NPT fittings leak in a hard plumbed system

Systems, Gear, & DIY
1

Thought I’d reach out to those of you who have built hard plumbed systems for some advice.  I’ve got a single tier, HERMS system coming together, but I’m really struggling to get the NPT fittings (valves, elbows etc) around the pump to seal properly.  I have not problem with my compression fittings (Swagelok) since I’ve worked on that stuff for years, but NPT is new to me, and frankly rather frustrating.  The real challenge is getting it to seal, and have everything line up.

It’s 1/2" stainless steel NPT, right now I’m using regular white PTFE tape.  I’m about to try the triple density pink tape which is ASTM rated for 1/2" fittings and above.  Any other suggestions from those of you who’ve been through this already?

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Thanks!

2

NPT fittings have to have Teflon tape or plumbers putty to seal.  You can use regular plumbers Teflon tape or gas Teflon tape. Wrap it around pine 3 to 6 times and you should be good.

Good luck.

3

The only time I’ve had problems with NPT fittings sealing with teflon tape was when I wasn’t careful and some of the tape overlapped at the end of the fitting so that some of the tape wrapped over to the inside of the fitting.  Once I re-wrapped the threads, the leak went away.