I am putting in a bar sink in my basement. The drain pipe is already leading into one of the main stacks that is coming from the upstairs; the bar sink is literally being installed about 2 feet away from the stack. This stack already has a toilet, sink, shower, and washing machine hooked up to it from the upstairs, with proper venting on all appropriate drains. Do I need to add a vent to my bar sink plumbing (like a Studor mini vent) underneath the counter, or does the venting for the fixtures hooked up above it work for this?