I am seeing more of the air vents under sinks that make a remodel easier by not running a vent up through the roof. I try to explain to the client that this helps to vent, but has moving parts with a spring and a seal that over time can wear out and fail. A comment about monitoring the function of that sink venting could be helpful for the future.
Daryl Troute
Note: The one in your photo is not installed properly. Also note: they are not allowed in many areas… check with your local AHJ and their rules for compliance.
Everything in your home wears out over time as longs as they are accessible (which is also required), they are easy to change and not expensive. Should be installed as high as possible. They are widely allowed here and regularly used. Frequently just the main line is vented to the exterior on new builds here. No holes in the roof.
What’s not right about that installation?
Too low above the horizontal run, should be min. 6 inches, and local wants it as high as it will go… think “high loop”.
I always see 4" http://www.studor.net/aav-questions#q7
…or **6 inches **for the full size valve…
Could be my local standardized it at 6 inches for all. As always, check with your local AHJ for your area.