Backwater Valve Basics for Lethbridge Basements

How it works

The valve sits in the main sewer line inside the house. Wastewater flows out normally, but a flap closes if water tries to flow back in from the main.

Do you have one?

Look for an access cover in the basement floor, often near the floor drain or the front wall where the sewer leaves the house. Your home inspection report may also mention it.

Keep it working

Remove the cover once or twice a year and check that the flap moves freely and nothing is caught in it. Keep the cover clear of flooring and storage.

When the valve is closed

While the valve is closed during a backup, avoid running water in the house. With the valve shut, your own wastewater has nowhere to go.

Adding one

Installing a backwater valve usually needs a permit. The plumber can check whether your sewer layout suits one; see sewer lines and backwater valves.

Other ways to protect a basement

Keep floor drain traps filled with water, have the sewer line camera-inspected if drains often back up, and make sure downspouts carry water well away from the foundation.

Check your insurance

Some home insurance policies cover sewer backup only as an add-on, and some ask whether you have a backwater valve. It's worth asking your insurer what your policy includes and whether a valve changes your coverage or rate.

Normally open or normally closed

Some backwater valves stay open and only close during a backup; others stay closed and open only when water flows out. Each type has its own maintenance needs. Ask the plumber which kind you have and how to check it.

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