My ice maker has a gravity drain that it says to connect to the sink drain. All works well except if I run the faucet for a while eventually water will back up into the ice maker. I believe the issue is that the drain connects to a pump that pumps the water up into my sewage line, and my guess is when the pump kicks on it may back up the water in the pipe...but I am not sure if that's actually the issue or not. Picture of the setup attached, the grey line is what connects to the ice maker, the pipe closest to the wall goes up to a studor vent. Any ideas for changes I can make to stop this from happening? Is there a one way valve I can get for this or a different position for the grey line that would help?

Also side note, I plan to add a garbage disposal to the sink, is that a bad idea with the pump?


enter image description here

2 Answers 2


It appears to me that your problem is that the ice maker drain is BELOW the trap. So anytime there is water at that level, gravity will draw it into your ice maker drain.

I think you'd be better off locating the in the vertical section of sink drain ABOVE the trap.

  • Ah I was wondering about that, will definitely try it once I add the disposal this weekend.
    – Greg Myers
    Commented Sep 10, 2020 at 14:20
  • 1
    Yeah, at a bare minimum, have a nice, high loop in the ice maker drain hose. Put a hook in somewhere and support it as high above that drain as you possibly can. You want gravity working for you, not against you.
    – FreeMan
    Commented Sep 10, 2020 at 15:36

The placement of the connection of your ice machine drain is causing the wastewater to drain into your ice machine drain pipe.

  • With the faucet fully on, the section of the pipe highlighted in blue is filling with water.
  • When pipe is full and even with water flowing through that section, you can see that some water will be entering the ice machine drainpipe.

See picture below.

enter image description here

The other issue is that the ice drain should be connected before the P-trap. Attach the ice machine drain to the vertical section from the drain. Making the connection on the vertical section will likely force you to add a condensation pump to the ice machine drain. Many of the condensation pumps have a back-flow prevention valve on the outlet.

  • 1
    In the current setup there is no protection against sewer gases going into the ice machine drain. As you mention, it needs to connect before the ptrap. Commented Sep 10, 2020 at 16:13

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