Thread Sealant - Teflon Tape VS Paste
Based on an article from plumbertip.com
Teflon tape is a quick and clean way to seal threads in most applications. When applying Teflon tape, care must be taken to apply the tape correctly or leaking may still occur. You should wrap the thread 2-3 times around the threads in a counter-clockwise direction so that the tape doesn't bunch up when it is screwed into the pipe. Do not over-tighten, as this may cause the tape to become thin or break in spots, while under-tightening may allow water through.
For professional, long-term or industrial applications, Teflon paste, although messy and more difficult to apply, will provide a more reliable seal that won't leak if the plastic pipe distorts over time. Teflon paste should be applied to both the male and female threads.