Zig-Zag undersink plumbing?

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Ivan Blackford

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Hi All,

I apologize if this is a simple question and has been answered before. I'm trying to rectify a very poor drain plumbing install under a double kitchen sink. The pipe comes up through the bottom of the cabinet and is not vented. I don't have access in the ceiling below to install the trap below the floor, so I would like to do the following:
1666798751986.png


Assuming i respect all my slopes, vent arm and trap arm distances, is this permitted in Ontario? The only thing I can see that is different from a standard installation is that the drain zig-zags under the sink, and I haven't seen this practice used before.

Thanks in advance,
Ivan
 

Terry

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I see both having a drain going through the bottom of the cabinet, and both having an AAV above the santee for the p-trap arm. Does left or right side of the cabinet matter? I mean, what about left handed people?
 

Jeff H Young

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More zig zag doesn't make it more better. it'll work just a matter if, quality or workmanship is an issue perhaps space under cabinet as well . but these parts are super cheap but if you are upcycling or reusing saving the planet type thing then run what ya brung!
 

Ivan Blackford

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My concern was that water from the leftmost sink has to flow right towards the right sink, bend 180 degrees, and then head towards the trap. I'm not sure if this is allowed or not, but it sounds like i may be overthinking it. :)

Ivan
 

Tuttles Revenge

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sounds like i may be overthinking it.
Yes. The least distance and turns the better, but gravity is going to work for that additional 30" the waste travels from one Zig to the Zag where it goes vertical. Likely you could pipe the Right hand sink to the left and drop directly to a trap there to make it 30" more efficient, but you're good to go either way.

And to slightly modify your drawing, you would want to extend your trap to directly under that right hand sink so that the Tee drops straight down into the trap..
 

wwhitney

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Got it, thanks! For my final answer, I shall do this:
One correction: the green horizontal segment you've drawn between the san-tee and the AAV shouldn't actually be horizontal. I.e. if you need an offset between the san-tee and the AAV, use two 45s, not two 90s.

Cheers, Wayne
 

Tuttles Revenge

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AAV's are only required to be 4" above the p-trap which should help in possibly not needing any offset. But the best offset would be 45° bends as Wayne points out under the flood level of the fixture.

2015 National Canadian Code
2.5.6.2. Vent Pipe Connections 1) Vent pipes shall be installed in a nominally vertical position where it is practical to do so.
 
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Ivan Blackford

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AAV's are only required to be 4" above the p-trap which should help in possibly not needing any offset. But the best offset would be 45° bends as Wayne points out under the flood level of the fixture.

2015 National Canadian Code
2.5.6.2. Vent Pipe Connections 1) Vent pipes shall be installed in a nominally vertical position where it is practical to do so.
Thanks for the advice, I get the reasoning for not wanting it horizontal at all, given that if the drain backs up, water will go into the vent pipe, and it wouldn't have a good way to exit if the pipe is horizontal. I plan to tuck the AAV as high up as I can beside the sink, such that it's as close as I can get to the flood line of the sink.
 

Ivan Blackford

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One last question, is there a restriction on mechanical take-apart joints in a DWV system in Ontario? I would like to put one of these just above the cleanout, so that I can remove the entire undersink assembly in the future for cleaning or AAV replacement:
1666880685127.png
 

Tuttles Revenge

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I've never seen that fitting before. I use a shielded No Hub coupling to create a Union when I'm building kitchen sink drains out of all ABS/PVC drainage fittings. The above style of fittings suffer if they're ever slightly out of alignment.
 

Clarice8419

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Both have a drain that exits through the base of the cabinet and an AAV above the Santee for the p-trap arm. I had the same problem with two sinks connected in series and one p-trap vented through an AAV, and I engaged plumbing services to fix it.
 
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