I am installing a bathtub in our basment and have broken up the floor for the tub drain. The 2″ drain line will run 30″, make a 90 degree turn and then run 5′ over to the vented drain pipe. Do I need to install a vent closer to the drain of the tub itself. The books say that for a 2″ pipe, you should be no more than 5′ away from a drain, so my distance of 7.5′ is more than the spec, but not very much. And if I do need to vent closer. There is a horizontally running vent pipe in the ceiling above this tub. Can I go up the wall next to the tub and connect into this?