Using AAV in bathroom: help decyphering the code

[Michael M]

I'm in the middle of re-modelling a bathroom, and trying to figure out what my venting options are. The original plumbing was definitely not up to any recent code.

Specifically, I'm trying to figure out the part of the IPC that talks about "branch-type air admittance valves". The IPC has the following to say:

Section 918.3.1 Individual and branch-type air admittance valves shall vent only fixtures that are on the same floor level and connect to a horizontal branch drain.

Check! My fixtures are on the same floor level and connect to a horizontal branch.

Section 918.4 Individual and branch-type air admittance valves shall be located a minimum of 4 inches (102 mm) above the horizontal branch drain or fixture drain being vented.

Here is where I'm confused. It sounds like I can put in a branch-type air admittance valve below floor level, as long as it's at least 4 inches above the horizontal branch drain. Is this correct? It seems odd to me that the code would require stack-type AAVs to be above the flood level rim of the highest vented fixture, individual-type AAVs to be above the fixture drain, but let horizontal branch AAVs be so low down. Am I misunderstanding something?

 

[ye4jim]

Related question:

Can a bathroom sink and shower share an AAV as shown? Note I forgot to show the p-trap for the shower, but it's there?

How about if the shower was downstream of the sink ?

Thanks!