Wrap It Twice
Ever found one of those pipe connections that just seemed "loose" or that wouldn’t turn down tight? Maybe you’re dealing with old, bunged up threads and don’t want to deal with the hassle of re-plumbing (who does?). Well here’s a tip for you that just might make those sloppy/bunged-up threads hold pressure:
Double dope it!
First, wrap the male thread end with TFE tape. Do it once or twice (or even thrice) depending on just how sloppy the threads are. Then, on the female side, goop the threads up with a thin, even coat of Rector-Seal®.
Mate them and turn down tight.
If this doesn’t solve your problem you’ve got bigger problems! You’re going to have to either repair the damaged threads (sometimes possible) or remove the pipe/fitting that is damaged and replace it.
The threads of plastic pipe and fittings are really susceptible to damage. It’s also easier to stop leaks in plastic pipe with this little trick because the threads are softer.
While no trick is perfect, you’ll likely find this one really handy time and time again!
Happy plumbing!