used sinks, showers and bathtubs, as well as your basement floor drain. The basement floor drain is typically a small, perforated metal plate located on your basement floor. It is usually located near a low spot in the basement floor close to the furnace or laundry room.

You do not need to be home for the fog testing, but you can be home while the test is occurring.

For contact information, the fog testing area map and frequently asked questions, please visit the
Fog Testing in the Madawaska SPS Catchment Area PDF.