Toronto Backwater ValvesAs unsettled weather patterns continue to drop unprecedented amounts of precipitation on widespread regions of the Toronto, officials urge homeowners to consider installing backflow valves.

A good way to protect against sewage backups is to install backflow valves, which are designed to block flow into the house.

Valves vary in complexity, tightness of their seals and ease of operation.  For example, gate valves are backflow valve backwater valve generally complex and require you to be there at the time of crisis to operate them by hand, but they supply a very tight seal.  Flap or check valves, which allow flow out of the house and close automatically when flow reverses, are simpler.  Our award-winning Mainline check-valve design offers an exceptionally tight seal when compared to a gate valve and still requires periodic testing, but they protect you automatically, even if you are not at home!

Many municipal Building Codes require you to have a backwater valve if your plumbing fixtures are below the top of the first upstream manhole on your street.  A properly operating backwater valve allows flow to only go in one direction (out), preventing wastewater from entering your building during regular sewer system maintenance or accidental sewer system backups.  To find out if you have or need a backwater valve, check your plumbing plans or consult with your builder or a professional plumber.  Remember, if sewage backs up into your home, the cost to repair damages and clean up the mess will be well higher than the cost to install a valve.  Laws allow that towns and municipalities cannot be held liable for damages when a backwater valve has not been installed by a property owner.  Truly, “an ounce of prevention is worth a pound of cure!”

The following should be kept in mind when installing backflow valves:

  • Local codes and ordinances regarding backflow valves must be carefully checked to avoid having to tear out and replace with an approved valve.
  • Changes to home plumbing must be done by licensed plumbers or contractors, who will ensure that the work is done correctly and according to all applicable codes.  Costs are likely to range from a few to several hundred dollars.
  • Some valves incorporate the advantages of both gate and flap valves into a single design.  Plumbers and contractors can provide advice on the relative advantages and disadvantages of the various types of backflow valves.
  • Valves should be installed on all pipes that leave the house or that are connected to equipment that is below the potential flood level.  So valves may be needed on washing machine drain lines, laundry sinks, fuel oil lines, rain downspouts, and sump pumps, as well as sewer/septic connections.
  • Sump pumps are sometimes connected to underground drain lines, which may be difficult to seal off.

Do I Need a Backwater Valve ?

Some Toronto homeowners live in flood prone areas.  One of the keys to building a flood proof basement is knowing your location in relation to the sanitary sewer system that serves your building or home.  A sewer backup valve (waste backwater valve) can make the difference between having your basement flooded knee deep with raw sewage and staying high and dry.


  • Home #1 Does not need a backwater valve because water would drain from the first upstream sanitary sewer manhole which is lower than the inlet to the drain pipe in this home’s basement.  This home should never experience a flooded basement due to a sewer backup.
  • Drains located on the first floor of Home #2 might be safe as it is slightly higher (must be at least 24″ higher) than the first upstream sanitary sewer manhole cover, but there are some cases in which pressure builds enough to temporarily allow water to flow at a level above the lowest drain.  When in doubt, and especially when the second floor living space is installed, it is wise to install a back water valve.  However, any drain fixture in the basement of Home #2 would be below the level of the first upstream manhole and sewage backups could occur without a backwater valve.
  • Any drain opening in Home #3 would be located below the level of the first upstream sewer manhole cover so this home would definitely require the installation of a backwater valve.


Some building codes now require the installation of a backwater valve no matter where the home is located in relationship to the first upstream manhole cover.  Please check local municipalities plumbing code or with your local building inspector.

Backwater Valve Features

  • Toronto Fullport Mainline backwater valveMainline Model #4963 A (ABS) & Model #4963 P (PVC) full port backwater valves.
  • Clear Top for easy visual inspection.
  • Fullport (normally open) non flow-restricting design.  It’s virtually self-cleaning!
  • No problems with Blockages.
  • Gate closes automatically when sewer starts to back up
  • Built in main sewer cleanout.
  • Cleaning rods do not destroy the gate when feeding or retrieving cleanout cables.
  • Normally open design allows the free circulation of air throughout the plumbing system to the municipal sewer system.
  • New, Award-Winning Technology.
  • Affordable building drain backup protection.
  • Backwater Valve US Patent #5406972
  • Backwater Valve Dimensions: Width: 10″ (254 mm), Length: 15.5″ (394 mm), Height: 11″ (280 mm).

How to install your backwater valve

A backwater valve may fail to protect if there is a back-grade (flat or negative slope) through the valve.  In order to achieve a minimum slope of 2% through the valve in a retrofit installation, the installer will most likely need to expose up to 4 or 5 feet of pipe.

Many sewers are flat or back-graded and additionally, there is a 3/4″ difference in height from inlet to outlet on a Mainline Fullport Backwater Valve.  It may be necessary to adjust the grade on the piping leading up to the valve to achieve the required slope through the backwater valve.

With widespread record rainfall across the Toronto, and with widespread development that over-burdens the capacity of municipal sanitary sewer systems, basement flooding is occurring at record levels.  Many officials are urging Toronto homeowners to install backflow valves and are changing new construction code requirements to incorporate backflow valves in sewer lines between the home and street.

“Fullport Backwater Valves” are designed to be installed on the inside of a home or building in the basement floor.  In some installations, predominantly when the home is build on a concrete slab or above a crawlspace, it is not possible to install a backflow prevention valve on the inside of the building.  The Mainline “Adapt-A-Valve” is designed as an economical valve to be installed outdoors in the ground.


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Mister Plumber in Toronto, ON specializing sewer repair, upgrade waterline, lead pipe replacement, water service upgrade, drain cleaning, backwater valve installation, lead pipe replacement, re-piping and emergency plumbing, Mister Plumber uses the latest technology to effectively troubleshoot and quickly repair any plumbing problem and offers a fast response and free estimates. Call us 416 939 1530 or fill the form for Online Free Estimate.

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