I am remodeling my kitchen; pretty much all of the work except for installing a granite countertop. I am putting in a dishwasher (kitchen previously did not have one) and I would prefer to install an air gap whether or not the local codes require it. However, of the models I looked at on-line, only one discussed mounting support, and it couldn't be mounted on material thicker than 1.25". The countertop people will drill any holes I need for the faucet, etc., I just need to know how to actually fasten one of these things to a 2" thick surface. Any advice on brands that might be made especially for this, or any tricks for extending the fastenings that come with air gaps?


To install faucets or air gaps in thick countertops, simply bore a wide hole (2 1/2 - 3 inches) from the bottom of the countertop halfway through or so. In your case, they'd have to bore a wide hole at least 3/4 inches up from the bottom. The hole just needs to be wide enough to provide room to secure the nut.

In concrete countertops, the forms are made with holes pre-cast wide at the bottom and narrow at the top.

  • What tool would be best used to accomplish this on a plywood underlayment? Some kind of rotary tool? What if there is already a hole there and you just need to recess it a little bit on the bottom? (Hypothetical question) why don't they just make air gaps with an extra inch of threads? – FGreg Dec 30 '17 at 17:51
  • My question seems to have an answer elsewhere: diy.stackexchange.com/q/48957/74858 – FGreg Dec 30 '17 at 18:38

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