Island loop for dishwasher

[LarsG35]

Hi everyone,

First off, thanks for the great site. Definitely a newbie here so I apologize in advance if I put this in the wrong place or have my formatting wrong.

My general questions are:
Would this be up to code [UPC] (or at least pretty close) and are there any functional differences between an island loop for a sink vs dishwasher?

More specific questions:
Are these cleanout locations correct?
Do I even need a high loop in this case? (No other waste water could get in)
If I need a high loop, does it need to be higher or lower than the level of the vent loop?
What is technically the "flood level" of a dishwasher? The high loop or just the bottom basin?
Should I put the cleanout above the Vent Tee when I connect back to the existing vent? Or is it fine as long as it's above the "flood level"?
Is this correct usage of Sanitary Tees and Wyes?


Some potentially useful information:
House is pre -1890s. Essentially assume that the walls are plaster over brick with random potential asbestos in the walls/ceiling. I really don't want to cut into it. Putting the dishwasher by the sink would require a complete kitchen remodel. I can't use an AAV - not to local code. As far as I can tell, this existing vent joins with the main waste stack vent in the attic. The existing vents/drains are all accessible in closets. It's probably reasonable to assume the existing drains/vents might not be up to current code, but we haven't had any smell/drainage issues. I already suspect that the horizontal travel to total length ratio of the vent will not be up to code, there's really nothing I can do about it because I'm not putting a new hole in the roof.

Attached is a diagram. I tried to do my best. Sorry if anything is ambiguous. Depth is compressed to a single dimension, but the utility sink is more or less directly under where I want to put the dishwasher. (for reference, this will probably require about 60 ft of new pipe)


Thanks for taking time to read my question! I'll try to respond quickly if needed.


Lars

 

[Breplum]

Your "foot vent" vent cleanout by the wall can be low. Height doesn't come in to play. You don't need a 'vent' tee at that wall either, you would be fine with a standard tee, upside down positioned.
The cleanout is not required on the returned loop vent. The cleanout on the drain is the only one required in that location.
I do not believe that foot vent has a distance limitation, so you should be fine.
UPC requires a DW airgap and does not allow direct connection of DW to sewer system.

 

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[LarsG35]

Thanks for the response breplum

Ok so I guess a standalone DW on an island isn't allowed in UPC? Or what would be the correct way to drain it then?
Something about an airgap sticking up in the middle of a 2' x 4' butcherblock island seems a little weird, but I suppose it makes for an interesting story.

I suppose I'm more interested to know if my set up is considered safe (in regards to sewer gas and backed up waste water) and will allow for normal dishwasher operation.

 

[Jeff H Young]

too many un needed cleanouts but that's not illegal
dishwasher airgap high loop don't fly on UPC you can run the high loop it just doesn't substitute the airgap

 

[John Gayewski]

You only need an air gap between the dishwasher hose and the standpipe. It doesnt have to be up through the counter top. The high loop isnt needed with an air gap.

 

[Breplum]

You can create a receptor with just the p-trap and 12 x 12 floor sink and have the DW drain hose stabilized over the floor sink. That is done all the time in commercial DW set ups and for icemaker drains. Not recommended for residential if it can be avoided.
You can also run the dw hose all the way over to the existing kitchen sink. They make dual inlet DW air gaps to allow two DW into one airgap.

 

[Jeff H Young]

yep no highloop needed only an airgap and true nothing says it needs to be like the standard DW airgaps on sinks

 

[LarsG35]

Ah, so I could just buy a dishwasher discharge tube extension and run it under the floor over to the kitchen sink? I had assumed that was against the rules for some reason! (rough picture attached)



The installation manual says a maximum of 16 feet of discharge tube, which I think is just enough to make it work.

I'll run it up to an air gap (already have a spare hole in sink) and then to a tailpiece with dishwasher connection.

That would be much cheaper and simpler.

Thank you for the suggestion!

 

[wwhitney]

Minnesota appears to have amended UPC 807.3 to allow a high loop instead of an air gap:

807.3 Domestic Dishwashing Machine

No domestic dishwashing machine shall be directly connected to a drainage system or food waste disposer without the use of an approved dishwasher air gap fitting on the discharge side of the dishwashing machine or run the discharge line as high as possible under the countertop, securely fastened. Listed air gaps shall be installed with the flood level (FL) marking at or above the flood level of the sink or drainboard, whichever is higher.

Chapter 8 Indirect Wastes: Indirect Wastes, 2020 Minnesota Plumbing Code | UpCodes

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Cheers, Wayne

 

[Jeff H Young]

That will make things a little easier.