Primer: the flap that guards the door
Maintaining a Backwater Valve
A backwater valve is a one-way gate in your main drain that closes when the sewer backs up. It only protects you if it can still move freely, and that takes a little attention a few times a year.
- Plain steps you can do yourself, safely
- Clear signs for when to stop and call
- Written for Newmarket houses and water
- A plumber on the phone if it goes sideways
What goes wrong in the pipes
During a severe storm, municipal sewers can surcharge and push water back toward homes. A backwater valve installed on your main drain is designed to close and stop that water entering through basement drains. But debris, grease and sediment can collect on the flap or in the housing, holding it open or sealing it shut. A neglected valve can give a false sense of security.
Have these on hand
- Garden hose or a full bucket
- Flashlight
- Rubber gloves
- Wet vac
Hands-on steps
- Find the access cover. It is usually a round or square cap in the basement floor, often near the front wall where the main drain leaves the house.
- Check the manual. Valves differ by brand. Read the manufacturer's instructions before you open anything.
- Avoid using water. Ask everyone in the house not to run taps, flush or start the washer while the cover is off.
- Open and inspect. Wearing gloves and eye protection, remove the cover and look at the flap. It should be clean and swing freely.
- Clean gently. Remove debris with a gloved hand or soft brush, rinse with a little clean water, and check that the flap seats properly.
- Check the seal. Look at the cover gasket for cracks, then replace the cover securely so sewer gas cannot escape.
Mistakes that turn a small repair big
- Removing the flap permanently. Some people pull the flap after a slow drain. That leaves the house unprotected.
- Using sharp tools. Scraping can damage the flap or seat.
- Pouring grease down drains. Grease is one of the main causes of sticky flaps.
- Skipping the check after a storm. Debris often collects after the valve has done its job.
- Ignoring smells. A sewer odour near the access cover often means a seal is not tight.
When to put the tools down and call
Call if the flap is cracked, stuck, missing, or does not seat properly, or if you cannot open the cover safely. Also call if you have had water backup despite having a valve, since the cause may be a different entry point, like a floor drain connected before the valve. If you do not have a valve yet, ask about installation; check whether a municipal subsidy is available in your area at the time of booking. Call (365) 517-0623 for an inspection. Homes with older drain lines may also need repiping or help with freezing lines; see frozen pipe thawing. For the insurance side of things, read our guide to basement flood insurance.
A well-maintained valve and a working sump pump together make a strong defence against the two most common ways water gets into a basement.
Asked on site
How do I know if I have a backwater valve?
Look for an access cover in the basement floor along the main drain line, often near the front of the house. Your home inspection report may also mention it.
Can I clean it myself?
Yes, many homeowners do, following the manufacturer's instructions. Call a plumber if parts are damaged or the valve is hard to reach.