Q&A OF THE WEEK: “Should I install a backwater valve in my basement?’

Read on to learn about protecting your home against catastrophic sewage backup through your basement floor drain.

Q: Is it a good idea to install a backwater valve to protect my basement from sewage backup? I live in Ottawa, Canada and I’m considering this upgrade.

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A: The short answer is “probably yes”. A backwater valve is a one-way sewage device that’s a great upgrade for most homes connected to a municipal sewage system. It’s installed in the main outgoing sewage line from your house (typically running under the concrete basement floor), and it allows sewage to only flow out of your home, not back in. Depending on the design of the municipal system you’re connected to, and your location relative to the height of surrounding land, a failure of the municipal system during times of heavy rain could allow thousands of gallons of raw sewage from other homes into your basement. Most often this happens in the basement where the main floor drain is located, but sewage can back up and spill out in other places, too. Many homeowner insurance packages include coverage for this sort of damage, but you’re much better off never having to make a claim like this in the first place.

The drawing below shows a typical water valve in both open and closing positions:


Installing a backwater valve requires access to the main drain pipe as it exits the basement floor. This involves breaking up the concrete in a small area around the pipe as it sits below your basement, then cutting this pipe and installing the backwater valve so all sewage flows through it, then on out. If the flow of sewage is reversed because of a flood condition, then the backwater valve kicks in, preventing the sewage from entering your home. It’s fairly easy to replace the concrete after the backwater valve is installed, too.  Is all this a hassle? Yes, but it’s a small price to pay to prevent the kind of sewage disaster that affects thousands of homes every year.

Want to learn more about how backwater valves are incorporated into basements, and how basement drain systems work? Click below for a video tutorial on basement drains in general, including backwater valves. It’s part of my homeowner course on finishing basements the right way.

See what they’re saying about this course:

“One of the best things I did is sign up for Mr. Maxwell’s basement renovation & finishing course. Facing a fairly complicated affair with my laundry room, I wanted to pick up some pointers about how to plan and execute the feat of doing the job myself and, even if I hired a professional to do it for me, how to deal with a contractor. Not only is the course. Not only is the course itself a super learning experience, but Steve is available to answer questions.”

– KC – Kanata, Ontario

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