BSPP Pipe Thread vs. NPT Pipe Thread
Comparing 2 standards across 9 specifications. 9 key differences identified.
BSPP (British Standard Pipe Parallel), designated with the prefix 'G' under ISO 228-1, is a straight cylindrical pipe thread with a 55° Whitworth rounded crest and root profile. Unlike tapered threads, BSPP threads do not seal along the thread flanks, requiring an external bonded elastomeric washer (Dowty seal), O-ring, or copper crush washer on a flat mating shoulder.
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
9 Parameters| Parameter / Spec | ||
|---|---|---|
|
Standard Governing Body
|
ISO 228-1 / BS 2779 / DIN ISO 228 | ANSI / ASME B1.20.1 |
|
Thread Form & Flank Angle
|
55° Whitworth with radiused crests and roots | 60° symmetric truncated V-thread |
|
Common Pitches (TPI)
|
G 1/8": 28 TPI | G 1/4"-3/8": 19 TPI | G 1/2"-3/4": 14 TPI | G 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
|
Bonded seal (Dowty washer), O-ring, or elastomeric gasket on shoulder | Thread flank interference fit + PTFE tape / anaerobic sealant |
|
Primary Geographical Region
|
Europe, UK, Australia, Asia, and global industrial hydraulics | United States, Canada, and Mexico |
|
Thread Designation
|
G (e.g., G 1/2", G 3/4") | — |
|
Taper
|
None (0° — straight cylindrical thread) | — |
|
Taper Ratio
|
— | 1:16 (0.75 in/ft or 1° 47' with centerline) |
|
Max Working Pressure @ 23°C (73°F)
|
— | Up to 5,000–10,000 PSI (dependent on pipe schedule/fitting) |