Flooding: Toronto Gets a Soaking


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In early July 2013, the residents of Toronto, Mississauga, and surrounding areas got a rude awakening: the sewer and drainage systems in their homes, that in many cases had never presented a problem over decades, suddenly failed to carry off flooding water that was falling from the sky faster than the drains could take it away. And like water will do, it found its way to new places: up into people’s basements. As dramatic as the pictures of flooded underpasses and abandoned cars were, the real damage was less visible, and happening below grade.

So, while the roadways generally drained in a few hours, the water that risen into basements was just beginning to do its real damage. Even after it had subsided, basement floors and walls were saturated and furniture and possessions were destroyed. Mould set in, and the curbsides of neighbourhoods were lined with heaps of soaked couches and sodden rolls of carpet.
Many homes found out the hard way that their basement floor drains could work two ways: not only could they take water away from a basement floor, but they could be a conduit for water to enter a basement. Homes that had eavestrough downspouts leading water from their roofs down to drainage systems that ran beneath the basement floors were the worst affected, but even diverting downspouts did not always prevent flooding. If your downspouts were not the source of trouble, your neighbors’ or the municipal sewer might be.
More than rainwater entering through foundations or window wells, this water was quick to appear, and devastating.
So what is the way to prevent this disaster from recurring? People should realize that this “freak storm” might in fact not be a freak but the beginning of a “new normal”. Weather systems are changing, and heavy downpours are a part of that in places like Toronto. Diverting downspouts, sealing basement window wells, and ensuring watertight foundations are all good ideas, but the ultimate response to the threat of basement drain upflows is a drain backup valve.

Summer is Coming: Drain Backup Valves

What is a drain backup valve?

A drain backup valve is a valve that prevents water from backing up against the normal flow direction of the basement drain. When things are operating normally, water and waste flow from their sources into drain pipes, and then to the sewer system. In the circumstance that water is flowing the other way, a drain backup valve will shut, preventing back flow from rising up through the system.


Drain backup valves are typically installed in newly-constructed homes, but Toronto-area houses from before the 1970s did not have drain backup valves installed by default. As a result, they need to be retrofitted to the house’s drain system, a task that should be done by the experts at MasterDrain.

valve diagram

Installing a drain backup valve into an existing system involves breaking the floor slab to access the drain piping at the correct point or points, then removing a section of piping that will be replaced with the drain backup valve. Once the valve is positioned and sealed to the existing pipe, the hole is backfilled and the slab in the work area repoured. Done right, the finished project is unobtrusive, with just an access port showing, flush with the floor.

What are the advantages of a drain backup valve?


A drain backup valve provides the most reliable means of protecting basements against flooding caused by drain backups. This is important, as drain backups are usually the most damaging type of flooding. Not only does the water directly damage the basement and its possessions, but in most cases the water rising in a drain backup is contaminated with sewage, requiring many things to be discarded even if they are not irreparably damaged.

valve dimentions

In addition, many insurance companies are reluctant to insure flood-prone basements, or will require that drain backup protection be installed in order for a homeowner to qualify to re-insure their home. In those cases, a drain backup valve is not only an excellent idea, but a requirement.

Finally, as recent Toronto weather has shown, the chance of such storms and the consequent flooding is greater now than in the past, and a growing risk. Drain backup valves are future-proofing, not just waterproofing, for your basement. To add the protection of a drain backup valve to your home, contact MasterDrain.

Additional details on Emergency Services and Specific Tasks

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