Dye Testing


Sewer (storm or sanitary) connectivity of various sewer system drainage features (catch basins, downspouts, drains, laterals etc) can make a difference in flood reduction strategy.

Sanitary sewer smoke testing is an economic and efficient way to find suspected sources of unwanted inflow & infiltration of rain water into sanitary sewer systems. The more smoke that is seen the more certain a direct connection exists between the source and the sewer system being tested.

Dye Testing is an efficient methodology to test and confirm the connectivity of suspect catch basins (as flagged during smoke testing).

This Toronto City-Wide Project, is concerned with confirming the connectivity of storm sewer catch basins that were found and documented as connected (a source of I/I) to the sanitary sewer system through smoke testing. These identified storm system catch basins are being dye tested to further confirm the unwanted connection of the catch basin to the sanitary sewer.

Once the suspected connection (through smoke testing) is confirmed through dye testing, rehabilitation work will be designed and completed in order to disconnect the catch basin from the sanitary sewer and properly connect it to the storm sewer system.

Post rehabilitation smoke testing (more economic) or dye testing if carried out, would then confirm that the rehabilitation work (connection of the catch basin to the storm sewer and disconnection from the sanitary sewer) was successful.

TQI developed an apparatus that allows us to rapidly introduce dyed water directly into a catch basin lead to test its connectivity. Dyed water is injected and flushed down the catch basin lead with water. Observers stationed at downstream sanitary and storm manholes, observe where the injected dye appears. Photos are taken and the connection is documented. When suspect inlets are close together, we utilize different colours of dye and proceed upstream along a sewer line when testing.

The dye being used is environmentally friendly and not harmful to people or the waterways.

Dye Test Examples

Street Catch Basin - Correctly connected to Storm Sewer

Street Catch Basin - Incorrectly connected to Sanitary Sewer

Reverse Grade Driveway Drain - Incorrectly connected to Sanitary Sewer

Dye Testing FAQ

When a catch basin is connected to a sanitary sewer instead of a storm sewer, it is a major contributor of unwanted flow (rainwater) in the sanitary sewer system potentially contributing to sanitary sewer backup & flooding during rain storms. Dye Testing is a method used to further confirm the suspected connection of the catch basin to the sanitary sewer. Once confirmed, measures can be put in place (under another project) to connect the catch basin to the correct storm sewer.

Catch Basins on the street right-of-way that are suspected of being connected to the sanitary sewer (through the smoke testing exercise) are being dye tested to confirm this connection.

There will be no effect on residents and their homes from this activity. TQI is only testing suspected catch basins on the public right-of-way.

The various coloured water tracing and leak detection Dyes that TQI will be using are environmentally friendly, biodegradable and resistant to absorption and is certified for use in drinking water. The Tracer Dye is not harmful to people or the waterways (fish etc). The dye contains no pollutants as per the Clean Water Act. The Dye is a way to trace where the water flows from one point to another.