SpudBlaster15 wrote:Why is everyone going on about epoxy? The OP needs to take a look at the real problem: His threads.
Properly tapped NPT threads should hold the fitting securely without the need for any adhesive. You either drilled the hole too large, threaded the tap through too far, or used the wrong size tap. Figure out the issue, go buy another valve, and redo it properly instead of trying to jury rig a flawed setup with epoxy.
I'm fairly certain I tapped it correctly - used a 5/16 bit, followed by a 1/8 NPT tap and a 1/8 NPT nipple. I think I may have cross-threaded the nipple, though, when I was testing the hole. I think I will retry it with another valve and the JB Weld.
Thanks to all for your help!