Not a direct fit. Joining 1-1/2" NPSH straight hose thread to 1-1/2" NH fire hose thread (NST) needs a straight NPSH hose-to-gasket-sealed NH hose adapter. Sealing method, the real-world trap, and the exact adapter to buy.
Updated 05 September 2026.
Connect 1-1/2" NPSH straight hose thread to 1-1/2" NH fire hose thread (NST)
How to join 1-1/2-11.5NPSH and 1-1/2-9NH, and what stops it leaking.
Not a direct fit. Joining 1-1/2" NPSH straight hose thread to 1-1/2" NH fire hose thread (NST) needs a straight NPSH hose-to-gasket-sealed NH hose adapter.
The adapter to buy
1-1/2-11.5NPSH and 1-1/2-9NH are both straight gasket-sealed hose threads at the same nominal size but to different standards (11.5 versus 9 threads per inch, 47.7 mm versus 50.55 mm major diameter), so their couplings do not interchange. A crossover adapter joins the two hose standards.
A shared nominal size hides a different pitch and diameter. Match the coupling to its own standard or use the crossover adapter; do not force one swivel onto the other.
Related connections
Questions and answers
Connect 1-1/2" NPSH straight hose thread to 1-1/2" NH fire hose thread (NST)?
Not a direct fit. Joining 1-1/2" NPSH straight hose thread to 1-1/2" NH fire hose thread (NST) needs a straight NPSH hose-to-gasket-sealed NH hose adapter.