does anyone know of an approved device that can be installed under the sink that is actually an air gap device?

there is no air gap that is safe to install below sink level. You can install one or more check valves to serve as a backup to the check that is probably in your dishwasher.

QUOTE---"you can install one or more check valves to serve as a backup to the check that is probably in your dishwasher."---INCORRECT --

The plumbing codes strictly prohibit installing any valves on the Drain, Waste & Vent system with the exception of an approved backflow preventer on the discharge of a sump pump or sewage ejector line and under extremely rare conditions you may install a "Backwater Valve" on the house main drain(With the expressed written consent of the AHJ)

If you are under the International Residential Code (IRC) the air gap is not required, however it may be required by your local code.

Under the Uniform Plumbing Code a dishwasher is required to discharge by means of an approved "Indirect waste". The dishwasher inlet port of a garbage disposal is an approved indirect waste receptor. Where there is no disposal you are required to have the air gap, and an air gap is required to be installed above the flood level rim of the sink. In some jurisdictions they require an air gap on all dishwasher whether there is a disposal or not.

Well, if you're gonna start paying attention to code...
Yes it's against code, but if it was a bad idea, then the check valve built into my dishwasher is also bad!

I have an airgap i'd like to get rid off. I'd looked for a johnson tee that I could mount in the wall with the "air" line vented thru the wall to outside. Sounded like a good idea till I ran into the "Visible" requirement in the code.

The extra check valve would have the advantage of being easily removeable in case I ever had to have an inspection.

On the other hand, if you not going to pay attention to code, you have no business giving advice to other in the forum. You should be standing in the aisles at HD with the other wannabee hacks.

The plumbing code does not apply directly to the DW manufacturer.
They have various other rules to follow, and must seek a listing in some cases for the equipment (though not the same as the listing for components of a fixed plumbing system).

That is how (and why) they can get away with check valves and such.
Every DW has an air gap in the supply side above the fill level of the equipment.
They may be as simple as putting the fill half way up the side of the unit.
That, together with the solenoid valve that must open to allow water into the tub, provides the needed safety.

I think the term "get away with check valves" is a little misleading. It implies that the check valve is somehow a less than desireable thing that they have slipped in thru a loophole in the regulations. It's not. It's a simple cheap reliable device that protects the dishwasher from overflowing and flooding due to a backup in the sink. The manufacturer would be criminaly negligent if they didn't put one in. If an airgap is installed, the check is not needed at all.

All of the building codes are written by comittees. They are a combination of mostly experience, a little engineering, some economic influences, and a few myths and misconceptions. They protect consumers from slipshod work and generaly do a fairly good job of that.
However they also protect consumers from technical advances. You get sued for trying anything different, even if it works better.

Codes define one way of doing things. There are other ways of acomplishing the same thing. mostly badly but a few almost as good and maybe some better. But we'll never know!

Every other industry is changing and progressing. But my house is plumbed and wired and built pretty much just like my parents house. Yes I have more bathrooms and my outlets are all grounded, and I have breakers instead of fuses, but that's not much progress in 50 years.

If I can design a better way of doing something, or at least what looks like a better way, I'm going to try it. Wether it's to code or not. I've been burned a few times, and I've had a few "sucesses". If someone else wants to try something not quite to code, as long as they understand exactly what they are giving up and what they are gaining, go for it!

The plumbing code itself frowns on check valves as protection since they invariably become unreliable with time in a sanitary system.
The dishwasher will not have the same level (volume or size) of waste and the use of a check valve for draining becomes a reasonable compromise.
The fact that a DW is not normally 'listed' by a plumbing code organization is exactly why they 'get away' with using the check valve.
Many jurisdictions do NOT believe the check valves are a reliable enough protection and REQUIRE the air gap.

Since air gaps have no moving parts they cannot fail.
If the drain side becomes clogged the discharge water from the DW simply spills out.
The gap between the DW side and the drain side meets the height vs. diameter rules of the plumbing code, and the installation above the flood level of the sink means the DW outlet cannot be submerged if the sink drain should clog.

quertyui - I purchased my current home from someone just like you. Guess what? I'm spending loads of money fixing plumbing and electrical to keep my house from flooding and/or burning down. If you insist on experimenting, at least have the decency to keep detailed records and fully disclose to perspective buyers. If you fail to do so, you could be liable civilly or criminally.

I doubt very much that you purchased your house from someone like me.

The argument might have some validity it there was in fact a check valve in the dishwasher but in fact, in most dishwashers there are no valves for the drain.

Most dishwashers use a two port pump with a reversing motor. When the motor is operated in clockwise rotation the water is pumped to the spray arms. When the pump is operated in reverse, or counter-clockwise, the water goes out the drain line.

The claim that a check valve is a 'Simple, cheap, & reliable" solution it totally false. Check valves work by gravity force and they are notorious for getting gummed up and not working properly, which is why they are prohibited in a drain system.

To say the the codes do not keep pace with innovation is also false. The codes of today are dramatically different from what they were a mere 10 years ago, and we constantly get changes and updates on a quarterly basis.

If someone feels that they have a better solution the proper method would be to test it thoroughly, then submit the design for consideration.

From time to time we see people post solutions that are not code approved. In most cases this is a result of homeowners or DIY'ers who are not familiar with the codes and in those situation we simply try to explain the proper code required solution and the reasoning behind it..On the other hand....
To repeatedly present yourself as a trained professional and give advice that you know is not code approved is unconscionable and in some jurisdictions it is considered a criminal offense.

"Check valves work by gravity force..."

Not true for most DWs.
They are a solenoid actuated spring close valve.

They still can fail though, broken glass and hard seeds are a common cause that get through the pumop can stil get caught in the valve (typcally a plastic ball on the end of the solenoid shaft) and then the valve will fail to close completely.

There are two code-approved ways to put a REAL airgap in without a counter penetration.

One is to put a floor drain in, which would be an approved indirect receptor. Not practical in most homes, but near-universal in commercial kitchens.

The other option, if your sink is on an exterior wall, is a "Johnson Tee". They've been discussed on here a few times before. Basically, it moves the "above the counter" part of the airgap to "outside the house" instead.

"The other option, if your sink is on an exterior wall, is a "Johnson Tee". They've been discussed on here a few times before. Basically, it moves the "above the counter" part of the airgap to "outside the house" instead."

Just watch out for freezing problems.

There is a third option that we sometimes use when a dishwasher is installed on an island where there is no sink, however it requires the expressed written consent of the plumbing inspecting official.

We can install a standpipe similar to those used by a laundry washing machine. With a standpipe the dishwasher drain line must be run up as high as possible under the countertop to form a high loop, then it must drop below the top of the standpipe and turn up to the top of the standpipe.

I was searching for kitchen faucet replacement, and all pics show no air gaps installed next to any faucet, even with a dishwasher present. Go figure.

You know why? Because women usually do the shopping and we care about aesthetics (not that men don't). Stores know this and advertise in a way that is visually appealing.