what are the differences between NPT and NPTF?

NPT and NPTF threads are both commonly used tapered pipe threads in plumbing and piping systems, but they have some key differences:


  • NPT (National Pipe Taper): Requires a sealant, like Teflon tape or pipe dope, to create a leakproof connection. The threads themselves don’t provide a perfect seal, so the sealant fills in any gaps and prevents leaks.
  • NPTF (National Pipe Taper Fuel): Designed for dryseal applications, meaning they create a leakproof seal without the need for additional sealant. The threads are slightly different than NPT threads, with flatter crests and valleys that provide a tighter fit and seal.

Thread profile:

  • NPT: Has a wider range of crest tolerances compared to NPTF. This means there can be more variation in the shape of the thread peaks.
  • NPTF: Has tighter crest tolerances, resulting in a more consistent and precise thread profile. This contributes to the better sealing capabilities.


  • NPT: Used for general-purpose piping applications where leaks are not a major concern, such as water or air lines.
  • NPTF: Used for applications where leakproof connections are critical, such as fuel lines, gas lines, and hydraulic systems.


  • NPTF fittings can usually be screwed into NPT threads, but the seal may not be as good without sealant.
  • NPT fittings should not be used in NPTF applications without sealant, as leaks are likely to occur.

Here’s a table summarizing the key differences:

Feature NPT NPTF
Sealing Requires sealant Dryseal (no sealant needed)
Thread profile Wider range of crest tolerances Tighter crest tolerances
Applications General-purpose piping Leakproof applications
Interchangeability NPTF can fit NPT, but seal may be compromised NPT should not be used in NPTF without sealant

I hope this explanation helps! Let me know if you have any other questions.

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