Talk:National pipe thread

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Split Article[edit]

Would anyone be willing to start a main article for National Pipe Thread Tapered Fine (NPTF), ANSI B1.20.3? There are some oddly cobbled redirects to this article from NPTF and article names starting with NPTF. The chart in this article only covers NPT. Stephen Charles Thompson (talk) 17:57, 30 December 2008 (UTC)

NPTF is National Pipe Thread Fuel

Reference Needed[edit]

Would someone be willing to verify this article information against the ANSI B1.20.1 document and then add this document as a reference? Stephen Charles Thompson (talk) 17:57, 30 December 2008 (UTC) NPT is the acronym for national pipe taper which is 3/4"/ft. NPTF is the acronym for national pipe taper fuel. The threads are the same basic dimension as NPT, but minor differences allow the threads to "bottom out" diametrically which creates a dry fit seal without using any sealing compound or tape that could be compromised by the chemical or thermal properties of the contents contained within the pipes. — Preceding unsigned comment added by (talk) 16:28, 14 April 2013 (UTC)

Article Name[edit]

What is the subject of this article? Is it "National Pipe Thread" or is it "National Pipe Thread Tapered"? The bold text of the article summary does not match the article title. Also, the article title does not appear to be properly capitalized. If the subject is a proper noun then the first letter of each word in the article name should also be capitalized. If you need assistance please contact me. Stephen Charles Thompson (talk) 06:40, 29 December 2008 (UTC)

Should be National Pipe Thread —Preceding unsigned comment added by (talk) 16:05, 18 February 2009 (UTC)

I disagree. In my opinion it should be National Pipe Taper. Otherwise "NPT Thread" is redundant... (like "ATM Machine"). Darr247 (talk) 17:35, 8 October 2013 (UTC)

I would like to point out that:

  • NPT = National Pipe Taper - thread
  • NPS = National Pipe Straight - threads

This article could be about both (and others) since its title implies that it's about all the different types of national pipe threads. — Preceding unsigned comment added by (talk) 17:16, 26 September 2014 (UTC)


How should NPT threads be tightened? I've heard 2.5 turns beyond hand tight for small fittings, 1.5-2 for larger ones, but I don't have a reference for that. Does anyone have a good source on how to install NPT fittings? Evand 19:21, 8 February 2006 (UTC)

The key standard is ANSI/ASME B1.20.1 "Pipe Threads, General Purpose (Inch)". Table 2 of that reference calls for 3 threads of make-up from hand-tight for pipes 2" and under (nominal), and 2 threads for pipes with nominal sizes over 2 inches. --WaldorfSalad 19:40, 31 July 2006 (UTC)

I do wonder if these recommendations for tightening include items made from copper and brass. Many fittings and valves are so made, and I would never tighten such items to the degree that the above chart suggests. Deformation and splitting could occur. {Jack T., long-time plumber.} —Preceding unsigned comment added by (talk) 13:00, 24 May 2008 (UTC)

Repeated use[edit]

It is my understanding that NPT threads should not be assembled / disassembled repeatedly, since the deformation of the threads causes them to wear out over time. I don't have a reference handy for that. Is this correct? Does anyone have a reference either way? Evand 02:29, 2 August 2006 (UTC)

It depends Evand. NPT seals on the thread flanks without the need to deform. If the thread lube prevents spalling they can be reused many times. NPTF crush on the flats, different situation. By all means add some info on reusability when there is a reference for it. Meggar 07:10, 2 August 2006 (UTC)

MPT and FPT[edit]

It looks like MPT and FPT stand for Male Pipe Thread and Female Pipe Thread, not Male Pipe Taper and Female Pipe Taper. Googling on "Male Pipe Taper" (in quotes) turned up one hit - this article! Googling on "Male Pipe Thread" turned up numerous plumbing sites, including, which the paragraph in question was plagiarized from. --Javance 18:29, 2 August 2007 (UTC)

The female thread is not tapered; only the male thread has the taper. Darr247 (talk) 17:40, 8 October 2013 (UTC)

Metric Equivalent?[edit]

Is there a metric equivalent? Roger 21:19, 30 October 2007 (UTC)

Pipe thread sizes table[edit]

Does the outer diameter in the table refer to the base of the threaded portion, not the tapered end? If so, that should be stated after the table title. If you measure the diameter by placing a ruler against the end of the pipe, you are going to get a smaller value.

Steve Wise (talk) 17:46, 3 May 2009 (UTC)

Actually, nominal pipe sizes refer to the inside diameter, which doesn't change whether its outside is threaded or not. Darr247 (talk) 17:43, 8 October 2013 (UTC)

NPT & BSP compatibility[edit]

This important issue is not mentioned and needs inclusion - I have had some difficulty finding someone who knows! My local contacts (Wrexham, N. Wales) advise that up to and inc. 1", NPT and BSP are compatible, but above are not. This needs verifying. Clwydd (talk) 09:40, 22 July 2009 (UTC)

NPT vs NPS[edit]

'NPT' is "National Pipe Taper"

'NPS' is "National Pipe Straight" (a similar thread, without the taper)

Place to consult include: The _SME_Tool_Engineers_Handbook_, ISBN 07-001524-4; _Machinery's_Handbook_, Library of Congress Catalog Card Number: 72-62276.

 I concur... too bad you didn't sign your post with 4 tildes like it says below the Editing Talk box. Darr247 (talk) 17:46, 8 October 2013 (UTC)

Citation needed?[edit]

"The use of tape also helps to limit corrosion on the threads, which otherwise can make future disassembly nearly impossible.[citation needed]"

Is the suggestion that the Teflon (or other plastic) tape preventing corrosion on the fittings can't be taken as obvious, or that a rusted screw in a rusted socket being nearly impossible to remove can't be taken as obvious. I would challenge whoever asked for a citation to provide a counter-example for either case. — Preceding unsigned comment added by (talk) 14:59, 4 April 2013 (UTC)

 Teflon tape seals against leakage... there is no corrosion preventative in Teflon. Just another reason not to use galvanized pipe. Darr247 (talk) 17:55, 8 October 2013 (UTC)