dwv check valve

Hilly

Is there a check valve that would work for washing machine standpipe. Is there one that would be suitable for the vertical discharge portion of the standpipe? Would a spring loaded even open? Or is the horizontal portion of the trap arm the only acceptable for a check valve?

icesailor

Washing machime Standpipes:

Clothes washing machine "standpipes" are supposed to act as an indirect waste receptor. Without a "Air Gap" but with the hose installed into the standpipe. The Minimum (I forget) and the maximum, 30" are supposed to let the soap suds and excessive water flow down the pipe. It can't have any check valves in the stand pipe or drain. However, the standpipe can be increased to 2" which will almost always eliminate overflowing of water and soap suds. If the trap is 1 1/2", common in residential applications and the vent is within the proper distance from the outlet of the trap, it shouldn't overflow. If the horizontal run is excessive and it is not fully open, you can get overflowing from the standpipe. Especially if it is too short. I have used 1 1/2" X 2" Bell Increasers to make the standpipe 2" and solved the problem of overflowing. I've even used 3" PVC to stop overflowing. The problem is in the standpipe. A check valve will increase drain friction and make the problem worse. And probably illegal. So is changing the trap size to 2" and connecting it to a 1 1/2" horizontal drain.

On your own, you can do anything you want or what someone might wrongly suggest if it is never going to see the light of an inspector/AHJ. Code wise, enlarge and lengthen the standpipe.

delta T

18"

is the minimum, if I remember rightly. Ice is right. putting a check valve in will cause many more problems than it will solve. If it is accsesible try to find out if ot is vented correctly. If it is vented with a studor vent, make sure you check that it is actually opening. I have had several studor vents stick closed on me causing no end of headache clearing the waste line again and again until I finally smacked the studor vent and everything started draining like a champ. If I am installing I never use less than two inch on a washing machine drain.