If your dishwasher suddenly stops draining and it’s full of dirty water don’t be in a hurry
to replace the unit. Modern simple dishwasher starts at around $350 and sometimes it seems easier to replace the unit then to fix it.

However the problem with drain can be caused by clogged drain channel or
an air gap and even brand new dishwasher won’t drain.

An air gap is a device which prevents dirty water to flow back into your dishwasher. And the air gap is the part which you can clean yourself. It won’t take more than five minutes.

Here are 3 easy steps to check your air gap:
Remove the metal decorative cover cup.
Remove white plastic part in the middle
of the air gap.
Check an air gap tube for debris.

It can be even a corn seed or tiny piece of glass and it would be enough to stop
a dishwasher from draining completely. If you don’t see anything then
the problem with drain is caused by other reason.

And remember- an air gap cap opening supposed to be directed to the sink. Otherwise when the garbage disposal is full water will leak over your cabinets and not to the sink.