Wrap Teflon Tape in the Right Direction

The Problem

A threaded fitting can look perfectly sealed as you thread it on and still leak once it's under pressure. The tape doesn't fail from being skipped — it fails from being wrapped in the direction that unwinds itself as the fitting tightens, and there's no way to see that from the outside once the joint is assembled.

The Technique

1. Face the end of the pipe you're taping.
2. Wrap the tape clockwise around the threads from that view. A fitting's threads tighten clockwise, so wrapping this direction means the fitting's own tightening motion presses the tape into the threads and holds it there.
3. Contour the first wrap to the threads without pulling much tension, then apply three to four wraps with light tension.
4. Pull the tape tight to tear it off, and tuck the loose end down against the pipe.

Wrapped the other way — counterclockwise, facing the pipe end — the tape does the opposite: as the fitting tightens, the motion works against the tape instead of with it, and the tape rolls and bunches instead of sealing. It can look wrapped correctly right up until you thread the fitting on and watch it unravel.