Kitchen Sink Issues

[wtj104]

The setup: ~10yr old house, I have a kitchen with a double sink under a window. Also a small sink in the island across from it. We're getting gurgling from the right side of the double sink after water is run in the double sink, or while the dishwasher is draining into it.

Here is the setup of the double sink plumbing during construction:

View attachment 41889

Each sink has a P trap and the right side has the connection to the dishwasher:

Both P traps are clean, and I've tried sticking a snake down both drains to no avail.

The problem wasn't there initially when the house was new, so I'm assuming this is due to a blockage somewhere? Is it most likely that something is partially blocked further down the main drain stack than I got with the snake? Also, how exactly is the loop vent setup on the double sink supposed to work? It kind of confuses me when I think about troubleshooting the problem.

 

[Plumber69]

Well to start your loop vent is wrong

 

[Sponsor]

 

[Terry]

You can add an AAV to fix that. Some new homes around here are installing the AAV and leaving off the roof vents.
You don't have a proper Island vent there.

Both of these have vents through the roof.

 

[wtj104]

Thank you!

Can you elaborate on what they did wrong with this loop vent? I'd like to understand better how it SHOULD be and/or what they thought they were doing with the loop when the put it in.

Is the loop supposed to extend under the floor over to the next drain section that has a real roof vent (The nearby laundry room utility sink would be the next fixture that does.)

And to fix it, adding one AAV behind either of the two P traps should do it, correct?