Plumbing notes · before storm season
The one-way flap that keeps the street’s sewage outside
When a summer downpour overloads the municipal sanitary sewer, sewage can push back up your lateral and up through the basement grate, the lowest way out it can find. A backwater valve is a hinged flap in the building drain that swings shut when flow turns around, and it ranks among the strongest single defences against that particular mess.
The mechanism
Inside the body is a buoyant flap that normally hangs open, letting wastewater run out to the road. When water tries to come back, the flap floats up against its seat and seals. A clear cover on top lets you see the flap and lift it for cleaning.
Where it is set
It goes into the building drain inside the basement, downstream of the fixtures it protects, which usually means cutting the slab. The layout is planned so the grate and low fixtures sit on the protected side. Oakville generally requires a permit and inspection.
Living with one
- Peek under the cover each spring and fall and nudge the flap
- Clear any grit sitting on the seat
- Hold off on laundry and baths until the storm passes and the flap reopens
- Keep fat out of the drains, since it can foul the flap
- Keep storage boxes off the cover
Programs and paperwork
The Region’s flood-prevention program has, in past years, covered a slice of what these valves cost, along with sumps and downspout work. Amounts and eligibility change, so read the Region’s current terms before booking, and keep receipts and photographs.
Read next
- Draining heater sedimentonce a year
- Slow drainswhenever a sink lingers
- Lead and galvanized pipeswhen buying an older home
- Backwater valve installationstops sewer flowing back in
- Basement floor drain backupswater rising from the floor drain
Questions about your own house? Call (365) 517-8536.