Siphoning trap.... Why?!?

[Lunnybin]

So after two years of use, no problems, the telltale smell arises from the sinks. The master sinks are 20 ft from the stack, hence the AAV, with a tub halfway to the stack on the same line of 2" sch40, proper slope. Snaked the stack and it was clear. Replaced the AAV, despite old one being fine. Still the smell. Any ideas?

 

[frodo]

aav is most likely no good

aav to low
drain to far from vent
to many slip joints [only allowed 1]
not enough hangers
no fall
you used a glue trap instead of a slip joint
need a cleanout.

 

[SHR]

The accordion plastic POS tubing itself is enough to cause odor problems due to waste collecting in those nice pockets.