Not a direct fit. Joining 2-1/2" NPSH straight hose thread to 2-1/2" NPT (National Pipe Taper) needs a 2-1/2 NPSH to 2-1/2 NPT 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" NPT (National Pipe Taper)
How to join 2-1/2-8NPSH and 2-1/2-8 NPT, and what stops it leaking.
Not a direct fit. Joining 2-1/2" NPSH straight hose thread to 2-1/2" NPT (National Pipe Taper) needs a 2-1/2 NPSH to 2-1/2 NPT adapter.
The adapter to buy
2-1/2 NPSH is a straight (parallel) hose thread and 2-1/2 NPT is tapered, so a 2-1/2 NPSH hose will not seal into a 2-1/2 NPT pipe port despite the matching nominal size. An NPSH-to-NPT adapter presents a tapered male for the pipe and a straight female for the hose.
The straight-into-tapered mistake weeps because the flanks never fully mate. Fit the adapter rather than forcing the 2-1/2 hose coupling onto a pipe thread.
Related connections
Questions and answers
Connect 2-1/2" NPSH straight hose thread to 2-1/2" NPT (National Pipe Taper)?
Not a direct fit. Joining 2-1/2" NPSH straight hose thread to 2-1/2" NPT (National Pipe Taper) needs a 2-1/2 NPSH to 2-1/2 NPT adapter.