How compression fittings work

Written by will charpentier
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How compression fittings work
Exploring the Compression Fitting

A Joint for Many Uses

When small diameter metal tubes or thin-walled metal pipes are joined together, they will be soldered or joined by a compression fitting. Soldering light tubing requires a special skill and making a compression fitting requires a wrench. If the segments of piping or tubing are of dissimilar metals--if a segment of copper pipe to be joined to a segment of aluminium pipe, for example--the compression fitting is the optimum choice to make the joint. One of the most familiar uses of the compression fitting is to join water supply lines to connect household plumbing to the ice maker in the refrigerator. Other uses for small gauge, thin-walled piping include fuel lines, water lines and gas lines for heaters.

How compression fittings work
Exploring the Compression Fitting

Staying Well Connected

A compression fitting joins piping together with sleeve and ferrule, sometimes called the "olive." Compression fittings are more bulky than soldered joints, but can be used to join tubing or piping of different metals. In that case, not only is the compression fitting the quickest way to make an effective joint but it may be the only way. One end of the fitting, the receiver, is threaded. The end of the receiver is also slightly enlarged to allow the insertion of the pipe segment to be joined to it. The other end is not threaded and passes through a compression ring, sometimes called the ferrule or the olive (because of its resemblance to a stuffed cocktail olive). Then it goes through a compression nut, which is threaded onto the receiver and tightened to complete the joint. Plumbers and electricians both recommend that, before assembling a compression fitting, steel wool should be used to remove any burrs from the pipe ends and the threads of the receiver should be wrapped with PTFE Teflon pipe sealing tape.

Maintaining Essential Connections

When the nut is tightened onto the receiver, the ferrule flattens along the pipe in the direction of compression. Its slight deformation also crimps the pipe, meaning that the ferrule acts as a washer between the receiver and the nut without leaks, providing a firm seal that prevents the joint from leaking or being pulled apart. If a leak occurs in a compression fitting, it can be repaired by simply tightening the compression nut.

How compression fittings work
The Compression Nut in Action

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