Coupling (piping)

Pipe coupling (copper sweat)

In piping and plumbing, a coupling (or coupler) is a very short length of pipe or tube, with a socket at one or both ends that allows two pipes or tubes to be joined, welded (steel), brazed or soldered (copper, brass etc.) together.

Alternatively, it is a short length of pipe with two female National pipe threads (NPT) (in North American terms, a coupler is a double female while a nipple is a double male) or two male or female British standard pipe threads.

If the two ends of a coupling are of different standards or joining methods, the coupling is called an adapter.^[1] Examples of adapters include one end BSP threaded with the other NPT threaded, and one end threaded with the other a plain socket for brazing.

A coupling whose ends use the same connection method but are of different sizes is called a reducing coupling or reducer. An example is a 3/4" NPT to 1/2" NPT coupling.^[2]

See also

• Closet flange
• Eccentric reducer
• Nipple (plumbing)
• Piping and plumbing fittings
• Reducer
• Street elbow

References

Further reading

• ASME B1.20.7 Hose Coupling Screw Threads, Inch. (Quote: The normal sequence of connections, in relation to the direction of flow, is from an externally threaded nipple into an internally threaded coupling)

External resources

• PDF illustrating assorted adapters

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