This is how my sink currently looks like. There's this metal cap thing on the right that has slits. It is hooked up to the dishwasher (a brand new Bosch European style one). I have never seen anything come out of it. What is it called? What does it do?


I am doing a complete kitchen remodel and I am wondering whether the new kitchen needs that exhaust thingy. I've been looking at photos of up-to-date kitchens online and I haven't noticed any of them have this contraption. Does that mean this thingy is some outdated technology that I don't need it for my kitchen remodel?

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Yes, you need that - it's plumbing code in most areas. It's an air vent which prevents forming a siphon from the sink into the dishwasher.

The most widely used term seems to be "Air Gap" though you will get better results with "dishwasher air gap"


If you remodeled your kitchen to provide a dedicated, vented in the wall, drain for the dishwasher, you would not need it, as the vent in the wall would serve the same purpose.

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  • Is the wall vent the more modern thing to do? Does that involve drilling a hole all the way to the outside of my home? The dishwasher is in fact adjacent to an outside wall... – JoJo Jan 17 '17 at 0:53
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    No, it's a normal plumbing vent, which typically go up though the wall to the roof. The difference here would be providing a trap, drain and vent for the dishwasher separate from the kitchen sink trap, drain and vent. I'd not exactly be shocked to find that some of the "modern kitchen designs" you are looking at simply haven't actually passed code at the time of photography, or were never real houses; but a dedicated dishwasher drain connection is one safe and legal way to get that "look" if it's important to you. (Or, y'know, that "cup" has no bottom and is how the photographer is hiding it.) – Ecnerwal Jan 17 '17 at 0:58
  • If the kitchen comes equipped with a garbage disposer then it is often possible to use the dishwasher drain tap on the side of the disposer. The internal body of the disposer provides the necessary air gap instead of the separate unit on the counter/sink surface. – Michael Karas Jan 17 '17 at 11:47

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