Which type of threads are used to create a pressure tight and watertight seal?

NPT (National Pipe Thread) threads are specifically designed to create a pressure-tight and watertight seal in piping systems. The tapered design of NPT threads allows them to create a mechanical seal upon tightening, which compresses the threads against each other and fills any gaps, preventing leaks. This feature makes NPT threads particularly suitable for applications involving fluids and gases under pressure.

The taper also helps to ensure that the connection is progressively tighter as it is screwed in, which is critical for maintaining the integrity of a seal in high-pressure applications. NPT threads are widely used in plumbing, gas lines, and various industrial applications for this reason, ensuring safety and effectiveness in sealing.

Other thread types, while employed in various applications, do not typically achieve the same level of performance in creating a tight seal for pressurized systems as NPT threads.