Air gap?

Hi all. I am installing a dishwasher (Bosch Singe Dish Drawer) in a kitchen island far FAR from the sink. I want to just drain the dishwasher directly under the floor to a U trap then to an existing drainage pipe from something nearby like from the bathroom (this is all in the crawl space under the house.

The island has no sink (or anything actually) so an air gap would be quite unsightly to say the least.

The instructions assume you will be connecting the drainage line to a disposal and if not gives an alternate approach to using a standing tube and just drape the high loop into the standing tube. Having a standing tube inside the cabinetry open and all, just kind of makes me nervous...

Do I need the air gap? My searches suggest yes, by code. Is there a way to put it under the counter? In my experience, the air gaps always gurgle out some water and I can't have that happening in/under the cabinet...

Any thoughts would be appreciated.

Dane
San Diego

It all comes clear to me now. This is why the studor vent was created...
(throw "studor" into the search feature of this forum)

drain

It has NOTHING to do with a Studor vent, as far as the original question is concerned. ANY open drain for the dishwasher becomes a potential overflow point inside the cabinet. And a sealed drain from the dishwasher to the drain pipe becomes a backflow contamination point if the riser cannot overflow in the cabinet. THEREFORE, you do need an air gap of some kind ABOVE the countertop.

Dane, the California Plumbing Code requires an air gap (807.4). I have never seen them give an exemption for an island, but this is something which can be discussed with the city.

One thing for sure, the p-trap can not be below the floor. And of course the air gap must be above the flood level of the sink.

Honestly, most designers just avoid island sinks when possible, and don't use island dishwashers at all. Any design you wan can be constructed, but you can't just disregard the plumbing code.

Educate me...

Thanks for the input guys. Explain to me if you don't mind talking to a neophyte, why the kitchen sink is the "flood" zone of reference. Let's say my kitchen was on the second floor. Wouldn't any sewerage back flow enter the premises at the lowest outlet say, a first floor bathtub and not even get to the second floor until the house was filled up (asssuming the windows and doors were shut ).

Why does the p -trap have to be above the floor? (apart from code say). If I had a basement it couldn't be just under the floor but still easily accessible and well above the finally drainage point (from a gravity stand point)...

Sorry for the questions but, I am a scientist not a plumber and when someone says you can't do something "that way", I always want to say, "But WHY???"

Dane
San Diego

The air gap has to be above the flood rim of the fixture it is serving. If it was lower than the top of the kitchen sink, then when filled the sink, you would have a problem.

The trap location has to do with total allowed fall ( too much could cause siphoning) .

I know this sees mundane, but the first rule in remodeling is don't tick off the inspector. He makes the rules!

I don't know why people are so upset with something as small as an air gap.

The plumbing code is written to protect health.

For an inspector to look the other way, what happens when he gets sued?

Every City and State will have their plumbing quirks, to be sure.
But in those cities and states, they do have rules, and they must be followed.

A homeowner may not understand what is happening and why it's important.

Hey, when I go to the dentist, I don't understand that either.
I look on the wall, and see the certificates, the licensing, the thank you plaque from the University of Washington, and can assume that he knows what he is doing. My dentist has been teaching at the University for over 30 years, and I've been going to him for 47 years. But do I understand his job?
Oh, heck no!
We both like to ski fast though.

So the sinks in a typical DW installation are the air gap so to so speak Because you and I both know, HJ, that in AZ air gaps are never used for DW. Either they dump into the disposal or a branch tailpiece.

drain

The tailpiece or disposer creates a vacuum break as long as the drain is not plugged and water rises above the connection point. The height of the sink is only a factor when it is in the same proximity as the DW. Otherwise the critical level for the riser/air gap is the lowest opening on the same floor level, which is where an overflow would occur when the system backed up.

Jimbo: Why can't you step it down to interrupt the fall? i.e. an elbow in the vertical pipe and maybe a running trap rather than a p-trap below the floor?

Not trying to pick on you. It's just that you seem to be fairly responsive and sure of what you are saying ... and I also enjoy to hear that something "can't" be done.

Thanks.

Running traps are also not allowed by code.

There are lots of installations which can be done, and in some fashion will work, maybe well, maybe not so well. But there are good reasons behind all codes, and you are wasting your breath trying to convince an inspector for an exception.


Are all codes identical? No. Welcome to America!!!!