I am in the process of redoing my basement, and we've added a shower down there, but in this process, and due to the way my basement is set up, I was unable to tap into the roof vent for my drainage, so I set it up planning to use a studor type vent. Well, the bathroom is done, and upon installing the sink, it drains very slowly, even with the studor vent. I believe the problem is that the vent is below the sink drain because we got one a vanity with the sink that sits on top of the vanity. The studor vent is about 10 inches above the trap under the sink, but like I said, the studor vent is about 4 inches below the drain. If I unscrew the studor vent completely, it drains fine. Any suggestions? It's an odd situation because of my basement setup. Couldn't put it in the wall because I only have 1x4" studs on the wall due to the way everything was in there before we bought the house. Any suggestions?

I hate to say it, but the only way its going to work is to get the studor vent up higher.