Here's the situation: bought a new dishwasher 4 years ago (I think). Lately it has failed to drain the wash compartment after a wash cycle -- there's always about an inch of water in there. If I push the "drain" button a few times, it empties out a little at a time. So it's not clogged -- it just drains slowly. I have checked the drain hose (I can blow air through it into the disposal fine). I tried plunging the drain in the compartment, too. Nothing came out.