Currently my kitchen Plumbing is torn apart. I had new countertops installed and the plumber came today and said the top gas cap ((?) protecter from fumes I'm assuming) no longer fit and CUT it off. He left to get new parts, never to return... So, I'm installing my faucet and replacing the PVC starting just under the Y that attaches to a P-Trap. I've been told by a licensed plumber that the P-Trap is "old school" and the dishwasher drain line can go directly into the disposal. I see where it could be attached, is this correct? I'm a "Shemale" Landlord, I've got a little experience with plumbing but far from a professional!! Appreciate any advise!

  • My dishwasher drains directly into the disposal. You probably will need to install an air gap in the dishwasher drain line.
    – BillDOe
    Nov 7, 2015 at 23:34
  • If your dishwasher drains into the disposal then you typically do not need to install an air gap. The disposal acts as the air gap instead.
    – Michael Karas
    Nov 8, 2015 at 0:22
  • 2
    Note that if this is the first time a dishwasher drain has been installed onto the disposal it will be necessary to remove a knock-out plug that is just inside the hose attachment pipe. On most disposers that I have seen it can be removed using a hammer and punch. This will make the plug break loose and pop inside the disposal. Make sure to take the loose plug out before trying to use the disposer again.
    – Michael Karas
    Nov 8, 2015 at 0:27

2 Answers 2


Yes. The disposal unit should have a barbed inlet that is intended to receive the dishwasher's drain line.

As others have mentioned, be sure to check that the knock-out plug has been removed from inside the barbed inlet. You can remove it by using a screw driver and a hammer.

Also be sure that you run the dishwasher drain hose up to the underside of the counter, securing it there with a clip and back down to the disposal connection. The hose is secured with a pinch or gear clamp.

Both the dishwasher and disposal unit's instruction manuals should show how to do this.

  • 1
    When pdd says above to "run the dishwasher drain hose up the underside of the counter" he's describing what is called a "high loop" - make sure you have that. Note that some dishwashers have this built in as part of their hose routing (they loop it up the side or back to a clip at the top of the dishwasher). Notwithstanding this fact, I think some state building codes will still require you to do your own high loop.
    – RobotAndy
    Feb 19, 2016 at 13:47
  • @RobotAndy Yes, that is what is being referred to.
    – pdd
    Feb 19, 2016 at 18:00

If you don't have the loop, you will most likely get a foul smell. Mine still smells with the high hose. I would think a goose need would help as it uses water as a barrier from the sewer(disposal) to the appliance.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.