You may get several opinions on this. I use thread tape, alot of the old timers I grew up around did not. In theory, with NPT threads you don't need it. I like it, especially with something like a petcock because it allows you to clock the fitting where you want it. You don't need it tight. Hand tight and then a .25 turn or so is plenty. Another thing I do is: I only wrap the top 3/4 or so of the threads. That way there is no chance of getting tape into the cavity.