Air Admittance Valve location

We have two photography studios, each with their own kitchen sink. Both sinks have separate drain lines that converge with a Y fitting, then that single pipe goes to a Saniflo pump. One sink has about 15 feet of individual drain line before they merge, the other about 6 feet. There are no AAV's and the sinks gurgle when one is being used. There is very little drain pipe under the sinks so I don't think i can get a valve right after the trap. The pipes are then not accessible until just before they both merge. I think AAV's need to be within 6' of the fixture? I could squeeze one in before the Y fitting (and be roughly within 6') for one sink but that won't help the other right? If I go after the Y fitting, it's still 15' from the other sink which I imagine won't help at all?

The main waste vent comes from the saniflo, could i run a pipe after the Y fitting that ties direct to the waste pipe after the saniflo, would that help at all. I really don't want to start smashing up plaster walls if I can avoid it!

Thanks

 

Please post pictures of the setup. Give us a full view of what is under the sink. http://www.doityourself.com/forum/li...rt-images.html

 

Thanks, These are under the two sinks (one single bowl and the other is a double) and where the pipes meet. The pipe then slopes down to the Saniflo
The Y fitting is capped at one end

 

Put a Tee at the wall and run a pipe up as high as you can then the AAV valve on top.