Ahoy, mate! Check with your local plumbing codes to see what the specific requirements are for drain hose air gaps in your neck of the woods. In some areas, codes allow looping the dishwasher’s drain hose in a high arc up under the countertop as an alternative to installing an air gap. It’s also worth noting that you can plumb it anyway you want in your own house. The only time the plumbing code is a consideration is if and when you go to sell your house. But as long as you’re doing the work on your own house, you can do whatever you want with your property.

In my au fait opinion, air gaps are over-rated and too often installed when they’re not needed. And, you know, I’ve never seen a dishwasher actually suck water up from the drain hose. Sometimes, I suspect they get installed only to add to the cost of the job (if contracted out) or because the code requirements are not clearly understood.

For example, in a dishwasher that drains into a sink pipe before the p-trap (see Figure 1), the open sink drain serves as the air gap thus eliminating the possibility of getting poopy water sucked back up into your dishwasher. The dishwasher can drain directly into the sink’s trap if you don’t have a disposal. Replace a section of the sink drain’s tailpiece with a dishwasher tailpiece, which has a short T-shape nipple that connects to the dishwasher’s drain hose. Cut the bottom of the sink’s tailpiece with a hacksaw or tubing cutter and connect the new tailpiece with slip nuts and washers.

A common dishwasher drain hose scheme that doesn’t use an air gap is to run the drain hose from the dishwasher’s waste outlet to a tee above the sink’s drain trap or to a dishwasher inlet on a garbage disposal (sealed with a “knockout” plug that’s removed for a dishwasher hookup).

Air gaps aweigh!