Our dishwasher works and drains fine when it's running a cycle. :D
When it is off, however, and the sink faucet is on and running water, the dishwasher fills up . :eek:

It seems as if the sink is draining at least partially into the dishwasher. :(

Any ideas? :confused:



KLT

Look for a check valve in the drain line from the dishwasher to the sink drain line. It is there to prevent this from happening. It might be sticking open. Tapping on the valve may temporarily alleviate this situation but replacement will be your final cure.

It is improperly installed DishWasher discharge line. Your DW drain line should have High Point instead sloping directly, and backwords, from sink drain (or disposer ) towards your DW. Create a hight loop, attach to the bottom of your countertop.

This is a good example why UPC requires Air Gaps...

I agree with Milo it sounds like improperly plumbed, see the images below with Air Gap and high looped with out Air Gap, Thanks.

John