Pictured is the setup I've had on my LG washing machine for the last 8+ years, I've never had an issue with it. Laundry drain pipe goes up to about 7 feet (installation manual says drain pipe can go max 96" from bottom of washer) then into a standpipe that is about 27" from the bottom of the P trap, then ties into the kitchen drain from the 1st floor and straight to the sewer line. I have an AAV as a vent, I believe it should be a bit higher but the ceiling doesn't allow. Otherwise there is no access to a vent as it's in the basement. It's a LG washer from about 10 years ago (model WM2650HWA).
Anyway, as noted I never had issues with this setup. Just recently I installed pedestals under the washer which raises it 12". Ever since then the washer backs through the drain pipe, if I run the kitchen sink at the same time it backs up so bad that it comes out of the washing machine. Note, if I do not run the kitchen sink it just backs up into the washing machine itself and doesn't completely empty. I'm not sure if either the setup isn't right, or if I need to adjust the discharge and/or standpipe heights. I thought of just putting in a check valve (both to the kitchen and washer), but not sure if that's just a band aid on a problem. Any help would be appreciated.
Anyway, as noted I never had issues with this setup. Just recently I installed pedestals under the washer which raises it 12". Ever since then the washer backs through the drain pipe, if I run the kitchen sink at the same time it backs up so bad that it comes out of the washing machine. Note, if I do not run the kitchen sink it just backs up into the washing machine itself and doesn't completely empty. I'm not sure if either the setup isn't right, or if I need to adjust the discharge and/or standpipe heights. I thought of just putting in a check valve (both to the kitchen and washer), but not sure if that's just a band aid on a problem. Any help would be appreciated.
