Hello, So I have a dispute I have to settle. I am an appliance technician. I have an issue in a building where they have two dishwashers hooked up to a Y connection to the dishwasher. No high loop and no air gap. The plumbers and the superintendent insist the problem is with the dishwasher. They say this because in the other apartments this is not happening. The issue arises in this apartment because the customer uses only one dishwasher, after a few days the other dishwasher fills with enough water to almost over flow. I work in NYC. I know that I am not a plumber so my knowledge is too limited to say with certainty that this is wrong. so here are my questions.

What would be the correct way to connect these drain lines to a single sink with a garbage disposal?
Is that Y connector acceptable?
Is the plumber wrong in assuming the dishwasher's non return valve should be able to hold back drain water from filling the dishwasher no matter how this is plumbed?

[imgur.com]

high loop the drain hoses.

So having it connected with that Y connector in the image is ok otherwise?

from the pic it look like there is no trap?

There is a trap after the connector coming out of the garbage disposal its at an angle I didn't get in the picture.

Have you removed the drain hose from the pump of the dishwasher that's being filled ? I agree with them that the internal check valve should keep that from happening. That being said, if you high loop the hoses and check for any obstructions just downstream of that copper tee it should work ok.

If you hae two sinks, hook one to the disposer and the other to a dishwasher branch tailpiece. The discharge pressure will always force water into the other machine.



Edited 1 times.

At a minimum, high loop and swap hose locations on that (not really a wye) wye. Better to high loop and install a DW drain wye.

Yeah unfortunately they only have one sink.

would you attach that to the garbage disposal? or does it need to be connected elsewhere?

Disposal.

Thanks, btw isnt that WYE for drawer dishwashers? Also if there was a restriction at the garbage disposal because of debris wouldn't that put back pressure on the dishwasher that wasn't draining and cause water to migrate into the other dishwasher?

use the DW drain 'Y'

AND

'hi loop' the discharge lines

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