Basement Flooding and Sewer Backup in Toronto: Causes, Fixes and the City Subsidy

Work out which kind of flooding you have

Sewer backup arrives from below: the floor drain, a basement toilet or a laundry standpipe, usually during or just after heavy rain, and it smells like sewage. Toronto’s older neighbourhoods south of Eglinton still sit on combined sewers that carry stormwater and sanitary flow in one pipe, and a big storm can push that pipe above the level of your basement. Groundwater or surface water arrives through the walls, at the cove joint where wall meets floor, or over the sill of a window well, and it is usually clear or muddy rather than foul.

A failed private lateral looks like chronic slow drains, gurgling and backups in dry weather. Cast-iron and clay pipe from before 1970 cracks, sags and fills with roots, and the repair is on your side of the property line. Photograph where the water first appeared and when, because the answer determines whether you are calling a plumber, a waterproofer or 311.

Who is responsible for which pipe

In Toronto the property owner owns and maintains the sanitary and storm laterals from the house to the property line. The City is responsible for the section between the property line and the main under the street. If a plumber’s camera shows the blockage or break is on the City side, the call goes to 311 and the City investigates; if it is on your side, the repair is yours, and the City will not pay for it even when the pipe is old.

Ask any drain contractor for the camera recording and a locate that marks where the problem sits relative to the property line. A clear video is also what your insurer wants if you make a sewer backup claim, and it prevents paying to dig up a pipe that turns out to be the City’s.

What the fixes actually do, and what the City subsidizes

A backwater valve is a one-way flap on your sanitary lateral that closes when the sewer surcharges, so sewage cannot flow back into the house. While it is closed nothing in the house drains either, which is why the plumber will tell you not to run water during a storm. A sump pump with a pit collects groundwater from the foundation drain and pumps it outside, and severing and capping the foundation drain from the sanitary sewer stops groundwater from loading the City system in the first place.

Toronto’s Basement Flooding Protection Subsidy Program contributes toward exactly those items: a backwater valve, a sump pump, and disconnection of the foundation drain, with conditions that the work is done by a licensed plumber under a City plumbing permit and that the application is made after the work is complete. Downspout disconnection is mandatory in Toronto and is not subsidized, but it is often the cheapest single improvement. Read the current program page before signing a quote, because the eligible amounts and rules change.

• Camera inspection recording and locate
• City plumbing permit number for the valve
• Licensed plumber’s invoice with itemized parts
• Photos of the finished installation
• Subsidy application submitted after completion

Insurance, condos and what not to do

Sewer backup coverage is usually an add-on to a Toronto home policy, and overland water is a separate add-on again. Check both before a storm, not after. Insurers commonly ask whether a backwater valve is installed, and some price the premium on it.

In a condominium, the lateral and the risers are usually common elements and the corporation’s responsibility, while a flooded locker or in-suite finishes may be yours. Report to property management before hiring anyone. Whatever the building, do not stand in water that could be in contact with electrical outlets, and do not run the washing machine or dishwasher while the sewer is surcharged.