What is the standard pipe thread commonly used in the United States?

The standard pipe thread commonly used in the United States is National Pipe Tapered Thread, abbreviated as NPT. This threading system is designed to create a pressure-tight seal when two pipes are screwed together. The taper in the threads allows the threads to wedge against each other as they are tightened, enhancing the sealing capability and preventing leaks in fluid systems.

NPT threads have specific dimensions and angles defined by the American National Standards Institute (ANSI), making them suitable for various plumbing and piping applications in both residential and industrial settings. Understanding NPT is crucial for boilermakers and others working with piping systems, as it ensures compatibility and proper sealing in a variety of installations.

Other types of threads mentioned, such as BSPT (British Standard Pipe Taper) and USP (which is not a recognized standard for pipe threading) are used in different regions or contexts and may not be suitable for use in the U.S. CPT does not represent a commonly recognized thread standard in pipe applications.