What type of threads should threaded fittings in standpipe systems have?

• A. National Pipe Thread (NPT)
• B. British Standard Pipe (BSP)
• C. Metric threads
• D. American Threaded Standard (ATS)

Answer: (A)

Threaded fittings in standpipe systems are specified to use National Pipe Thread (NPT). This tapered thread design seals as the joint is tightened, typically with pipe thread sealant or PTFE tape, which is essential for preventing leaks under the system’s operating pressures. Using the NPT standard ensures compatibility between fittings from different manufacturers and aligns with NFPA 14 expectations for North American installations, promoting reliable performance and maintainability.

Other thread types, such as British Standard Pipe (BSP), metric threads, or less common standards, are not typically used in U.S. standpipe installations. They would require adapters and can compromise sealing and code compliance.