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Im finalizing my plumbing for my workshop, I've got a 3" main drain and planned 3" wet vent for the plumbing. The sketch is my current plan. The lowest two "entrances" on the stack had to be reducing combo sweeps in order to clear the purlins and stay low to the slab; though I suspect santitary-tees would be called out if it was a continuous 2" pipe meeting a 2" pipe.

So my question is: have I selected the two red long sweep wyes correctly? Side to side this whole contraption is about 12', so it is very tight. Blue represents 3" ABS, Black 2" and green is 1.5" primarily for vents. The Dual-sanitary Tee in the middle can have a vent line tied back to the main stack if that is required, but it is not shown and otherwise it will be caped. It sits about 1 foot from the stack. (Image updated to draw P-Traps correctly and NOT S Traps) enter image description here

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  • Why are all your P traps drawn as S traps? Are you planning on S traps? Mar 8 '21 at 23:10
  • Purlins being structural roof members? Mar 8 '21 at 23:16
  • Good point, they are supposed to be p traps but I cant draw. And the purlins are the 19.2 on center metal wall structure. The image is a side view looking at the outer wall.
    – mark f
    Mar 9 '21 at 2:19
  • You might want a double Y and 1/8 bend instead of the double sanitary tee - pmmag.com/articles/… Mar 9 '21 at 17:58
  • I am morbidly curious about what a "Combo Urinal Sink" is. Something tells me I really don't want to know.
    – FreeMan
    Nov 30 '21 at 15:42
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Updated Answer:

Issues with the posted arraignment (see last photo for number references):

  1. The fall on the urinal drain exceeds the vent.
  2. The vent serving the shower and urinal transitions to horizontal at a height that might be below the flood level rim of the urnial.
  3. This connection is not required as the sink above would provide a wet vent for the lower sink. In addition this connects the vent below the flood level rim of the lower sink.

There are many ways to pipe drainage systems. One way would have been:

enter image description here

In this example, the urinal, shower, and lower sink are all vented through a single 2" wet vent (the wet vent portion is shown in blue). The upper sink needs to be kept separate as the load would exceed the allowable load on a 2" wet vent. The vent and the drain from the upper sink would need to cross, but it looks like there is room to do so provided you offset the vent nominally vertical with two 45º elbows.

There are issues with the original sketch such as how are the toilets being vented? Below is how I would have piped it.

enter image description here

Original Clarification Request:

The original sketch and the picture of the installation have potential code issues. Please confirm that the below sketch correctly illustrates the final arrangement:

enter image description here

Can you also confirm what was done with the upper fixtures shown on the original sketch (kitchen sink, toilet, lav sink, and shower) as well as the most downstream toilet?

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  • your labels are correct. the 'What is this Serving" is the drain line for an upstairs lavatory sink with its vent upstairs. The "Is this correct" is a dry vent for the shower tying into the vent also used for the work sink. As to the upstairs, I think only the sink was changed (which now empties into the middle 2" line down below. Another difference up top was the kitchen and shower wye T go to a 3" pipe feeding the main wye 3" to the stack. (the kit sink is capped and not plumbed in yet). there is also a bunch of hot &cold PEX feeds, a manifold, and OD-heater in the same wall...
    – mark f
    Nov 29 '21 at 22:20
  • ppd Thank you for your review. I dont know why i dint consider wet vent in my original layout.... As to your comments: 1-the urinal 2" drain is sort of wet vented past the emergency shower about 6'. 2- the tiny urinal lip is just below the horiz vent line at its lowest. 3- good catch! the sink vent is below the flood overflow of the sink ( ill look at moving it). The two toilets are both about 15" from the main 3" stack, so is that a sufficient "wet vent"?)
    – mark f
    Nov 30 '21 at 22:53
  • The fall on the urinal's fixture drain exceeds that the diameter of the fixture drain's pipe and therefore cannot be considered as wet vented though the shower's vent, it would need its own vent. If you replace the 90 with a tee and continue a vent off the top of the tee, the shower would be wet vented through the urinal's vent and you could eliminate the extra vent piping after the shower.
    – pdd
    Dec 2 '21 at 0:28
  • Regarding the toilets, the upper toilet would be considered as vented through the stack's vent however the lower toilet would not meet the requirements of wet vented toilets where I live. Here wet vented toilets must be the last fixture drained in the wet vent, however you have one at the top. Additional, you have multiple branches connecting into the vertical portion which would not be allowed if it was a wet vent.
    – pdd
    Dec 2 '21 at 0:28
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Minor Mods to the original plan, but kept the final stack and all the plumbing in one wall. We did end up using rubber couplers on the 3" stack to give some compliance in orienting the pipes since they took up nearly ALL the free space in the wall. [![enter image description here][1]][1]

[1]: https://i.stack.imgur.com/ePg2K.jpg![enter image description here] And here is the dreaded "urinal sink" combo (https://i.stack.imgur.com/Eq7Ue.jpg)enter image description here

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  • Not sure where you are located but there may be multiple code issues regarding this arrangement.
    – pdd
    Nov 29 '21 at 21:03
  • I am in Pima County, Arizona USA, please add detail of your code concerns... thanks in advance. Lower pipe has a urinal and a shower (and vent to right) middle has sink and vent tied all the way to the right. Upper is the vent reverse sloping... vents are not like the original sketch...
    – mark f
    Nov 29 '21 at 21:17

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