Whirlpool DU890SWKQ has water that backs up into it when we run our washing machine. It is an under the counter unit and connects to the same drain line as the washing machine. The house is older (1966) thus does not have a Drain Air Gap near the sink or anywhere else that I can see. The water remains in the unit thus I have to use the end of a wash cycle to "pump" the water back out of the dishwasher. The unit seems to function well in all other respects.

If you know the problem please give me a good deal of information on how to resolve the issue as I only have the operators manual and not a repair manual.

Thanks,
NCGeorge