Originally Posted By: Beer Belly

FYI:
I don't think that he threads are the seal. They are just meant to hold the male/female sealing pieces together.



Exactly..........

And teflon tape isn't a leak stopper, it is thread lubricant. Lubrication of tapered threads (such as npt pipe) allows for deeper engament which in turns allows them to reach the point where they do not leak.