Venting Bathroom Remodel

[gdude]

Redoing a bathroom and want to avoid drilling through load bearing wall studs for vent piping. Will the sketch below work or do I need to add an AAV to the vanity and/or to the shower?
Any advice is much appreciated.

 

[wwhitney]

You're showing 3 externally trapped fixtures, the lav, the shower, and the tub. Each of those traps needs a vent connection before the trap arm falls more than one pipe diameter.

Your lav is going to have the highest elevation trap. So the only way to vent that is with a connection at that elevation, either an AAV or a dry vent that connects to a vent through the roof.

For the shower and tub, there is the possibility of horizontal wet venting. For that, the trap arm has to connect (as its first connection) to a drain that carries another bathroom fixture that has already been vented (via an AAV or dry vent) and that only carries bathroom fixtures. The wye where the drains connect is the vent for the wet vented trap, and so the elevation difference between that wye and the trap is limited to one pipe diameter of fall.

So in other words, if you rerouted your lav drain so that it hit the tub drain before the tub hits the shower, then that dry vented lav could wet vent the tub. Otherwise you also need an AAV or a dry vent for the tub.

With the distance and configuration shown, as soon as the tub is properly vented, the shower will be properly wet vented (again as long as that 2 ft of shower trap arm is all horizontal).

Cheers, Wayne

 

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[gdude]

Thanks so much, Wayne! Got it! I appreciate the great explanation and quick reply.
Best, Gary