Venting for Sink and Shower into Macerator

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I'm adding a bathroom in a recently-enclosed garage. Instead of busting up the concrete and trenching to the septic tank, I'm feeding this into a macerating toilet, which I'll then tie into a nearby line that goes to the septic.

My question is about venting. I've roughed in a configuration, but I want to make sure the venting will work (specifically, if the sink vent can also serve as the shower vent in this case).

In the attached picture, could A serve as the vent for the sink (B) and shower (C)?

Some things to note (that hopefully won't distract):
  • All pipes are 2"
  • The macerating toilet (E) has its own vent system, so that's a different setup
  • Because everything has to drain down into the macerating tank, the shower base will be raised on a 2x6 or 2x8 platform
  • F and G point out the bottom sills of two walls that will go up (once I figure out the drain lines) to bring everything out 3-1/2" (to give me space to run the plumbing without chopping up the load-bearing exterior walls and to give more room to work.
  • Ignore the mis-fitting joint at D. I got a 2" x 1-1/2" by mistake and will get the right part later.
  • The green bars at H and I represent the walls that will be built - this is a corner shower.
So, would the vent at A allow the shower to drain properly?

Bathroom Drainage.jpg


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Victor, MT
The trap arm between the shower (C) and the vent (D) cannot step down the way you show it because it creates an "S" trap.
Hey, wait a minute.

This is awkward, but...

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