BSPP Pipe Thread vs. BSPT Pipe Thread
Comparing 2 standards across 8 specifications. 7 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.
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.
Specification Comparison Table
8 Parameters| Parameter / Spec | ||
|---|---|---|
|
Standard Governing Body
|
ISO 228-1 / BS 2779 / DIN ISO 228 | ISO 7-1 / EN 10226-1 / BS 21 / DIN 2999 |
|
Thread Designation
|
G (e.g., G 1/2", G 3/4") | R (Male taper), Rc (Female taper), Rp (Female parallel) |
|
Thread Form & Flank Angle
|
55° Whitworth with radiused crests and roots | 55° Whitworth with radiused crests and roots |
|
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 | R 1/8": 28 TPI | R 1/4"-3/8": 19 TPI | R 1/2"-3/4": 14 TPI | R 1"-2": 11 TPI |
|
Sealing Mechanism
|
Bonded seal (Dowty washer), O-ring, or elastomeric gasket on shoulder | Metal-to-metal flank wedging + jointing paste/PTFE tape |
|
Primary Geographical Region
|
Europe, UK, Australia, Asia, and global industrial hydraulics | Europe, United Kingdom, Japan (JIS B 0203), Commonwealth |
|
Taper
|
None (0° — straight cylindrical thread) | — |
|
Taper Ratio
|
— | 1:16 (0.75 in/ft or 1° 47' with centerline) |