Basement Flooding After Heavy Rain in Toronto: What to Do First

GTA Plumber Match · Updated October 2026

When a summer storm dumps a month of rain on Toronto in an afternoon, the sewers fill up and water comes back up through basement floor drains. Older homes in the Annex, Leslieville, Riverdale and the Beaches are hit hardest because many don't have a backwater valve.

During the flood

• Stay out of standing water if it could reach outlets, the panel or the furnace.
• Stop using sinks, toilets, the dishwasher and the washing machine. Everything you drain goes to the same pipe that's backing up.
• Take photos and video for your insurer.

Sewage or groundwater?

If water is coming up through the floor drain and it smells, it's sewer backup. If it's seeping through walls or the floor, it's groundwater. The fix is different: a backwater valve for the first, grading, downspouts and a sump pump for the second.

Backwater valves and the City subsidy

A backwater valve lets water leave your house but closes when the sewer backs up. The City of Toronto runs a Basement Flooding Protection Subsidy Program that can cover part of the cost of a backwater valve, a sump pump and disconnecting your downspouts. Check the current rules on the City's website before work starts, since you may need permits and photos.

Call the City first if...

The backup could be in the City's part of the sewer. Toronto asks you to call 311 so they can check the main line.

When you need a plumber to clear the drain, install a valve or replace a sump pump, text us a photo and your postal code. We'll connect you with a licensed, insured, WSIB-covered plumber. Usually same-day, and you get an upfront flat price first.