Dishwasher w/o vacuum breaker

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by pacermb, Sep 28, 2007.

  1. pacermb

    pacermb New Member

    Sep 28, 2007
    Dishwasher w/o vacuum breaker/air gap

    I want to plumb a dishwasher through my garbage disposal without using a vacuum breaker/air gap. How is this done?
    Last edited: Sep 28, 2007
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Illegally, in many places!

    I think the term is air gap. But, to help, but not prevent, backups in the sink getting into the DW, run the hose as high as possible and clipped to the bottom of the counter, then run it down to either the garbage disposer's inlet, if using one, or a dishwasher tailpiece you install in the drain above the trap.

    Note, if you've never hooked a DW up to the GD, make sure to knock out the plug on the inlet AND remove it from the inside of the GD. Generally, a stout screw driver and a hammer will dislodge that plug.


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  4. msgale

    msgale Member

    Sep 28, 2006
    are you sure...

    you haven't been at a home where a clogged/filled disposer sink backflowed through the dishwasher, flooding the kitchen with sink waste.

    i saw that once, and that is enough for me to always put an air gap.
  5. Verdeboy

    Verdeboy In the Trades

    Jun 12, 2006
    In my experience, flooding ocurrs much more with an air-gap than without one.

    When that inlet into the G/D gets blocked with food, the entire contents of the dishwasher will drain through the air-gap and onto the your kitchen counter and then onto the floor.

    I've seen that scenario dozens of times. I've yet to see the scenario you've just described.
  6. Mike Swearingen

    Mike Swearingen New Member

    Jan 12, 2005
    Independent Real Estate Broker
    On Albemarle Sound In Northeastern NC
    I have had a dishwasher since I built this house 30+ years ago. I don't have and have never had an air gap or a disposal (on septic system).
    I have NEVER had any problems. Ever. I just loop the dw drain discharge hose over the top of the dw and away it goes. No back up.
    I never have "backup" because I use an enzyme-based drain cleaner (like DrainCare) that keeps everything cleaned out and all flowing out of here as it should.
  7. Dunbar Plumbing

    Dunbar Plumbing Master Plumber

    Apr 18, 2005
    Service Plumber, Outdoor Temperature Relief Owner
    Northern Kentucky/Greater Cincinnati Area
    There's a reason for its use

    There's a reason why in all 50 states it is mandatory on restaurants, church kitchens, home catering businesses that have a commercial kitchen.

    It's designed to protect in the worse case scenario, that is why a good deal of the states in the united states require them.

    Case histories of cross-connections whereby wastewater has travelled back into the dishwasher.

    That is a common forum topic found on any plumbing/DIY'r forum. It happens and the lack of an Air Gap is why it happens.

    High looping is the same as throwing a hose over the edge of your swimming pool and draining it; Once the momentum starts, it has the capability to reverse the flow other than its intended direction.

    When a Air Gap leaks, the device isn't defective, it's the pipes leading from the Air Gap that causes the issue.

    Here soon I'm going to find out the regulations for these devices in every state and post them. Kentucky has enforcement of these and have been for years.


    Last edited by a moderator: Feb 3, 2019
  8. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    air gap

    If the hose is looped up to the bottom of the countertop, then the only way for the water to enter the DW is either because the drain is plugged and the sink is full of water, in which case they should have stopped running water a long time ago. Or, the drain is plugged and there is water in the sink and when the DW finishes pumping the water out, it siphons it back into the DW. Again this should be obvious and a plumber should be called. In either of these scernarios, if the DW has an air gap the drain from it will be restricted by the water in the sink and the DW will drain onto the countertop, again alerting the occupants to the need for a plumber.

    Last edited by a moderator: Dec 23, 2007
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