3" NH fire hose thread (NST) (3-6NH)

Used on: US fire hose, standpipes and large transfer lines at 3 inch.

The 3 inch NH (National Hose / NST) thread runs 6 TPI on a 3.623 inch (92.02 mm) outside diameter and seals on a rubber gasket in the female swivel, as defined for fire connections in NFPA 1963. It is not a pipe thread and will not mate with an NPT of the same nominal size without an adapter.

Quick-connect click fittings from Hozelock, Gardena and Karcher are proprietary and do not interchange. They all sit on top of a standard thread underneath, so the reliable way to move between brands is to adapt at the threaded tap or hose-end fitting, then use each brand's own connector above it.