Hi all, I have a very peculiar setup. I have an under-the-sink space-saver dishwasher but when it drains, water shoots out of the airgap into the sink. After that initial spurt, the next time the dishwasher tries to drain, the sink drain actually floods up (just lower than level with basin) and water dribbles out of the airgap. That behavior continues for the rest of the times the dishwasher drains throughout its cycle.

After running the dishwasher, the sink doesn't drain well (it bubbles when draining) until I blow on the airgap (using a handy paper-towel roll as a "straw"). When I blow into the airgap, water shoots up out from the sink's drain. After that water comes up, then the sink drains fine again--at least until I run the dishwasher again.

As long as there is no water in the air gap discharge, the sink drains just fine. I've attached a photo of the plumbing with the dishwasher pulled out.

Name:  UnderSink.jpg
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BLACK HOSE: Air gap discharge
White Ribbed Hose: Dishwasher discharge
Silver Hose: Cold water inlet to Dishwasher

I had a handyman who told me to remove the air gap and have the dishwasher discharge directly into the p-trap (which was previously hidden behind the drywall). He said this would cost $90 to fix.

I then had a master plumber, who told me the only solution is to remove our silestone counter, remove both cabinets to the right of the washer, and tear open the drywall because all of the plumbing lines need to be redone. He wanted to move the p-trap to the left of the dishwasher (to make it accessible) and change the height of the horizontal line through the drywall until it reaches the vent about 2-4 feet away (there is a window directly above the washer). (Is this setup called a "dirty arm"?) This was thousands of dollars.

My question: would the handyman's simple answer fix my problem? Is the present installation not up to code--hence the reason for the major reconstruction from the master plumber? Does anyone have input for my situation?