I attempted to use our dishwasher to clean a greasy, soot-covered
barbeque pan (a bad idea, by the way). The dishwasher stopped, with a
blocked outflow indication. I opened it, used a wet vac to drain it,
and cleaned out the internal filters, sump pump, and anti-backflow
valve. This got the water circulating inside again, but it still
wouldn't drain.

Turns out, enough crud had pumped up to clog the air gap. (The air gap
is an anti-siphon device, often a small chrome cylinder by the sink.)
Once I opened that up and cleaned it, everything was flowing like
normal again.

Here's some more information about air gaps:
http://www.popularmechanics.com/home...c/1275531.html

Larry Lang