This dishwasher was working fine when we moved into this house about a year ago. Now having trouble draining. Old owner's manual suggests clearing the drain air gap, but there isn't one on the sink. It looks like there is only a drain line to the disposal unit. Previous owners had done extensive remodeling in the kitchen. Is it possible for this unit to run properly without a drain air gap? I'm about to pull the drain line out for inspection and cleaning, but I'm baffled by the missing gap.

Thanks! I'm checking the drain lines now.