Basement flooding and backwater valves: Are insurers giving bad advice?

3 August 26, 2014 at 1:36 pm by

As a centre of excellence for basement flood risk reduction, ICLR never advises that just a backwater valve will reduce the risk (indeed, we have 20 tips to reduce basement flooding). Yet Canadian insurers have taken to advising insureds to install a backwater valve or risk having their sewer backup coverage severely sublimited or even cancelled. This has become particularly acute since the Alberta and GTA floods of 2013.

But do insurers really understand what it is they are advising their insureds to do? Do they realize they may actually cause their insured’s basement to flood when it otherwise may not?

Basement flooding is one case where a little knowledge can be dangerous.

A backwater valve is not a silver bullet or panacea, and must be considered in combination with a number of other mitigation measures. Suggesting an insured install a backwater valve but take no other action may give him/her (and the insurer) a false sense of security.

More importantly, where a home’s foundation drain (aka perimeter drain or weeping tiles) is connected to the building’s sanitary sewer connection (as opposed to the storm sewer connection), the installation of a backwater valve on a sanitary lateral without severing the foundation drain and connecting them to a sump or storm connection could cause a basement to flood during a severe rain event. This ‘self flooding’ is caused when the flap of the backwater valve closes during a rain event, trapping water from the foundation drain behind  – or ‘upstream’ – of the valve (keep in mind that while the flap in the valve is closed, the floor drains and weeping tiles in behind the backwater valve are being filled with water from connected downspouts and from showers, dishwashers, etc). This trapped water will have no place to go and, if there is enough of it, it will enter the home’s basement via floor drains or below grade fixtures like sinks, toilets, showers, washing machines and the like.

Though there is no absolute rule of thumb (every municipality, subdivision and home is different), homes built up to and about the mid-1970s that have foundation drainage may have a higher likelihood of having weeping tiles connecting into the sanitary sewer system. It is also possible that homes built after that time have their weeping tiles connected to the sanitary system depending on municipal policies and potential construction errors. Indeed, some municipalities outlawed connection of foundation drainage into sanitary systems in the 1960s, while others allowed this practice to continue into the 1990s.

Currently, there are thousand of homes across Canada that have their weeping tiles connected to the sanitary sewer system, including several that flooded in Burlington, Ontario on May 13 and August 4 of this year.

But regardless of when a home was built, insurers should not blindly advise an insured to install a backwater valve without a plumbing inspection being conducted or without formal communication from the insured outlining with certainty how the home’s weeping tiles are set up. Further, and equally important, an insurer should not advise an insured to install a backwater valve unless they have a good understanding of the specific property and municipal policies related to protection of homes from storm and sanitary sewer backup. Indeed, depending on local wording and interpretation, the National Plumbing Code prohibits the installation of backwater valves in main sewer connections when the sanitary connection serves more than one dwelling unit, as would be the case in a duplex or buildings with basement apartments. (However, in these cases, property owners may be able to install in-line backwater valves.)

Not only is every home different, but a home on one side of a street in a given city may have a completely different foundation drain setup than a home located right across the street or down the road. No two homes are the same and, thus, a blanket policy of installing a backwater valve in order to get sewer backup coverage is not only untenable, it can be downright dangerous. A basement may flood when it otherwise may not, an insured may then have his sewer backup coverage severely sublimited or cancelled because of this bad advice, and the insurer could open itself up to substantial liability and reputation risk.

Along with the advice above, insurers should do two things. They should read the handbook they essentially paid us to write (see our ‘Handbook for reducing basement flooding’) and they should take a page from doctors’ Hippocratic Oath and ‘Do no harm.’



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