If you got a notice from the City about dye testing, this page explains why we’re testing homes, what happens during a test and how to confirm a visit is from the City.
Through our Storm Sewer Cross-Connection Investigation Program, we dye-test homes where household wastewater may be entering the storm sewer system because of a cross-connection. Testing is free and takes about 20 to 30 minutes.
Your safety matters to us. If someone comes to your door about dye testing, here’s how to check that the visit is real.
Before testing starts in your neighbourhood, you’ll get a notice from the City.
Anyone visiting about dye testing will:
City staff and our contractors will never:
If you’re not sure, you can ask the visitor to come back another time. Then contact our project manager to confirm that dye testing is happening on your street.
Your neighbourhood has two separate sewer systems:
A cross-connection happens when a home’s wastewater plumbing is connected to the storm sewer instead of the sanitary sewer.
Untreated wastewater entering local creeks and Lake Ontario can harm fish and wildlife, lower water quality and pose risks to public health.
Most cross-connections happened during the original construction of a home or during plumbing renovations. In many cases, homeowners don’t know they have one.
We use specialized cameras to inspect underground storm sewers. When we find signs that wastewater may be entering the storm sewer, we review the camera footage, engineering drawings and other information to narrow down where it’s coming from.
Then we dye-test some homes to help confirm whether there’s a cross-connection and where it is.
We don’t test every home on your street. Getting a notice doesn’t mean we’ve found a problem with your plumbing.
We usually test homes from June to December. Most testing happens in the fall.
During the testing process, you can expect:
The dye is non-toxic, environmentally friendly and safe for household plumbing. It dissolves in water and rinses away easily. If any dye is left behind, staff will clean it up before leaving your home.
If you’re not home when our team visits, we’ll leave a notice at your door explaining how to book your test. To book:
Dye testing is voluntary, and you have the right to decline entry into your home.
We strongly encourage you to take part. Each completed test helps us find cross-connections faster and protect local creeks and Lake Ontario.
The City’s Storm Sewer Use By-law 0046-2022 (PDF) regulates what can go into the storm sewer system to help protect local waterways. Dye testing is one of the ways we find plumbing connected to the wrong sewer and other sources of pollution.
If we can’t find the source and your home is still part of the investigation, we may contact you to ask about testing your home again.
If we find a cross-connection at your home, we’ll contact you to explain what we found and what happens next. The repairs needed, and who pays for them, depend on your home.
In most cases, we’ll arrange and pay for the repair. We usually do the work the following year, in the road in front of your home, to reconnect your sewer pipe to the sanitary sewer.
In rare cases, the work may extend onto part of your driveway or lawn. If so, we’ll talk with you before the work starts and restore any part of your driveway or lawn we dig up, at no cost to you.
We’ll usually give you about two weeks’ notice before construction starts.
Sometimes only certain plumbing fixtures, such as a basement bathroom or laundry drain, are connected to the storm sewer. This can happen when plumbing is changed or added during home renovations.
Who pays for repairs usually depends on whether the plumbing work had the required City permits:
We’ll confirm what work is needed. Costs depend on how your plumbing is set up and how much work there is, so we can’t give a standard cost estimate.
If you have questions about dye testing or a notice you received, contact our project manager or 311:
To book or change a testing appointment, call the field coordinator at the number on your notice.