Teflon tape is used to help eliminate leaks in copper or PVC pipes in a fluid system. There are different thicknesses of Teflon tape, and they all do well as long as you make sure you have adequate tape on the threads.
Direction of Wrap
When wrapping Teflon tape around the male edge of the pipe it is important to wrap the tape in a clockwise direction. To do this, hold the pipe in your left hand, or have the pipe to your left side if it is a mounted pipe. Put the tape on the threads and run the tape around the threads over the top of the pipe.
Amount of Wraps
Depending on the density of the tape, you may wrap the tape two to three times. If you have a thicker (4mil) density, then two wraps should be adequate. However, if you are using a 2 mil or less density tape, then at least three wraps will ensure that the seal is sound.
Make sure that the tape wrap is tight enough to adhere to the shape of the threads. When you attach the two sides of the pipe, make sure that no tape has overlapped on the open end of the pipe.