NH / NST: The mostcommon thread type in use by fire departments today is NST or National Standard Thread. NST also goes by the initials NH or National Hose. It can even be referred to as NHT or National Hose Thread. But NST or NH is more common these days. NH = NST.
NPSH: National Pipe Straight Hose (NPSH) or Iron Pipe Thread (IPT) has the same threads per inch (TPI) as National Pipe Tapered (NPT), but the thread does not taper. NPSH is a straight thread and seals by a gasket in the female coupling which allows for a swivel, just like NH / NST, which make both ideal for hose couplings. Warning - It will NOT thread into a female NPT pipe. For example, a male NPSH coupling will NOT thread into a female metal or pvc pipe.
