BSPT Pipe Thread vs. NPT Pipe Thread
Comparing 2 standards across 8 specifications. 7 key differences identified.
BSPT (British Standard Pipe Taper), designated as the 'R' series under ISO 7-1 and EN 10226, is a 55° Whitworth pipe thread with a 1:16 taper rate. Commonly used in European, Commonwealth, and Japanese plumbing systems, external tapered R threads mate with either internal parallel Rp threads or internal tapered Rc threads to achieve pressure-tight joint sealing.
NPT (National Pipe Taper) is the standard North American tapered pipe thread governed by ANSI/ASME B1.20.1. Featuring a 60° thread flank angle and a 1:16 taper rate (0.75 inches per foot), NPT achieves sealing through flank wedging and deformation, requiring PTFE tape or pipe sealant to prevent spiral leak paths.
Specification Comparison Table
8 Parameters| Parameter / Spec | ||
|---|---|---|
|
Standard Governing Body
|
ISO 7-1 / EN 10226-1 / BS 21 / DIN 2999 | ANSI / ASME B1.20.1 |
|
Thread Form & Flank Angle
|
55° Whitworth with radiused crests and roots | 60° symmetric truncated V-thread |
|
Taper Ratio
|
1:16 (0.75 in/ft or 1° 47' with centerline) | 1:16 (0.75 in/ft or 1° 47' with centerline) |
|
Common Pitches (TPI)
|
R 1/8": 28 TPI | R 1/4"-3/8": 19 TPI | R 1/2"-3/4": 14 TPI | R 1"-2": 11 TPI | 1/8": 27 TPI | 1/4"-3/8": 18 TPI | 1/2"-3/4": 14 TPI | 1"-2": 11.5 TPI |
|
Sealing Mechanism
|
Metal-to-metal flank wedging + jointing paste/PTFE tape | Thread flank interference fit + PTFE tape / anaerobic sealant |
|
Primary Geographical Region
|
Europe, United Kingdom, Japan (JIS B 0203), Commonwealth | United States, Canada, and Mexico |
|
Thread Designation
|
R (Male taper), Rc (Female taper), Rp (Female parallel) | — |
|
Max Working Pressure @ 23°C (73°F)
|
— | Up to 5,000–10,000 PSI (dependent on pipe schedule/fitting) |