Thure, 
Teflon tape is typically only used to seal threads. You wrap it around the threads before your screw them together (i said screw). If you are trying to seal a tube going thru a hole, a stopper would be your best bet. Even better would be a bulkhead (weldless) fitting that would give you threads on the inside to connect to your manifold. Here are some weldless fittings
If you are crafty, you can make your own weldless fitting with a nipple, washers, orings, and a valve.
				

