Does a washing machine waste pipe need to bend before going in to the U bend?

Ours had a big kink and I have cut it out and dropped the small pipe end straight down in to the U bend.

Paul, August 2009

if you are connecting to the sink u bend, the drain pipe MUST be HIGHER than the u bend, this is to PREVENT BACK SIPHONING DIRTY WATER FROM THE SINK BACK INTO THE WASHER. Best way is a SEPARATE stand pipe due to the BIGGER BORE size being used .

wirecutterman, August 2009