I am not a plumber....... Air gap
To prevent wastewater from draining or siphoning back into the dishwasher, many local codes require that the appliance be connected to an air-gap fixture before the disposal. The air gap, bought separately, mounts on top of the sink or counter right next to the sink and connects to two flexible hoses—one that runs to the dishwasher’s drain and another one that runs to the sink’s trap or the dishwasher inlet on the disposal. 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. Check your local B.D.
If your sink doesn’t have an unused hole for mounting the air gap, you’ll need to bore one in the countertop next to the sink using an electric drill and a hole saw or have the sink top drilled. I think there is a drain piece with that adpt. built-in, a real plumber should be along shortly. Be safe, GBAR
If an air gap is required by local code, it must be installed above the overflow level of the sink. As noted, you can bore a hole to install it. If you can get away with looping the dishwasher drain hose, that's all done inside the base cabinet.
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