When I remodeled my kitchen a year ago, I installed a beautiful Blanco farm sink. It's always been a bit slow to drain, but over the last month or so has gotten bad enough to where I have to plunge it to get it to drain. All of the other drains in the house run fine.

Since then, I've read that I should have lowered the height of the drain coming out of the wall. Obviously, I'd prefer not to, but if I have to , I will.

Yesterday, I installed an AAV. At first, it worked great - water was draining like crazy. After the first one, performance now varies from good to no drainage. As a test, I removed the vent valve completely and the water still stood still!

The drain line is 9 1/2" below the bottom of the sink, and the trap height is 5 1/2" top to bottom.

Any ideas would be appreciated. Thanks!

You may just have a stopped up drain line which would have nothing to do with the drain and trap under the sink.

unscrew the AAV and run a snake wire down..once the water starts to move. trickle a little water as the snake is spinning.