Product review (5 stars): Dishwasher not draining reliably
I had a problem with our KitchenAid dishwasher not reliably draining. Sometimes it would drain. Sometimes it would not drain.  I replaced both drain hoses and the drain pump. Both of these did not enable the dishwasher to drain every time. Replacing the check valve seems to have fully resolved the problem. Perhaps the stiffness of the valve increases over time, decreasing the drainage flow.