Proper use of an air admittance valve?

Should an air admittance valve be used in this application? I guess it serves the floor drain? See attached photos.





Craig, I’ve never seen a floor drain that close to the main stack, or an AAV used like that. My guess is that it was added to prevent the sudden rush of water from a toilet flush from sucking the trap dry. What it won’t prevent is the trap drying out from evaporation and a trap primer might be needed (or at least a good idea).

While it looks like it might work, the set-up is unusual enough that I think I’d be recommending a licensed plumber evaluate the purpose, function and conformity.

It seems like the plumber is instead of using a normal vent is using an AAV for the floor drain like you said. I’m not sure if this is code? It’s not normal. If there is a sewer back-up it might clog this AAV.

Maybe it’s fine???

Another red flag on this particular inspection is price stickers from Home Depot on most of the drain line parts. House was built 3 years ago. I don’t know any full time plumbers that would pay Home Depot prices to plumb an entire home.

If nothing else, I would call it “suspect.”

**P3114.4 Location.
**Individual and branch air admittance valves shall be located a minimum of 4 inches (102 mm) above the horizontal branch drain or fixture drain being vented. Stack-type air admittance valves shall be located a minimum of 6 inches (152 mm) above the flood level rim of the highest fixture being vented. The air admittance valve shall be located within the maximum developed length permitted for the vent. The air admittance valve shall be installed a minimum of 6 inches (152 mm) above insulation materials where installed in attics.

This is very wrong!


In my state the air admit. valve is only suppose to be used as a last resort, with the inspectors permission. This was probably the easiest way rather than the only way. As the code said, as long as it meets the hieght requirements above the trap it should work but I would be willing to bet there was a better way. Home depots and stores like these look at these valves as the answer to all venting. This would have been a little better if they would have extended it up to the ceiling, it wouldn’t look so suspect.