I need help on this please. I am only focusing on the DWV here.
This was in 1930’s remodeled house laundry room.
Is it OK to have an AAV in a laundry room?
If it is OK, would you call the machine machine trap and S-trap as there would be no risk of siphoning with the AAV right there? Or would you say there is a risk because the AAV is a mechanical device which can/will fail?
Technically it is still an S-Trap, subject to losing the trap seal due to rushing water through the trap. Fast moving water suddenly stopping will continue its rapid draining, risking not enough water left in the trap to form a seal.
It isn’t all about the venting.
Note: adding 1-2 inches of piping to the horizontal plane will break the S-Trap.