National Pipe Taper. The thread tapers 1 in 16 on diameter, so male and female threads wedge together as they are made up, and a sealant such as pipe dope or PTFE tape fills the spiral leak path at the crests and roots. Common on small valves and fittings, it is not interchangeable with BSP threads used in much of the world, even where the thread counts look close.
Fitting's BSP and the valve is NPT, it'll start but it'll never seal, find the right adapter.
Also heard as
- MPT
- FPT
- MNPT
- FNPT
- pipe thread
Related terms
Make up
To screw a threaded joint together and tighten it, or to assemble and torque a flanged joint.
Pipe dope
Paste thread sealant brushed on male pipe threads before makeup to seal and lubricate the joint.
Nipple
A short length of pipe, threaded or plain on its ends, used to connect two fittings or a valve to a fitting.
Socket weld
An end connection where the pipe slides into a recessed socket and is joined by a fillet weld around the outside.