fitting diagram

About this Project

Use compression fittings in places where you may need to take the run apart someday or where it is difficult to solder. One common location is on supply lines for a sink, which have compression fittings at both the stop valve and the faucet inlet. Flexible supply lines are an even easier way to make this connection (see Stopping Leaks in Flexible Supply Lines, Related Projects).

Compression fittings usually are used with flexible copper tubing, but may also be used with type-M rigid copper (Choosing Pipe, Related Projects). These fittings are not as strong as soldered joints, so they should not be hidden inside walls.

The compression nut forms a seal by squeezing the ferrule against the copper pipe. Because copper is a soft metal, the seal can be extremely tight. Still, use pipe joint compound to make sure the seal is watertight. Anchor or support the tubing within 2 feet of either side of the fitting.