Toronto & the GTA

Backwater valves

A valve on the building drain, so a backup in the city sewer is less likely to come up through the basement floor.

Call (289) 901-4881 Request service
A rusty sewer cover set in green grass

Why basements flood from the sewer side

During heavy rain, the city sewer can fill faster than it drains. When that happens, water and sewage can push back up the pipe that connects your house to the sewer, and come out at the lowest opening in the house, usually the basement floor drain.

A backwater valve sits on the main building drain. Normally it stays open and the house drains as usual. When flow reverses, a flap closes and holds the sewer back.

For a finished basement, it’s one of the most effective protections there is. In Toronto, installation usually needs a plumbing permit and inspection, and the City’s subsidy program has its own requirements, so check those before work starts.

How it works

One flap between your basement and the city sewer

A backwater valve sits on the main building drain and only closes when the flow reverses.

On a normal day the backwater valve's flap hangs open and water from the house flows through it to the city sewer under the street. Flap open, house drainsCity sewer
Normal day. On a normal day the flap hangs open and water from the house flows through the valve to the city sewer.
During a storm the city sewer is full. Sewage pushes back up the pipe toward the house, and the backwater valve's flap swings shut and holds it back, so the basement stays dry. Sewer backs upFlap closesBasement stays dry
Storm. During a storm the city sewer is full. Sewage pushes back up the pipe toward the house, and the flap swings shut and holds it back.

While the flap is closed, water from the house can’t leave either, so keep water use low during a storm.

What we do

How a visit goes

  1. Call

    Tell us about the basement and any past backups.

  2. Assess

    The main drain is located and checked to see where a valve can go.

  3. Install or service

    The valve is installed, or an existing one is cleaned and checked.

  4. Show you how it works

    You’ll know where it is, what it does, and how to keep it working.

What homeowners say

5.0 from 41 reviews on Google.

Questions homeowners ask

Do I need a backwater valve?

If your basement is finished, has a floor drain, and your area has had sewer backups during storms, a backwater valve is strongly worth considering.

Can I use water in the house when the valve is closed?

Use as little as possible. While the valve is closed, water from the house can’t leave either, so heavy use during a storm can back up inside the house.

Does a backwater valve need maintenance?

Yes. The flap and housing should be checked and cleaned periodically so debris doesn’t stop it closing.

Is there a subsidy in Toronto?

The City of Toronto’s Basement Flooding Protection Subsidy Program has covered backwater valves, with conditions such as permits. Check the City’s program page for current details before work starts.

Where we work

Homes across Toronto, North York and York Region.

Toronto

North York

York Region

All service areas · Based in North York, working across Toronto and the GTA.

Call, or leave a number.

The phone is the fastest way in. For a same-day visit, or a 24/7 emergency, call Mayan Plumbing. If you’d rather we call you, leave a name, a number, and what’s going on.

Phone
(289) 901-4881
Email
mayanplumbers@gmail.com
Service area
Toronto and the GTA, including North York, Thornhill, Vaughan, and Richmond Hill.