Backwater Valve Installation

A backwater valve is a one-way gate fitted to your home’s sewer lateral: wastewater flows out as normal, but when the municipal sewer main surcharges during a heavy storm or rapid spring melt, the valve snaps shut so sewage can’t be forced back up through your basement drains. It’s one of the most effective and most affordable defences against the messiest kind of basement flood. See how it stacks up in our backwater valve vs sump pump guide.

Older, low-lying and combined-sewer neighbourhoods across Ottawa are the most prone to sewer surcharge. That backed-up water is contaminated, far worse to clean up than ordinary groundwater seepage. We install the valve in an accessible pit with a clear, removable cover so it can be inspected and cleaned. We also handle the plumbing permit and inspection this work requires.

A backwater valve works best as part of a layered defence: the valve blocks water coming back through the sewer, while a sump pump and interior drainage manage groundwater around the foundation. During a free inspection we’ll tell you honestly whether a valve on its own is enough, then point you to any rebates you qualify for. The City of Ottawa’s Residential Protective Plumbing Program offers up to $1,000 toward an interior backwater valve (and refunds the building-permit fee) for eligible homes.

What this fixes

• Sewage backing up through floor drains in heavy rain
• Homes on older or combined municipal sewers
• Basements that sit below the level of the street sewer
• Layered flood protection alongside a sump pump

Wondering about price? Try our cost calculator or read ourHow Much Does Basement Waterproofing Cost in Ottawa? (2026 Guide).