Backwater valves
Backwater Valve Installation
A backwater valve lets sewage leave the house and stops it coming back in when the sewer surcharges in a heavy storm.
When a heavy storm overloads the municipal sewer, the sewer can push water back up the building drain and out of the lowest opening in the house: the basement floor drain or a basement toilet. A backwater valve sits on the building drain and closes when flow reverses.
What installation involves
The valve goes on the main building drain, in the basement, usually under the floor. That means cutting the slab, installing the valve with an access cover, and restoring the floor. Most Ontario municipalities treat it as plumbing work that needs a permit, so ask your building department and expect an inspection.
What a backwater valve does not do
- It does not stop groundwater. That is the sump pump’s job.
- It does not stop overland water coming in at a window or a door.
- It does not work on a blocked lateral. That is a drain cleaning job.
While the valve is closed
When the valve closes during a storm, the house drains have nowhere to go. Running a washer or a shower during a sewer surcharge fills the basement drain from your own side. Use as little water as possible until the storm passes.
Backwater valve maintenance
Open the access cover once or twice a year, check that the flap moves freely, and clear any debris. A valve stuck open does nothing; a valve stuck closed backs up the house.
Houses on septic
A house on a septic system is not connected to a municipal sewer, so a sewer surcharge cannot reach it. Septic backups have other causes. The well and town water guide covers the rural side.
FAQ
Backwater valves — common questions
Do I need a permit for a backwater valve?
Usually, yes. Most Ontario municipalities treat installing a backwater valve as plumbing work that needs a permit and an inspection. Ask your building department.
Does a backwater valve stop all basement flooding?
No. It stops sewage coming back up the drain. Groundwater needs a sump pump, and overland water needs grading and sealed openings.
How often does a backwater valve need checking?
Once or twice a year. Open the access cover, check the flap moves freely, and clear any debris.
Talk to a Collingwood plumber
Collingwood Plumbers needs three things: the town, whether the house is on town water or a private well, and what the water is doing. Those three decide most of the job, from who you should actually call, to whether the fix is a valve, a pump or a pipe.