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BSP vs NPT threads: Understanding the Differences

BSP vs NPT threads: Understanding the Differences

The location, environment and pressure system can all affect the way a system is sealed. Whether it is a regional difference or an industry preference, the difference between stainless steel BSP and NPT threads is not about which is better, but rather how it is applied to a pressure system.

NPT Threads

National Pipe Taper Thread (NPT) is most commonly used in the United States (where it was created) and Australia to a lesser extent. Apart from location, there are some unique traits to NPT threads. The male adaptors have a taper thread that wedges into the tapered female adapter and seal, due to the flanks of the threads compressing against each other when sufficient torque is applied. Minimal thread sealant is needed for this style of thread as too much can cause leakage.

NPT threads in Australia are generally supplied as high pressure fittings where both male and female threads are tapered. However, there are some lower pressure fittings available in Australia as 150# fittings that are male tapered and female parallel.


BSP Threads

British Standard Pipe Thread (BSP) is, as the name suggests, common in Britain but is also the most commonly used thread in Australia, as well as being popular in China and Japan. The difference in this style of thread to NPT is the angle across the flanks of the thread (55 degrees instead of 60) and the fact that some pipe sizes for BSP thread vary to NPT thread (21/2” & 6”), which means the two cannot be interchanged.

Like the NPT 150# fittings, the BSP 150# fittings are male tapered and female parallel. BSP threads are most commonly used in Australia as lower pressure 150# fittings but are also available as high pressure fittings where the mating halves are both tapered.


You can purchase and find out more about stainless steel BSP fittings and the differences here or shop our full range of stainless steel fittings here.