Why it matters here
During heavy storms, the municipal sewer will fill faster than it drains. When that happens, water finds the lowest opening, and for many houses that means the floor drain in the basement. Fitted in the main drain, a backwater valve closes when water starts flowing back from the street. Oshawa and other Durham municipalities have encouraged homeowners to install them, and many newer homes have one already.
Step by step
- Find out if you have one. Look for a round or rectangular access cover in the basement floor next to the front wall, close to where the sewer exits.
- Open the cover. Inside you will see a clear or removable lid on the valve body.
- Check the flap. It should hang freely, with no debris on the seat.
- Clean gently. Wear gloves. Remove any buildup and rinse with a hose or bucket.
- Close everything securely. Make sure the lid seals so sewer gas cannot escape.
- Repeat twice a year, and after any heavy storm where you suspect it closed.
When a storm warning is issued, minimise water use. A closed valve also keeps your own wastewater in the pipe.
Mistakes to avoid
- Burying the access cover under flooring or storage.
- Removing the flap because it seemed to slow drainage.
- Installing a valve upstream of some fixtures, leaving them unprotected.
- Assuming a valve stops groundwater; that is a sump pump's job.
When to call a plumber
Call if your home has no valve and you have had a backup, or if your existing valve sticks, leaks or cannot be reached. Installation usually requires a permit and cutting the floor. If you are planning work, we can combine valve installation with tankless water heater work or faucet replacement in the same visit. Our guide to plumbing for a basement renovation explains the best time to add one.