What is NPT thread?

NPT stands for National Pipe Taper, which is a U.S. standard for tapered threads used on pipes and pipe fittings for the purpose of sealing. NPT threads are designed to provide a leak-free seal when used with a thread sealant, such as Teflon tape or pipe dope. The taper on an NPT thread allows it to form a seal when mated with another tapered thread.

Key characteristics of NPT threads include:

1. Taper: The outside diameter (OD) of the thread decreases slightly from the start to the end of the thread. This taper, typically 1/16 inch per inch, helps in creating a tight seal as the parts are tightened together.

2. Thread Angle: NPT threads have a 60-degree thread angle, similar to many other screw thread standards, but the shape and spacing are specifically designed for pipe connections.

3. Pitch: The pitch (number of threads per inch) varies depending on the nominal pipe size. For example, a 1/8-inch NPT has 27 threads per inch, while a 2-inch NPT has 11.5 threads per inch.

4. Seal: To ensure a proper seal, a thread sealant must be used. Without it, there's a high likelihood of leaks because the metal-to-metal contact alone does not create a sufficient seal.

5. Hand Tightening: NPT threads should be hand-tightened first, then given additional turns with a wrench to achieve the proper seal. The number of additional turns depends on the size of the fitting and the material; generally, 1.5 to 3.5 turns beyond finger tight are recommended.

NPT threads are commonly used in plumbing, hydraulics, and pneumatic systems, among others, where a secure, leak-proof connection is required. There is also a dry-seal version called NPTF (National Pipe Taper Fuel) that is designed to provide a mechanical seal without the need for a separate sealant, although some applications may still require a sealant for added security.

For any other questions related to NPT fittings or the rest of our product catalog, please contact us.