Wet Venting bathroom group in new construction (Under Slab)

[Eben]

Hi All,

I am building a home which includes a bathroom group in the basement with under slab plumbing;

IRC 2009 (Upstate NY).

Having read the code backwards and forward I think I have a layout that should work just fine, have been reading this forums but decided it would be just to just ask.

I am attaching a photo, but briefly:
*4" under slab drain @ 1/8 slope
*Toilet connects via wye 4" run to toilet, then 3" to 4" flange adapter plate (About 8' away from vent stack)
*4x4x2 wye for shower -- less than 8 ft of total pipe from shower to vent
*lav drains into vent (making it a vertical wet vent?)
* lines marked "-V" are vertical (for the avoidance of doubt)

I think this should be good?

My other question, which is somewhat theoretical: IF I have a 2" trap, then I tie into a 4" pipe, can I have a longer wet vent than if I only used a 2" pipe. In my drawing, this would mean changing the shower wye from a 4x4x2 to a 4x4x4 and then dropping to 2" pipe right at the shower. I assume the answer is "no" and wet vent distance are set based on the trap size, but I'm curious!

Thanks for any feedback-

Eben

 

[Eben]

Hey Everyone,

i'm adding an updated drawing which hopefully is a little clearer-- the upper left corner is the wet vent stack (the other stack receives WC discharge).