Quick Answer: A backwater valve stops sewage from backing up into your basement through the floor drain when the City sewer overloads. A sump pump removes groundwater that collects around your foundation. If your basement has flooded from the floor drain, start with a backwater valve; if water seeps in through walls or the floor, you need a sump pump, and many older Toronto homes are best protected by both.
Homeowners often ask us which one to buy, as if the two were competing products. They are not. Each one solves a different problem, and choosing the wrong one leaves the real cause of your flooding untouched.
What a Backwater Valve Does
A backwater valve is installed on the main sewer line under your basement floor. Normally it stays open, so wastewater from your home flows out to the City sewer. During a heavy storm, when the sewer under the street fills and starts to push back, the valve closes and stops that water from coming up through your floor drain, toilet or basement shower.
Choose a backwater valve if:
- Your basement has flooded through the floor drain, especially with dirty or smelly water
- Flooding happened during a major rainstorm, when your neighbours flooded too
- Your house is connected to a sewer that has backed up before on your street
What a Sump Pump Does
A sump pump sits in a pit in the lowest part of your basement floor. The weeping tiles around your foundation carry groundwater to the pit, and the pump lifts it out of the house and away from the foundation. It deals with water from the ground, not from the sewer.
Choose a sump pump if:
- Water seeps in where the walls meet the floor, or through cracks in the slab
- Your basement gets damp or wet after snowmelt or long periods of rain
- Your weeping tiles are being disconnected from the City sewer, and the water needs somewhere else to go
When You Need Both
In many older Toronto homes, the weeping tiles were originally connected to the sewer line. That means groundwater and sewer backup can arrive through the same pipe. While the weeping tiles still connect to the sewer, a surcharging sewer can push water back into them around your foundation, so the plumber has to account for where the weeping tile connects.
The usual solution is to sever and cap the weeping tile connection to the sewer, send the weeping tiles to a new sump pit, and install a backwater valve on the sewer line. The result is two separate paths: groundwater is pumped out, and the sewer can no longer push back in. A camera inspection of the line under your floor shows us where the weeping tile ties in before any concrete is cut.
What the City of Toronto Subsidy Covers
The City of Toronto's Basement Flooding Protection Subsidy Program pays up to 80 per cent of the invoiced cost of eligible work, up to a program-wide maximum of $6,650 per property for work completed on or after November 12, 2025. The individual limits are:
- Backwater valve and alarm: up to $1,600 per device, on up to two devices
- Sump pump and alarm: up to $2,250 for one device
- Sump pump battery backup: up to $300
- Weeping tile severance and capping: up to $400
A backwater valve claim needs a building permit and a City inspection, and the valve must not be covered before that inspection is complete. Subsidies are paid by the City on a first-come, first-served basis, so confirm current amounts on the City's page before you start. Our Toronto basement flooding subsidy guide walks through each step of the claim.
How to Decide for Your Home
Start with where the water came from the last time your basement got wet:
- Through the floor drain or toilet during a storm: backwater valve.
- Through the walls or slab, or after snowmelt: sump pump.
- Both, or you are not sure: have the sewer line camera-inspected and get a combined quote.
If you have never had water in the basement, a plumbing assessment is a sensible first step, and the City subsidizes that too.
Book a Basement Flood Protection Assessment
Advanced Plumbing & Drains has installed sump pumps and backwater valves in Toronto homes since 2005, from High Park and The Junction to East York. We handle the permit, book the City inspection, and give you the itemized invoice your subsidy application needs.
See our sump pump installation service, or call (416) 769-8800 to book. Same-day appointments are available.