I have a 2" PVC standpipe that is 33" tall. It feeds into a 2" P trap (cast-iron) connected to a 2" T. The top of the T is the vent pipe, and the bottom is connected to the sewer line. Using a garden hose, I can open it at max, with no overflow. I ran a snake into the cast-iron P trap (and as far as we could get it in--probably the T) and found no visible grease, debris or other blockages. When my washer drains, however, the PVC overflows (after some time of draining). When we stop the water being pumped out of the washer, the water drains. It just does not take the water at full flow coming from the washer. Our initial thought was that we did not have enough drain capacity, but we have read other posts that suggest that 2" standpipe and 2" line is sufficient. Any suggestions what might be wrong and how to fix it (other than a new sewer line)? (My washer specifies I need a 17 gpm drain.)

There is a long discussion of this at https://www.askmehelpdesk.com/showthread.php?t=10656

Rather than buy a new washer, I would suggest sealing it as Tom suggested. Use a reducer on the 2'' PVC if you need to to get down to the coupling he suggested.