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Thread: Dishwasher air gap vs. loop

  1. #1

    Default Dishwasher air gap vs. loop

    The discussion about the stinky dishwasher got me to wondering about the best way to reinstall my dishwasher. I pulled it out due to an incompetent electrical installation by the p/o of the house, but as long as it's out I figured I might as well check out the plumbing, too.

    The current setup has the drain line looped up behind the sink bowl and attached to the cabinet frame with a small strap. Standard practice around here is to use an air gap, but there's a problem: no hole in the sink to put one in. The sink is Americast, and drilling it voids the 25 year warranty, which I'd rather not do. The other option is to put the air gap in a hole in the counter, which is your basic cheap post-formed laminate.

    I'm not too worried about the present countertop, which is getting replaced as soon as I can afford it, but I worry about long term damage from having the air gap going through the counter rather than the sink and leaking water onto said countertop.

    So... what's your best guess? Better to have the air gap, even though it's installed in the countertop, or skip it and stick with the hose loop?
    Last edited by terry; 09-20-2004 at 01:46 PM.

  2. #2
    DIY Senior Member e-plumber's Avatar
    Join Date
    Sep 2004
    New York

    Question DW Air Gap or Not

    There really isn't a question about it, if local code requires one you need to have it, bottom line.

    Unless the kitchen sink is a "one hole design", you can purchase another style faucet that will allow an air gap to be installed in the sink if that's where you prefer it. Having it installed in the countertop is another option, obviously easier to do.

    Either way, unless there is a restriction in the DW drain hose or a clog somewhere, there isn't the chance of leakage or odors.

  3. #3
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default air gap

    Air gaps are always a potential source of leakage. Any restriction in the drain from the AG to the disposer, or tailpiece, can cause it to overflow. The looped drain is adequate until such time as a blockage downstream allows the sink to backup. Then the water can siphon into the dishwasher if it operates while the sink has standing water, or the standing water can flow into the DW if it fills the sink above the elevation of the drain hose's loop. In the event of that blockage an AG will overflow onto the sink or counter also.

  4. #4

    Default Dishwasher air gap vs. loop

    Thanks e-plumber and hcj for your cogent and helpful comments. You've given me exactly the information I need to make an intelligent desision.

    Air gaps are not required here by code but are commonly used; it's a matter of practice rather than code, so I can go either way.

    As far as the sink goes, it has four holes. Unfortunately, we have a brand new faucet which uses all four holes, although I could get rid of the sprayer. My wife likes the faucet and likes the sprayer, though, so in the interest of domestic harmony I'd rather not get rid of either.

    Since I'm not terribly fond of the existing cheap'n'nasty postformed countertop, I think I'll put in the air gap and see what happens. If it leaks and rots the counter, well, it needed replacing anyway.

    Thanks again for your help.
    Last edited by Chris; 09-19-2004 at 02:50 PM.

  5. #5
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    I was under the impression that you could drill an Americast, but regardless I would not do it. I also would not put the air gap on the countertop, because a leak here could "drift" to unwanted areas, like the floor!

    The "loop" method has been used for many years, with little or no problems. If you were to sell the house and need to "fix" it then you could replace your faucet with one which freed up a hole. Or you could remove the side sprayer and plug the faucet tube it was connected to.

  6. #6


    They do make faucets where the faucet head is also the sprayer, Chris. If you could get your wife to accept that, you'd have the hole for the air gap.


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