How to Measure BSP Fittings

BSP stands for ‘British Standard Pipe’ threads. BSP is the most popular thread style in the United Kingdom and is very common in the UK commonwealth countries. They are also widely used for many applications in Europe and Asia. BSP male fittings have a conical 30-degree seat that mates against matching conical 30-degree female fitting or port. BSP fittings have a thread angle of 55 degrees and come in two thread types: 

• BSPP — parallel threads, sealed with a bonded washer or O-ring, seated under the shoulder of the male fitting and the face of the female fitting or port. 
• BSPT — tapered threads, sealed by a metal-to-metal wedge of the threads and the application of a thread sealant prior to installation.  

Make sure to avoid the common mistake of confusing a BSP thread of 55 degrees with an American NPT (National Pipe Taper) of a 60-degree angle. BSP have rounded peaks and valleys, while NPT have flattened peaks and valleys. They may seem to fit, but the difference in thread angle and style will allow for leaking down the threads. When in doubt, verify the style with a thread gauge.

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