We live in a rural area. Most people send the drain water from the washing machine out to their septic tank or a french drain.
Our problem: when our washing machine drains a second time in a cycle - the waste water backs up out of the stand pipe.
The stand pipe is 2" in diameter, reduces at a 90 degree angle to 1 1/2" - 2' below the washer.
Then it's 1 1/2" in diameter out to the yard for about 50'.
The washing machine is vented in common with the toilet, sink, bathtub.
Any help is appreciated. I'm thumped.