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Question DetailsAsked on 9/23/2013

Who do I contact to install an air gap in a granite countertop

The dishwasher lacks an air gap and there is a granite countertop that would require cutting a hole in to place the air gap into

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1 Answer


A hole can be drilled through it by a countertop installer, using a carbide or diamond drilll bit - likely to cost about $75-100. Some plumbers also have the drill - up to you if you trust them with thousands of $ worth of granite - I would not.

Several other alternatives, to reduce cost or if your faucet and spray nozzle is not installed through the granite so an air vent there would look funny:

1) installing an air gap just below the countertop next to the sink or in the dishwasher recess next to the dishwasher, just below the countertop - this is less desireable, as it puts moist air under the sink, and also is a bit more likely to overflow if the line gets slightly plugged because it is not as high. Also, the overflow will not go into the sink as a traditional sink-mounted one will, which would make for a wet mess under it, and would violate plumbing code in some jurisdictions. You can use the regular one (more likely to overflow) or here is a picture of an airgap designed into the much larger diameter (so less likely to overflow) drain pipe with provided barb for the drain hose to connect to -

2) if you have a top-mounted sink, install it in a hole drilled in the sink, if there is a place the sink is exposed without granite - just like it normally is with laminate countertop and a stainless sink.

3) run a hole up behind the backsplash in the wall (insulate portion in wall if on outside wall in extreme cold climate where it might freeze) and buy a wall-mount air gap to mount just above the backsplash - looks like this, and the inch or two of tubing leading to it can be concealed in any number of ways - plastic conceal molding or wood trim, etc -

4) in most jurisdictions air gaps are not required, and a "high loop" of the discharge hose can be installed so the hose running from the dishwasher is looped up and fastened just under the countertop then down to the drain with no air gap - article explaining here -

Answered 6 years ago by LCD

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