during the wash and rinse cycles water drains at about half normal draining velocity. this causes too little water to complet the wash and rinse cycles. at the end of the wash and rinse cycles, normal draining volume is observed. what is causing the water to drain out during the wash and rinse cycles. this happens about half of the time, not always but the washing action is impaired and is no longer reliable. whirlpool MODEL# DU800CWDB5

Glad you got an expert to reply, but the service manual he posted does not look anything like your dish washer. I am no expert but I would check your collector and make sure there is nothing preventing the check ball from closing off the drain hose. Being inconsistent makes me think there is something down around the check ball that sometimes stops it from sealing off the drain. To drain your motor simply runs in reverse and forces the ball up to seal off the water from going back up into the basin and forces it out the drain hose. I may be wrong but I have been looking at a very similar dishwasher for a few days and have decided that is how it drains. Just my 2 cents anyways.