# Laundry Backflow Valve



## Jim Nickerson (Mar 10, 2011)

My Laudry is in my basement and the outflow is about a foot higher than the septic line. I attempted to insert a backflow valve in the laundry outflow line, but the flow from the washing machine did not push the backflow valve open causing water to come back. Do I need a vent between the washing machine and the backflow valve?


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## iamrfixit (Jan 30, 2011)

Jim Nickerson said:


> My Laundry is in my basement and the outflow is about a foot higher than the septic line.


This statement is very confusing. Not sure what you are trying to do. 

Rather than a backflow valve; a taller drain standpipe would be a better solution. 

Your washing machine should drain to a 2 inch standpipe with a trap at the bottom. The standpipe must be at least as tall as the top of the normal water level to keep water from draining out of the machine. When it is time for the machine to drain the water is actually pumped out.

Most washing machines can easily pump to an extra tall standpipe if necessary. My washer drain standpipe is almost 6 feet above the floor to prevent sewer backup during heavy rain.


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## the_man (Aug 14, 2010)

is the check valve a swing check or a spring check? is it installed the right way (arrow on the side)?


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## AllanJ (Nov 24, 2007)

The first part of the washer drain (the upright standpipe or riser) needs to be at least 18 inches above its own trap and 2 inches in diameter. And the trap has to tie into the main drain higher than the horizontal part exiting the house. It must be free flowing. The washing machine hose as it came with the machine must be able to reach the drain pipe open end and fit loosely. Don't put a 2 inch check valve in the laundry drain pipe although a larger check valve can exist in the main drain.


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