NSPC stack venting question

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Burlington, NJ
I'm definitely a novice when it comes to plumbing, but I took out a kitchen on the 2nd floor and was hoping to replace it with an additional bathroom. I'd really like to try to tackle this project myself. From what I've read, I'm thinking I should be able to stack vent the bathroom group, but I have a couple of questions I was hoping someone could answer. Here's the passage from the 2006NPSC on stack venting:


12.11.1 Fixture Groups
a. A single bathroom group and a kitchen sink (with or without a disposer and/or dishwasher) located back-to-back, or two bathroom groups back-to-back may be installed without individual fixture vents in a one-story building or on the highest branch of a stack provided that the following conditions are met:
1. Each fixture drain connects independently to the stack.
2. The tub and/or shower and water closet enter the stack at the same level.
3. The requirements of Table 12.8.1 are met.
4. A side inlet connection into a 4" closet bend shall be considered to be an independent connection to the stack.

My stack runs vertically along the OUTSIDE of the building and terminates below the roof with an elbow. I know that this is less than ideal in freezing weather, and at the very least I'll have to take the vent above the roofline, but the plumbing inspector won't tell me that I need to move it inside the house, will he? The NPSC says that no NEW building can have a stack running up the exterior, but what about one that is already there?

I'm also curious about the side inlet closet bend provision. Does that mean I can run a 4" pipe 12 ft from the stack to the closet bend (the maximum length from trap to vent for 4" pipe) and then connect 5 ft of 1 1/2" pipe from the tub to the side inlet and still be vented and drained properly according to the code? I don't need to run anything that long, but I just want to make sure I understand that section. I'd rather connect the tub to closet bend so I don't have cut another hole in the exterior wall. Does anyone have a source for a 4" closet bend with a side inlet? I can't seem to find one anywhere.

Maybe I'm in over my head and I should just call a professional. :confused: Thanks for your help.
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