Anti-Siphon Valves (Air Gaps)


The lack of a surface mounted air gap (anti-siphone valve) usually results in some controversy. I will try to explain the need for this device as easy as possible. A surface mounted valve (air gap) is usually chrome in color, (other colors are available), that is mounted on the top of the counter near the kitchen sink. The lack of this device can create a potential health hazard due to contaminates that originate in drain pipes, drain trap, or the garbage disposal from siphoning back into the dishwasher, and because the water supply to this appliance enters level to, or below the drain line, it is necessary to prevent cross connection, or back siphoning which could allow drain water to mix with supply water. One can imagine the health risks in any one of these events.

Most of the newer high end appliances have a built in anti-siphon device or integral backflow device that is connected to the drain hose from the dishwasher, and is clearly visible inside the cabinet under the kitchen sink, and an additional air gap on top of the sink may not be necessary, Miele being one of those brands. Manufacturers installation instructions should always be followed. If the installtion instructions indicate that this device is not needed because of the factory built in valve, then that is what dictates whether a surface mounted device should be present. Local building departments do have differing views of these built in devices as to whether they are accepted or not, and I recommend referring to installation instructions, and inquiry with the governing building department in regards to their specific requirements.

Unless otherwise stated in the installation instructions, the "UPC 807.4 states that "No domestic dishwashing machine shall be directly connected to a drainage system or food waste disposer without the use of an approved dishwasher airgap fitting on the discharge side of the dishwashing machine. Listed airgaps shall be installed with the flood level (FL) marking at or above the flood level of the sink or drainboard, whichever is higher".

 Anti-Siphon Valve

6 Responses to “Anti-Siphon Valves (Air Gaps)”

  1. Greg Dyer says:

    We have an anti-siphon valve as you describe and we have been told it is not functioning properly. When the DW is running, sounds like when draining, wather flows out of the anti-siphon valve into the sink. I replaced the part with one form Lowes, and it still does it. Would you please tell me what is going wrong and how to fix it? Thanks

  2. Hi there, I just come across your blog browsing on Google as I am researching some info on dishwashers. Looks like a cool blog so I bookmarked you and I will come back tomorrow to have a more detailed read when i have more time. Great site!.

  3. admin says:

    Most likely the hose that attaches to the garbage disposal is clogged, and will need to be cleaned. Simply disconnect the hose at the disposal, clean it out and re-attach.

  4. Yeowsers!! says:

    Yep, mine was a clogged drain hose to the disposal.  Pretty nasty.  Make sure you've got a bucket underneath.

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