Backwater Valves: How They Work
Picture a flap in the building drain that only opens outward and drops shut when the street sewer surges.
- Step-by-step, written from real jobs
- Tools to have ready and safe stopping points
- Where to stop and hand it to a licensed plumber
- Licensed plumbing trade
- Camera before digging
- Written job notes
- Phone-only booking
Summary card
Picture a flap in the building drain that only opens outward and drops shut when the street sewer surges.
Within the valve housing, a hinged gate lifts as household waste flows out. Should the street main overload and push water the wrong way, the gate drops and blocks it from entering your basement.
Valves must be accessible for cleaning and inspection. With the gate shut, anything you drain upstream has nowhere to go, so limit water use during heavy storms.
The procedure
- Find out whether your home already has one
- Lift the clean-out lid and make sure the gate swings
- Clean debris from the valve body
- Limit water use during severe storms
Tools to have at hand
- Flashlight
- Screwdriver for the access lid
Do it in this order
- 01
Find the access lid in the basement floor
- 02
Open it and look for the flap
- 03
Make sure the flap moves freely
- 04
Clear any debris from the seat
- 05
Close the lid securely
A normally-open backwater valve lets your drains flow out but closes if sewer water tries to come back in.
Whitby Plumbing, from the job
Stop and phone a plumber if
- The flap is stuck
- The valve body is cracked
- Sewage backs up anyway
Notes for Whitby
Installation usually requires a permit in Whitby. Programs to assist homeowners have existed; verify current details.
When the desk should take over
Ring the desk for installation or if the valve is stuck.