I've had this house a little less than a year. We've had issues with nasty water turning up in our dishwasher. We assumed there was just something wrong with the dishwasher/filter, etc...

Upon inspection of the drain setup, the dishwasher is plumbed in directly to the top of the garbage disposal. We discovered water from the sink was making it's way right into the dishwasher.

It seems, that there is supposed to be an "air gap" fitting installed, that I assume is what would prevent this from happening. There appears to be no such animal in this install, and the port from the GD is plumbed directly to the dish washer.

Is an air gap setup all I need to resolve this? I was debating on skipping the garbage disposal and plumbing directly to the drain pipes, as it would be a lower point in the system, and less likely to cause drain back to the dishwasher.

  • 1
    As a quick stopgap you can try attaching the dishwasher hose to the underside of the counter, but an air gap is a better method. I have an old install from before airgaps were required and/or common, and the loop to the countertop is effective so long as the sink is not absurdly full. One small plus to running into the disposal is that if you operate the disposal as the dishwasher is draining you have more water running through it as it operates than what you get out of the faucet alone.
    – Ecnerwal
    Commented Jun 20, 2017 at 16:08
  • @Ecnerwal I remember when my dishwashers were installed (~ 17 years ago, Whirlpool) that they included instructions using the hose looping up as the actual air gap, which was a nice improvement from the old air gaps I remember sticking out of the edge of the sink top. I would think that would work for almost any dishwasher, as long as there is space under the sink to run the hose high enough. Commented Jun 21, 2017 at 1:27

1 Answer 1


having just redone the dishwasher, sink, disposal and faucet/drains in my kitchen I can hopefully help you here. You shouldn't need an airgap for one. I actually removed mine when I redid them because I found it to be ugly and both the dishwasher and disposal manuals say one was not necessary. What you can do is loop the dishwasher drain hose so it reaches above the connection to the disposal, this should keep stuff from running backwards into the dishwasher. I am however concerned that this is happening in the first place and might suggest checking your disposal to see if it is clogged or having other drainage issues as the water level in the disposal shouldn't ever get high enough for water to backwash down the to the dishwasher.

Also running the dishwasher into the disposal is beneficial so any large food waste goes through the disposal instead of directly down your drain so I wouldn't change that part out.

I would also double check your manual for your dishwasher to see if it has special instructions for the connection without the airgap.

  • What happens is the hose goes directly down and is too short to loop. In times where the garbage disposal hasn't been run, and it drainage is slow, it seeps down into the dish washer. If you are running the GD constantly to keep it clear it isn't a problem, but I can't count on everyone to do that. I'll start with the loop idea first and purchase a longer hose, as I think that'll likely solve it.
    – slambeth
    Commented Jun 27, 2017 at 16:46
  • Honestly it sounds like you might want to put less food down your garbage disposal/dishwasher if its enough to clog the drain a bit. Disposals are both a blessing and a curse in this sense because while it helps keeping large stuff from clogging up drains it also trains one to put stuff into the drain that normally we shouldn't.
    – OCPik4chu
    Commented Jun 28, 2017 at 14:28

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