Bspp

BSPP stands for British Standard Pipe Parallel, a standard for pipe threads used to connect pipes and fittings in hydraulic, pneumatic, and plumbing systems. The defining feature of BSPP is that the threads are straight (non-tapered). Because the threads do not provide a seal, BSPP joints rely on a gasket, an O-ring, or a flange-face seal between male and female fittings. In contrast, British Standard Pipe Tapered (BSPT) uses tapered threads that seal by interference.

BSPP threads use a 55-degree thread form and follow ISO 7-1 (with historical roots in BS standards). Sizes are expressed as nominal pipe sizes, typically from 1/16 inch up to 4 inches in common use, though larger sizes appear in industrial applications. The seal is achieved through an external or internal sealing element, not by the threads themselves. Some BSPP fittings are designed as O-ring boss (ORB) variants, where the seal is accomplished with an O-ring.

Although BSPP and BSPT share nominal sizes, they are not interchangeable and require proper matching of thread type. Compatibility with NPT (American standard) is limited due to differences in thread pitch, angle, and sealing method, so adapters are often needed when joining systems that use different standards.

BSPP remains widely used in the United Kingdom and many Commonwealth countries, as well as in various European and industrial applications involving hydraulics, pneumatics, and instrumentation. Its use coexists with other standards worldwide, with ISO 7-1 providing the basis for cross-border compatibility and guidance on proper sealing methods.