American National Standard Pipe Thread standards, often called national pipe thread standards for short, are U.S. national technical standards for screw threads used on threaded pipes and pipe fittings. They include both tapered and straight thread series for various purposes including rigidity, pressure-tight sealing, or both. The various types are each named with a symbol and a full name; examples of the symbols include NPT, NPS, NPTF, NPSC, and others.
Abbr Shorthand expansion Full name Comment NPT National pipe taper American National Standard Taper Pipe Thread Tapered for sealing, often without any thread sealant; for connections in nearly every type of service NPS National pipe straight American National Standard Straight Pipe Thread For rigidity; sealable only with sealant; sometimes male straight enclosed by female tapered for low-pressure sealing NPSC National pipe straight–coupling American National Standard Straight Pipe Thread for Couplings For general couplings NPSF National pipe straight–fuel Dryseal USA (American) Standard Fuel Internal Straight Pipe Thread Internal only, straight NPSH National pipe straight–hose American National Standard Straight Pipe Thread for Hose Couplings For hose couplings NPSI National pipe straight–intermediate Dryseal USA (American) Standard Intermediate Internal Straight Pipe Thread Similar to NPSF but slightly larger; internal only, straight NPSL National pipe straight–locknut American National Standard Straight Pipe Thread for Loose-fitting Mechanical Joints with Locknuts For use with locknuts NPSM National pipe straight–mechanical American National Standard Straight Pipe Thread for Free-fitting Mechanical Joints For various rigid mechanical uses NPTF National pipe taper–fuel Dryseal USA (American) Standard Taper Pipe Thread For dryseal connections in nearly every type of service, especially fuel connections NPTR National pipe taper–railing American National Standard Taper Pipe Thread for Railing Joints For railings PTF-SAE SHORT Pipe taper, fuel, SAE, short Dryseal SAE Short Taper Pipe Thread Named after SAE International; similar to NPTF but one turn shorter
