Thread: Air Gaps. I'm Confused.

IRC P2902.3.1 "The minimum required air gap shall be twice the diameter of the effective opening of the outlet, but in no case less than the values specified in Table P2902.3.1"

Table P2902.3.1 lists values in inches "Away from wall" and "Close to Wall"

What's up with this??? Shouldn't Table P2902.3.1 be listing values that are distances from potable outlets to flood rim or receptors. What does distance "from or close to walls" have to do with anything as it relates to backflow? I assume the meaning of a receptor is synonomous with an overflow drain.

By the way-I notice you guys posting excepts from codes into threads. This must mean that you have them in electonic format. Where do you get these"? IRC, Florida Codes. And how much are they?

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Originally Posted by Tom McDonnell

IRC P2902.3.1 "The minimum required air gap shall be twice the diameter of the effective opening of the outlet, but in no case less than the values specified in Table P2902.3.1"

Table P2902.3.1 lists values in inches "Away from wall" and "Close to Wall"

What's up with this??? Shouldn't Table P2902.3.1 be listing values that are distances from potable outlets to flood rim or receptors. What does distance "from or close to walls" have to do with anything as it relates to backflow? I assume the meaning of a receptor is synonomous with an overflow drain.

By the way-I notice you guys posting excepts from codes into threads. This must mean that you have them in electonic format. Where do you get these"? IRC, Florida Codes. And how much are they?

You must be confused! 3 post with the same topic in less than 15 minutes!

Originally Posted by Tom McDonnell

IRC P2902.3.1 "The minimum required air gap shall be twice the diameter of the effective opening of the outlet, but in no case less than the values specified in Table P2902.3.1"

No, P2902.3.1 says: (underlining is mine)

A112.1.2 and air gap fittings shall comply with ASME A112.1.3. The minimum air gap shall be measured vertically from the lowest end of a water supply outlet to the flood level rim of the fixture or receptor into which such potable water outlets discharge. The minimum required air gap shall be twice the diameter of the effective opening of the outlet, but in no case less than the values specified in Table P2902.3.1. An air gap is required at the discharge point of a relief valve or piping. Air gap devices shall be incorporated in dish washing and clothes washing appliances.

Table P2902.3.1 lists values in inches "Away from wall" and "Close to Wall"

What's up with this??? Shouldn't Table P2902.3.1 be listing values that are distances from potable outlets to flood rim or receptors.

It does.

At "away from a wall", read note "a" ... "a. Applicable where walls or obstructions are spaced from the nearest edge of the spout opening a distance greater than three times the diameter of the effective opening for a single wall, or a distance greater than four times the diameter of the effective opening for two intersecting walls."

If there are no obstructions "close" to the air gap, then the air gap may be less than if there are obstructions "close" to the air gap. Table P2902.3.1 gives the minimum air gap distance, twice the diameter minimum to whatever is listed. You will notice that 1/2" openings require 1" (2 times the diameter) or 1-1/2" (3 times the diameter), etc. down the table.

" Air gap devices shall be incorporated in dish washing and clothes washing appliances."
I don't understand. An air gap for a clothes washer? All I've seen have a rubber hose that hooks into the drain. Where is the air gap?

Originally Posted by Rick Cantrell

" Air gap devices shall be incorporated in dish washing and clothes washing appliances."

Rick,

Where is that from?

This is from the 2006 IRC. (underlining is mine)

- SECTION P2718
- - CLOTHES WASHING MACHINE

- - - P2718.1 Waste connection.

The discharge from a clothes washing machine shall be through an air break.

That drain hose hooked over the standpipe or laundry tub is an "air break" (but is not an "air gap").

By the way ... this has come up often, and its use has been incorrect.

- SECTION P2717
- - DISHWASHING MACHINES
- - - P2717.1 Protection of water supply.

The water supply for dishwashers shall be protected by an air gap or integral backflow preventer.

That is talking about what it says "The water supply for", not 'the drain from'.

continuing from the above ...

- P2717.2 Sink and dishwasher.A sink and dishwasher are permitted to discharge through a single 11/2-inch (38 mm) trap. The discharge pipe from the dishwasher shall be increased to a minimum of 3/4 inch (19 mm) in diameter and shall be connected with a wye fitting to the sink tailpiece. The dishwasher waste line shall rise and be securely fastened to the underside of the counter before connecting to the sink tailpiece.

continuing on even more ...

- P2717.3 Sink, dishwasher and food grinder. The combined discharge from a sink, dishwasher, and waste grinder is permitted to discharge through a single 1 1/2 inch (38 mm) trap. The discharge pipe from the dishwasher shall be increased to a minimum of 3/4 inch (19 mm) in diameter and shall connect with a wye fitting between the discharge of the food-waste grinder and the trap inlet or to the head of the food grinder. The dishwasher waste line shall rise and be securely fastened to the underside of the counter before connecting to the sink tail piece or the food grinder.

Jerry
I copied that from your post. The last sentence of the first paragraph.
Your next post (9:07) explains it well.
Thanks