True or False: Thru-hull fittings primarily use NPS threads while ball valve assemblies use NPT threads.

Thru-hull fittings primarily utilize National Pipe Straight (NPS) threads because these fittings are designed to provide a watertight seal without the need for tapering, which is essential for preventing leaks at the point where water enters or exits a vessel. NPS threads are straight and designed for use with sealing methods such as O-rings or gaskets, which is ideal for the rigorous conditions these fittings face in marine environments.

On the other hand, ball valve assemblies typically use National Pipe Tapered (NPT) threads. NPT threads are tapered, allowing for the threads to mesh tightly together and create a durable seal as the fittings are tightened. This tapering is significant in applications like ball valves where a robust seal is necessary to prevent leaks under pressure.

The distinction between the types of threads and their applications is critical for ensuring proper installation and function in marine plumbing systems. Thus, the assertion that thru-hull fittings primarily use NPS threads while ball valve assemblies use NPT threads is accurate.