how do I get my NPT connections to not leak

[mike69440]

Loctite PST 545 or 547 if I remember correctly, pipe sealant that comes in a tube.

Use this
LOCTITE 542 Thread Sealant - Henkel
PST 545 or 547 only rated to 2000 Psi

 

[Oldpath05]

This says Loctite 545 is 10,000 psi>>> LOCTITE Pipe Thread Sealants,5mL,Bottle,Purple - 5A237'|'54531 - Grainger

 

[mike69440]

This says Loctite 545 is 10,000 psi>>> LOCTITE Pipe Thread Sealants,5mL,Bottle,Purple - 5A237'|'54531 - Grainger

I know the White paste stuff said something like 13746 pacal or 2000 Psig.

 

[bob 59912]

Pages 141 to 149 of the Henkel/Loctite "Adhesive Sourcebook 2017 Volume 20" lists the specifications for Tread Sealants. After 24 hour cure time:

White Paste - Loctite 565 and 567 - Pressure resistance 10,000 psi
White Semi-Solid - Loctite 561 - Pressure resistance 10,000 psi


Pages 133 through 140 covers Thread Lockers

 

[mike69440]

Pages 141 to 149 of the Henkel/Loctite "Adhesive Sourcebook 2017 Volume 20" lists the specifications for Tread Sealants. After 24 hour cure time:

White Paste - Loctite 565 and 567 - Pressure resistance 10,000 psi
White Semi-Solid - Loctite 561 - Pressure resistance 10,000 psi


Pages 133 through 140 covers Thread Lockers

Right on the 1.69 oz tube of Loctite 565 I have in my hands. (For ULC Listing) "For use on threaded joints of metal pipe handling natural gas and methane gasoline and petroleum oils, propane and butane pressures not exceeding 13790 Kpa. 2000 psi) Compound not to be applied below 15C.

(For UL Listing) 565 is rated to 300 psig. So while 565 may be rated by Henkel Loctite to 10KSI, the agency ratings are lower.

Anyways, the 542 stuff is holding 5000 psig on straight threads.

I like the 565 stuff for water and gas pipe more than Teflon tape. If you use tTeflon tape make sure it is good quality and thick.

 

[bazman]

It sounds counter intuitive, but it is possible to over tighten these fittings and distort the threads. Its better to tighten them just a little snug, then tighten just a little more at a time if they happen to leak.

Yes exactly. NPT fittings create a mechanical seal on the threads, so if the threads get distorted in any way the seal is shot. I'm a big believer in the method you mentioned, KYErik. Tighten just a little bit at a time.