Teflon tape is a plastic tape that helps to seal pipe thread fittings and make them easier to screw together. It should only be used on male pipe thread fittings, and should be wrapped two to three times against the grain of the threads.
When installing an irrigation system using PVC threaded fittings you should use two or three wraps of this teflon tape on the male ends. Not only does it help seal against any water leaks it allows for a smooth threading together of parts. Even better it lets you UNscrew parts if needed, now and in the future! If you think we are kidding try for yourself and test with and without................told you! :-)