Not a direct fit. Joining 1" NPT (National Pipe Taper) to 1" BSP tapered (R1 / BSPT) needs a 1 NPT to R1 BSP tapered adapter. Sealing method, the real-world trap, and the exact adapter to buy.

Updated 05 September 2026.

HoseFitFinder / Every thread and fitting standard

Connect 1" NPT (National Pipe Taper) to 1" BSP tapered (R1 / BSPT)

How to join 1-11.5 NPT and R1, and what stops it leaking.

Needs adapter
End A
1" NPT (National Pipe Taper) (1-11.5 NPT)
Seals on on the thread flanks with PTFE tape
via adapter
End B
1" BSP tapered (R1 / BSPT) (R1)
Seals on on the thread flanks with PTFE tape or paste
Adapter needed1 NPT to R1 BSP tapered adapter

Not a direct fit. Joining 1" NPT (National Pipe Taper) to 1" BSP tapered (R1 / BSPT) needs a 1 NPT to R1 BSP tapered adapter.

The adapter to buy

Shop 1 NPT to R1 BSP tapered adapter on AmazonaffiliateFind 1 NPT to R1 BSP tapered adapter on eBayaffiliate

1 NPT and R1 BSPT are both tapered 1 inch threads, which fools people into forcing them together, but the flank angle differs: 60 degree on NPT, 55 degree on BSPT. They cannot seal against each other, so an NPT-to-BSP-tapered adapter is the correct fix.

Both being tapered at 1 inch is the trap. Same taper, wrong flank angle: the joint starts smoothly then leaks. Use the adapter, not extra tape.

Related connections

1" NPT (National Pipe Taper)1-11.5 NPT1" BSP tapered (R1 / BSPT)R12-1/2" NH fire hose thread (NST) to 1" NPT (National Pipe Taper)adapter1" BSP parallel (G1 / BSPP) to 1" BSP tapered (R1 / BSPT)adapter1" NPT (National Pipe Taper) to 1" BSP parallel (G1 / BSPP)adapter1" NPSH straight hose thread to 1" NPT (National Pipe Taper)adapter

Questions and answers

Connect 1" NPT (National Pipe Taper) to 1" BSP tapered (R1 / BSPT)?

Not a direct fit. Joining 1" NPT (National Pipe Taper) to 1" BSP tapered (R1 / BSPT) needs a 1 NPT to R1 BSP tapered adapter.