Not a direct fit. Joining 2-1/2" NPSH straight hose thread to 2-1/2" 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 2-1/2" NPSH straight hose thread to 2-1/2" NH fire hose thread (NST)
How to join 2-1/2-8NPSH and 2-1/2-7.5NH, and what stops it leaking.
Not a direct fit. Joining 2-1/2" NPSH straight hose thread to 2-1/2" NH fire hose thread (NST) needs a straight NPSH hose-to-gasket-sealed NH hose adapter.
The adapter to buy
2-1/2-8NPSH and 2-1/2-7.5NH are both straight gasket-sealed hose threads at the same nominal size but to different standards (8 versus 7.5 threads per inch, 72.16 mm versus 77.94 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 2-1/2" NPSH straight hose thread to 2-1/2" NH fire hose thread (NST)?
Not a direct fit. Joining 2-1/2" NPSH straight hose thread to 2-1/2" NH fire hose thread (NST) needs a straight NPSH hose-to-gasket-sealed NH hose adapter.