If you are getting air coming out of the AAV when water runs down the other (double sink, washtub sink, mudroom sink) drains, then there is a pressure buildup between where all these drains connect together, and the vent pipe itself. I'd run a snake through all the lines, past where they all connect to the drain line running under the house (to the main drain line if possible). There is likely a bunch of greasy gunk somewhere partially blocking the pipe. I use a product named Drain Care to prevent these issues. Its contains bacteria that eat grease/soap residue, and die when they run out of stuff to eat. Breaks up the gunk, and you can then flush the drain nicely. Claims to be safe for all pipes and septic systems as well.
Gonna have to get me some of this stuff just to avoid any future problems! Sounds like the same concept as Rid-X, y'all think that stuff really works and keeps the septic system healthy??? Stupid question for the OP, any chance the p trap in that island sink barely had water in it from non-use and that's causing the gurgling??
it's 2:1 soda to vinegar Hot water to rinse helps too https://crunchybetty.com/clean-your-drains-baking-soda-vinegar/ found this link quickly and it is basically what we do a small funnel can help to get the powder where you want it to go, other wise it is a pita to get it in the drain
Hi BrianC636, I just happend to see your post and would like to ask if you already solved your problem. Currently I have the same issue as you had, and am looking for a proper solution.