I have a 38"standpipe that overflows during drain cycle on my washing machine. I attached a 1 1/2" by 2" rubber coupling and added a 20" PVC pipe extension with. Will the additional height cause water to backup into the washer pump or tub? Is there a check valve in the pump system to keep water from backing up in the washer tub? Can I add a check valve in the drain line? Or should I try another method to keep the standpipe from overflowing? I don't believe there is stoppage in the drain.
Please advise. Thanks.

Code is 48" from bottom of trap.

Hi bcone,

Your drain pipe is clogged and needs to be snaked. That would be the approach I will suggest to you. Adding pipe will maybe stop overflow from standpipe but will not solve your ongoing problem.

But to answer your question: additional height of stand pipe should not cause overflow to your tub or back flow to your washer. However, if the obstruction in drain pipe is past tub drain connection - than yes, you will experience waste water in your bath tub during washer drainage.

Hope that will help... Milo

Codes and pipe sizes differ from area to area...

In my area, an 1.5" drain is all that is required and the standpipe can be between 18-36"... works perfect unless the drain line gets choked down.

As Milo said, your drain line is partially clogged and you can try to snake the drain line to see if that improves things.

If no improvement after snaking the drain then you will be best to cut the drain pipe about 6 inches from where it connects into the earger drain pipe and clean the pipe using a long screwdriver and hammer, basically chiselling the pipe wide open at the larger pipe where these drains are famous for getting choked down. Of course, if the pipe goes down into the floor and you cannot find the connection into the larger drain pipe then you would need to use a larger head on the snake, OK?

We are all glad to discuss in more detail if you want, OK?

Mark

In my area code requires a 3' horizontal line and then change to 2" to the veritcal to 42" from the trap. It also sounds like you have a blockage

As stated above, in my area code only requires an 1.5" waste and vent pipe...so there ya go!

2" pipe is the most commonly recommended pipe size, but it is always a good idea to check code requirements for your specific area when installing any waste/vent piping to a home... ;)

Mark