I have a 10 year old house with (probably) 2" vertical waste line inside the wall (plastic at top). Lately we've noticed suds foaming out of the drain at the end of the rinse/spin cycle. It does NOT leak when the machine is pumped out, only at the end of the cycle. We have a 10 year old Amana top-loading washer, and are using the recommended amount of Purex liquid detergent. The washer has a corrugated flexible drain hose, with 1 1/8" diameter end that fits 5" into the waste pipe.
I tried to snake the waste line but the snake will not make the bend at the bottom of the wall (about 3-3.5'). I also tried a clean-out that is about 1' from the drain line (the snake went in a good 15' and came out clean). I suppose the cleanout is in the vent line, upstream of the drain line.
It seems the drain takes the water (both wash & rinse) but then fills up with suds at the end of the spin cycle. Other than reducing the amount of detergent, is there anything we can do?