So question (homeowner, not a plumber) - I redid my counters and a new dishwasher, didn't put an air gap in - I routed the dishwasher drain to the disposal, and it loops way up behind the sink and then to the disposal entry. It's secured with zip ties, no issues for 17 years - so is that a "high loop"? (Well, only issue has been coffee grounds in the disposal getting flung up into the drain port and clogging it a bit, but I spoke to the Mrs. about that...)