Coupling

What is a coupling?

A coupling is a short fitting with female threads on both ends that joins two male-threaded pipes or components on the same axis. It is used to extend a pipe run, repair a broken or cut pipe, and create a straight connection between two parts. Simple as it may seem, selecting the correct size and material is important for the leak-tightness and service life of the installation.

Category contents

• Galvanized couplings: For economical and general use.
• Brass couplings: Corrosion-resistant; for drinking water and hot water lines.
• Nickel-plated brass extensions: One end female, the other male thread; used to bring faucet and mixer connections forward from the wall.

Extension fittings are a practical solution for bringing forward connection points that are recessed inside the wall due to tile and plaster thickness.

Choosing the right coupling

The coupling size must match the thread size of the pipe being joined; reducing fittings are used to connect two pipes of different sizes. Selecting a coupling that matches the material of the line reduces the risk of galvanic corrosion. Brass couplings should be preferred in hot water lines.

Installation recommendations

Make sure the threads are clean and undamaged, and wrap PTFE tape in the direction of the thread turn. Thread both pipes into the coupling equally so that the pipes meet in the middle. Overtightening can damage the threads; pressurize the line after installation to check for leaks. When repairing a broken pipe, both pipe ends must have clean threads; different repair fittings should be used for unthreaded ends.

Frequently asked questions

What is the difference between a coupling and a nipple?

A coupling has female threads on both ends and joins male-threaded pipes; a nipple has male threads on both ends and joins female-threaded parts.

What does an extension fitting do?

It brings a recessed connection point in the wall forward, allowing a faucet or mixer to be fitted easily.

Can a galvanized coupling be used in hot water?

It can; however, brass is preferred for longer service life.

Which size should I get?

Check the thread size of the pipes to be joined; 1/2 inch is the most common size in domestic installations.

Where can I find other fittings?

For elbows, tees, and unions, see the fittings and materials category.

How tight should a coupling be?

Starting by hand and then tightening a few turns with a wrench is sufficient for most connections; overtightening can strip the threads.