BSP vs NPT vs ACME
BSP (British Standard Pipe)
NPT (National Pipe Taper)
BSP is the standard thread in New Zealand.
- The thread is a triangular (V) shape
- The angle of threads is 55 degrees
- The peaks and valleys are rounded
- BSP has more threads per inch
- The BSP thread pitch is different than NPT. So an NPT male will sometimes fit into a BSPT fitting or vice versa but they may not seal.
NPT seals are the most common in the U.S. and Canada.
- The angle of threads is 60 degrees
- The peaks and valleys are flat
- NPT will feel sharper than BSP
- An NPT male will sometimes fit into a BSPT fitting or vice versa but they may not seal.
NPT male adapters have a taper thread that wedges into the female NPT adapter. They seal due to the "out of roundness principle" which means that the male stretches the female fitting until there is so much force that the connection can hold pressure.
ACME
ACME Thread is a Trapezoidal thread form, with screw thread profiles with trapezoidal outlines.
ACME is an American screw thread having a section that is a mean between the V threads and square threads.
Commonly found on water tanks, IBC's and sprinkler adaptors.
