I will soon embark on installing the plumbing for a dishwasher. The distance of the dishwasher is too far away from the sink to be connected. I am wondering whether the following will work.

Install a separate ptrap and vent pipe to the existing venting system. On the inside of the ptrap, install a dishwasher tailpiece pipe. The new ptrap and the existing sink ptrap are vented from outside the house. Also, put a clean out on the new trap.

Yes, it will work. Just be sure there's a high loop in the dishwasher drain, and an air gap if possible.

Thanks for your reply.

Why is an air gap recommended given that the ptrap will be vented? Can it reside inside the cabinet or must it be above the loop?



Edited 1 times.

i would install like a washing machine standpipe as high as possible inside the cabinet

don't use a d/w tee

use a 'hook' piece of copper tube inserted into the 'standpipe'

you would not have an actual air gap, but you WOULD have an air break/vacuum break

imo: not best, but, good practice


'can anyone explain better?'

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

I don't like the idea of a standpipe either, especially one that is open with an air break inside a cabinet.

What I'm thinking is to have a properly (outside) vented ptrap that's connects the dishwasher via a tailpiece pipe. Nothing's opened. I could even put this just below the ceiling downstairs.

The idea behind the air gap is to prevent germs and bacteria from getting back into the dishwasher from the drainage system. Most codes require them.