Quote Originally Posted by SunnyOptimism View Post
If you do get it off, it's always best to use liquid teflon thread sealant, not teflon tape, when closing it back up again.

I should have elaborated a bit as PoolClown is correct, on a threaded union, the threads don't do any sealing and hand tightening is all you need.

So why use thread paste? I do it because I find that, in my climate, threads will get locked up with lots of dust, sand and gunk. Teflon thread paste doesn't solidify or cure but stays as a viscous fluid. So it makes taking the union on and off very easy and it keeps the union threads from getting locked up. Since it's PVC, you can't spray LiquidWrench or any kind of hydrocarbon-based thread compound on it.

The teflon thread paste is not at all necessary, just a quick little trick I learned long ago....