Common types of U.S. fire hose thread include National Hose Thread (NH) or National Standard Thread (NST), National Pipe Straight Hose Thread (NPSH, NPS) and Garden Hose Thread (GHT).

NH / NST Threads

The most common thread type in use by United States Fire Departments today is National Hose (NH) or National Standard Thread (NST). It is often referred to as “fire hose" thread. NH, NST and NHT are different abbreviations for the same common thread.

NH / NST hose couplings will only connect to fittings, nozzles or other hoses with the same thread. National Hose thread is considered a “straight” thread, which means the grooves are consistently-spaced from tip to collar.

The hose threads seal with the use of a gasket located inside the female end of the hose. This presses against a male coupling. The threads are designed to hold the two fittings together. The size of a NH thread refers to the inside diameter of the waterway on the male coupling. A 2 1/2" NH male = 2 1/2" waterway.

•    National Hose also known as National Standard Thread.
•    The female threads will only connect to a male NH.
•    The male threads will only connect to a female NH.
•    NH is the most common thread in the fire service.
•    NH fittings seal with included gasket.

NPSH Hose Threads

Fire hoses with National Pipe Straight Hose Thread (NPSH or NPS) has the same threads per inch (TPI) as National Pipe Thread (NPT) but the threads do not taper. This allows for a female coupling to thread onto a compatible NPT male fitting, without creating a permanent connection. 

A male NPSH fitting will NOT connect to a female NPT. Male fire hose couplings with NPSH threads will require a nozzle with NPSH threads.

Female fire hose couplings with NPSH thread will only connect to a PVC pipe, metal pipe, or couplings with NPSH or NPT threads. Fittings connected together by NPT require a sealing agent like pipe cement or teflon tape to make the seal a permanent connection.

•    National Pipe Straight Hose
•    The female threads will only connect to a male NPT or NPSH.
•    The male threads will only connect to a female NPSH.
•    A male NPSH WILL NOT thread into a female NPT.

Garden Hose Threads

Garden Hose Threads (GHT) are similar to NST and NPSH, sealing the connection with a gasket in the female coupling. A typical garden hose may have an inside diameter of 5/8" or 3/4", but the fitting on the ends of the hose will usually be GHT.

GHT is not compatible with NPT. For example, 3/4" GHT is NOT the same as 3/4" NPT.

•    The female threads will only connect to a male GHT.
•    The male threads will only connect to a female GHT.
•    It WILL NOT connect to 3/4" NPT or NPSH threads.
•    GHT fittings seal with included gasket.