Thursday, 7 June 2012

Backwater valves

Basement flooding can be caused by a number of reasons including cracks or leaks in basement walls, blocked pipes, failure of foundation drains (weeping tiles) and poor lot drainage. Heavy rain events can also overload city sewer systems and lead to sewage backing up through house sewer lines and flowing into unprotected basements. Damage from sewer backups is costly for homeowners and municipalities. The Canadian insurance industry pays an estimated $1.7 billion each year in claims due to water damage. 

A backwater valve is a flood-proofing device that prevents sewage in an overloaded public sewer system from backing up into your basement. This fixture, placed on a sewer line in your basement, works as a one way system - sewage can go out, but not back in. The backwater valve automatically closes if sewage backs up from the main sewer line. You should contact a licensed plumber to install a mainline backwater valve and to obtain the proper plumbing permits.

Backwater valve (source:
Since decades ago, the National Plumbing Code has required the installation of a backwater valve. In HRM, construction or renovation projects have been required to follow the National Plumbing Code including the installation of backwater valves. This became more closely monitored after HRM amalgamation in 1996, when all of HRM required inspections with the issuance of a permit for construction or renovation projects.

Today you are required to get a construction permit (and inspection) for any renovation or construction exceeding $5,000 or when performing structural work. This would include adding or altering a connection to the storm or ssystem such as installing a backwater valve (the only exemption is when replaceing a plumbing fixture).

For more tips on reducing the risk of basement flooding, check out this brochure and video provided by the Insurance Bureau of Canada.


  1. My fiance and I just bought a house and our basement floods every time it rains. We had someone that does basement waterproofing in New Jersey come out and he out a french drain in but it was still flooding. Then he came back out last week and put a sump pump in. Hopefully this works.

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