My washing machine, because of where I have to place it, has an extension on the drain hose. On nearly every wash, it overflows BEFORE it proceeds to drain normally. It usually dumps about a pint or two of water on the floor in the laundry room at the start of a rinsing/draining cycle, then after it does that it drains normally for the remainder of the cycle.
Any suggestions or ideas as to what the problem is?
Thanks a bunch--
Muskman

What size is the standpipe? How high is it? and is the trap vented?

I guess my standpipe (it projects upward and outward from the wall behind the washer) is about 40" high. To the best of my knowledge, it is probably not vented.

Has the drain always overflowed or did it just start overflowing?