We have had to re-route our washing machine drain because of a cracked
line under the slab. Our new lines have about a 6 inch fall from the
washing machine drain pipe, then a pee trap. When the water pumps out
of our machine the water is backing up out of the pipe. When we
finished, we put a hose in the pipe and turned it on and had no
problem with the water draining. What have we done wrong? Thank you
for your replies.