Attached a video demonstrating the symptom, and pictures of the setup. Video starts just before the Drain Cycle ends. Once it ends, air slowly enters from the disposal-end, pushing all the water from the top of the high loop back down into the dishwasher. It rests near the bottom, where the water level ends up inside the dishwasher. Shouldn't this not happen?

Video example

Angle 1 Angle 2

  • In the video, you can also see at the end of the water travelling back, some air bubbles through the bottom loop
    – Headache
    Commented Jul 27, 2019 at 19:49
  • The photos don't show how the plastic drain hose is connected to the drains. Commented Jul 28, 2019 at 3:53

2 Answers 2


so some of the waste water from the dishwasher returns to the dishwasher when it finished pumping that's completely normal. There's no real way to prevent that.

So long as you don't get water from the sink or from the drain flowing into the dishwasher everything is fine.

  • Confirmed with a few more sources, this does get returned to the dishwasher. Not using the dishwasher for an extended time can cause some funky smells but it's not from sinkwater backing up at least. Thanks!!!
    – Headache
    Commented Jul 28, 2019 at 21:38

This is exactly what an air gap is supposed to prevent. This is something that sits on the edge of the sink, and lies between the dishwasher and disposal, but I don't see one in your setup. This ensures that any backflow pressure won't go all the way back to the dishwasher. You can buy one at any home improvement store, but installing it might be annoying.

  • 1
    Needed info for a more clear/complete answer: The drain hose is connected to the air gap, the air gap is installed through a hole in the sink or counter top near the edge of the sink. Your sink may have a hole already in place you can use or you may have use a hole saw to create one. The hose connects to it and then another hose from it down to the disposal/drain.
    – Alaska Man
    Commented Jul 27, 2019 at 20:54
  • See this: balkandraincleaning.com/air-gap-plumbing-pipe-systems
    – jwh20
    Commented Jul 27, 2019 at 21:26
  • I'd like a bit more information on this, because there seems to be some confusion about what an air gap actually accomplishes. The high loop is allegedly a "safe" alternative to an air gap when done correctly, something that prevents backflow when the connected drainage system backs up. In other words, it prevents dirty sink water or, if for some reason failure causes sewage to build up (ew), it won't go down into the dishwasher. I don't have an issue with sink water going down the hose. I have an issue with the dishwasher water returning to the dishwasher.
    – Headache
    Commented Jul 27, 2019 at 22:17
  • Since the dishwasher "waste" hose I guess is connected to the plumbing of the sink, if the hose had no loop, some of the dirty sink water would travel down the hose. If the hose had too low of a loop and the sink filled past the top-most part of the loop, dirty sink water would travel down the hose. Neither of those scenarios apply here. From what I understand, the air gap just makes it impossible for dirty sinkwater or sewage to return to the dishwasher, because then it would overflow out of the sink before being able to go down the dishwasher hose.
    – Headache
    Commented Jul 27, 2019 at 22:26
  • @Headache you do not have a high loop in your hose. Your hose goes up and then down to the disposal. You need to take your hose up then around in a loop ( circle ) and then down to the disposal. The air gap is a better way to go.
    – Alaska Man
    Commented Jul 27, 2019 at 22:39

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