Public Works: Floodproofing

When Water Attacks: A Homeowner's Guide to Floodproofing

Part I : Flooding
Part II : Basement problems
Part II.a : Basement Protection Berm
Part III.a : Sewer Backup Prevention - Floor Drain Plug
Part III.b : Sewer Backup Prevention - Standpipe
Part III.c : Sewer Backup Prevention - Overhead Sewer

Part III.d : Sewer Backup Prevention - Backup Valve

Sewer Backup Prevention - Backup Valve
A backup valve stops the water in the sewer pipes. Older versions of the approach were located in the basement and relied on gravity to close the valve. If debris got caught in the flapper, the valve did not close tight. Because of its unreliability, valves were discouraged and even prohibited in some communities.

A newer "balanced valve" has corrected these design shortcomings. A system of counterweights keeps it open all the time so debris won't catch and clog it. When the sewer backs up, instead of relying on gravity, floats force the valve closed. It is usually installed in a manhole in the yard so there is less disruption during construction and no concerns over breaking the pipes under the basement floor.

As with overhead sewers, a valve is fully automatic. It can even work when there is surface flooding. The owner can still use the sanitary sewers during flooding as long as there is power to run the ejector pump, which forces wastewater into the sewer line when the valve is closed.

Precautions
The ejector pump and the valve require maintenance. This work requires a licensed plumber and a permit from your building department.

The cost of this type of backup valve is comparable to the cost of an overhead sewer, in the $3,000-$5,000 range.

Part IV : Insurance