I am having a new, deeper stainless steel sink installed with the new countertops. The garbage disposal will now sit lower below the sink than the old one did. The waste from the disposal exits through a horizontal discharge tube, down the p-trap, and up/out through the main wall drain.
The discharge tube coming out of the disposal will sit slightly higher than the main drain pipe going out of the back of the cabinet. If all goes as planned, the bottom of the disposal discharge tube will sit right above the top of the wall drain pipe. However, it may sit just a little lower. I read somewhere that the center of the disposal pipe must sit at least 1/4" above the center of the main drain pipe so that water doesn't collect in the bottom of the disposal. I'm wondering if this is correct or if there is a different minimum distance that the wall drain pipe must sit above the disposal discharge tube in order to drain effectively? I really don't want to have to hire a plumber to lower the main drain pipe if my plan described above will work.
Thank you!

Has to sit higher or water will just sit in the disposal. That is a recurring problem with deep sinks.

Thank you for your reply. I understand that it must be higher, but is there a "set amount" higher? Does the whole disposal pipe need to sit above the wall drain pipe, or is it o.k. if just part of it sits above?
Thank you!

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Originally Posted by mgreen4

Thank you for your reply. I understand that it must be higher, but is there a "set amount" higher? Does the whole disposal pipe need to sit above the wall drain pipe, or is it o.k. if just part of it sits above?
Thank you!

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The bottom of the outlet needs to be no lower then the top of the wall pipe. Even then, the p trap and all piping will be filled with water.