We have a new dishwasher that was installed by the retailer. A month later we installed a disposal our selves. Now the dishwasher is not draining. Any suggestions?

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    Did you remove the knock out plug in the drain line? (sorry, not sure exactly what the technical term is... it's a plug that's supposed to be there if you don't have a d/w attached). Youtube etc will have instructions on how to remove it. Apr 13, 2015 at 23:59
  • @AloysiusDefenestrate - You should make this an answer as it is a very very likely cause of the OP's issue.
    – Michael Karas
    Apr 14, 2015 at 11:29
  • @AloysiusDefenestrate - It's an answer, convert it and collect upvotes. Drift pin and a hammer will remove the knockout. It's cast in with a thin groove to allow it to break out, use a mirror to make sure you get all of it. Not everyone has a dish washer, or may have a double sink with vacuum breaker and y fitting on the other basin. Apr 14, 2015 at 15:50
  • @Michael Karas, Fiasco Labs -- you guys are too kind. I'll add an answer. Apr 15, 2015 at 1:20

1 Answer 1


Seems likely that the knockout plug in the drain line on the disposal unit needs to be removed. (It's there for people that aren't connecting a dishwasher.) User Fiasco Labs likes a drift pin and a hammer; I've used a socket on an extension and a hammer. Either way, make sure you don't leave any bits behind.

If that's not the root cause, comment back and we'll do our best to sort you out.

  • 1
    I would like to add that since the OP already has the disposer installed they may try to remove the knockout with the unit in place. This will cause the plug to end up inside the disposer. The OP need to take extra special care to unplug the disposer (or shut off the circuit breaker) and then reach into the disposer and remove the plug and what ever other pieces may come loose when the pounding is finished.
    – Michael Karas
    Apr 15, 2015 at 5:18

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