That union is already coming in handy!

I've always used teflon tape on the threaded connections, but if Pentair says not to, so be it.

When a pump's discharge port gets to be a PITA to stop the drip, I'll use an o-ring to help seal the threads. You may be able to do this without having to fully unscrew the male adapter (but it's best to reapply the pipe dope).

Good luck with the fix!