IS 554 specifies BSP (British Standard Pipe) threads for pressure-tight joints. It covers taper threads (R) for sealing joints and parallel threads (G) for mechanical joints. This is the thread standard used for all plumbing and pipe fitting connections in India.
Specification for pipe threads (BSP taper and parallel) for making pressure-tight joints, covering thread form, dimensions, tolerances, and gauging.
Key Values
Thread angle55° (Whitworth form)
Taper1:16 on diameter
Threads per inch (1/2")14 TPI
Practical Notes
! India follows BSP (55°) thread standard, NOT NPT (60° US standard). BSP and NPT are NOT interchangeable.
! For pressure joints, use taper thread (R) on the male end. The taper creates the seal as it tightens.
! PTFE tape or thread sealant is still required even on taper threads for reliable sealing.
! When specifying imported fittings, always confirm BSP compatibility — US/Japanese fittings use NPT threads.