An NPT connection stands for National Pipe Thread, and the connection utilizes a male threaded adapter that connects with a female threaded adapter to create a seal. The connection works by the male adapter stretching out the female fitting to create a strong enough force to hold the two pieces together.
With NPT connections, it is important to note that poor lubrication and over-tightening can cause damage to the threads. When using a lubricant, be sure not to use too much, as it can leak out of the connection. Other common connections include:
- BSPT - A British Standard Pipe Thread connection works like an NPT connection, utilizing the pressure of the male and female fittings, but the angle on BSPT threads is 55 degrees as compared to 60 degrees on NPT threads. These connections also require a thread sealant to ensure a proper seal.
- BSPP - A British Standard Parallel Pipe uses a parallel thread design with a bonded seal ring to create the seal. These connections look a little different from the others, as the male fitting is longer, and they use a copper crush washer seal ring. The seal ring fits between the male and female fittings, and as the two fittings come together, the seal is squeezed into place, creating the seal. This type of threaded connection does not require a thread sealant, as the seal ring does the work to create the proper seal.