BSPP Pipe Thread vs. Faucet Aerator Threads
Comparing 2 standards across 13 specifications. 13 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.
Faucet aerators utilize standardized ultra-fine metric and imperial screw threads to attach flow restrictors and stream straighteners to residential and commercial spouts. Common sizes include Standard M24×1.0 male, 55/64"-27 female, Junior M18.5×1.0, and Tom Thumb M16.5×1.0; bathroom lavatory faucets are commonly EPA WaterSense-certified for reduced flow, though the WaterSense program does not cover kitchen faucets.
Specification Comparison Table
13 Parameters| Parameter / Spec | ||
|---|---|---|
|
Standard Governing Body
|
ISO 228-1 / BS 2779 / DIN ISO 228 | ASME A112.18.1 / CSA B125.1 / NSF 61 |
|
Thread Designation
|
G (e.g., G 1/2", G 3/4") | — |
|
Thread Form & Flank Angle
|
55° Whitworth with radiused crests and roots | — |
|
Taper
|
None (0° — straight cylindrical 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 | — |
|
Sealing Mechanism
|
Bonded seal (Dowty washer), O-ring, or elastomeric gasket on shoulder | — |
|
Primary Geographical Region
|
Europe, UK, Australia, Asia, and global industrial hydraulics | — |
|
Standard / Regular Size (Metric)
|
— | M24 × 1.0 mm (Male) | M22 × 1.0 mm (Female) |
|
Standard / Regular Size (US Imperial)
|
— | 15/16"-27 UNS (Male) | 55/64"-27 UNS (Female) |
|
Junior Size
|
— | M18.5 × 1.0 mm (Male) | 13/16"-27 UNS (Female) |
|
Tom Thumb / Tiny Junior
|
— | M16.5 × 1.0 mm (Male) | 5/8"-27 UNS (Female) |
|
Standard Flow Rate (Bathroom WaterSense / Kitchen Federal Max)
|
— | 1.2–1.5 GPM bathroom lavatory, EPA WaterSense-certified | up to 2.2 GPM kitchen, per the federal EPAct maximum (EPA WaterSense has no kitchen faucet certification program) |
|
Sealing Method
|
— | EPDM rubber flat washer compressed against spout shoulder |