Running drain (and vent) lines for stacked, identical bathrooms

[Timothyr64]

I am in Penna. And I want to put in two identical bathrooms stacked on top of each other. The attached sketch is pretty rough, but basically there is a 4" stack that runs from the basement, up thru both floors. At both the first and second floors I want to come off the 4" vertical stack with a 4x4x4 T, off that (horizontally) a 4x4x2 T that would pick up the shower, than put in a long sweep 90 to head over to pick up the toilet. Just prior to the toilet, put a 4x4x2 Y and extend the 2" up thru the wall and pick up the second floor toilet vent and take that 2" pipe up thru the roof to vent both toilets. IS ALL OF THIS OK?
My next question is, since the sink (s) and shower (s) are both within 36" of the 4" vertical stack, can that be used to vent those fixtures? I guess this would be a wet vent? On one hand I'm thinking that is not allowed? But on the other, would it still work because it is a 4" pipe? Although I was thinking of reducing it to 3" before it goes thru the roof.

 

[NHmaster3015]

Does the 4" stack serve other fixtures or is it just a vent? If its a vent, you can't put anything into it other than other vents.

 

[Sponsor]

 

[hj]

About the only "legal" things in your drawing are the lav and toilet, but NOT the shower, on the upper level. Everything else, including reducing to 2" through the roof, has to be "rethought" and redone.

 

[Timothyr64]

It previously was used as a stack. Only fixtures going into it are ones mentioned. I was going to use it as both a stack and a vent. Which apparently is not allowed?

 

[NHmaster3015]

Nope, it is not allowed.

 

[Timothyr64]

So I can only use it as a stack. Must run seperate 1 1/2" vents up to above fixtures on second floor and than tie them into stack? And / or run them out seperate? Can I reduce stack to 3" before going thru the roof?
Am I ok with the shower drain going into the same 4" horiz pipe as the toilet? Or should they go directly into stack seperately?

 

[NHmaster3015]

I don't know. Without being there to see exactly what is going on its pretty hard to make a recommendation.

 

[Terry]

Seperate vent stacks and seperate waste stacks.
The moment you run waste down a floor, it needs to be only waste, as it will either push water out of the traps and bowls, or suck the water out.

Vents can tie back together at 6" above flood level, or in most homes that means 42" above a floor.
The vents from the downstairs would tie back in at 42" above the on the second floor.

If the 4" vent from the basement is used to vent the basement bath, then no waste can go into that. You will need to open the floor and wye in downstream of the basement bathroom.

 

[hj]

IF you connect the tub/shower to the toilet line, it MUST have its own vent ahead of that connection. Your city's code will determine WHAT you can do with the vent out the roof. Some allow a reduction, some require multiple vents if you reduce it, and others do not allow a reduction regardless of how many vents you have.