American National Standard Pipe Thread standards, often called National Pipe Thread NPT 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, pressuretight 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. Features. Filter Long Adhesive Drain Tee. Made with high quality materialSpecifications. Size 1.5 NPT