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Problems With Compression Fittings

Question: I do not seem to have any luck when I use any type of compression fitting. They always leak. Am I doing something wrong?

Answer: As you really didn’t say how you are using the compression fittings, I really cannot tell you if you are doing something wrong.

There are however, some basic instructions for the use of compression fittings.

All compression fittings are made up of three parts, as shown in Figure 1.

compression fitting parts

Figure 1 - Compression fitting parts
  1. The body of the fitting.
  2. Ferrule (copper)
  3. Nut

The pipe that is being connected to the compression fitting has the ferrule placed over it and the nut is tightened compressing the ferrule between the pipe and the body of the fitting, hopefully making a leak proof connection for water or gas.

Because the ferrule must compress around the pipe, it is important that the pipe be clean and that there are no scratch marks on the pipe. Having a dirty pipe and/or scratches is the most common failure for compression fittings.

When tightening the nut it is also important that the body of the fitting be held in position so that it does not turn as the nut is being tightened. Many compression fittings have a hex fitting cast into the body to make it easy to put a wrench on the body and hold it in position when tightening the nut.

Another common mistake is to reuse old ferrules. Ferrules cannot be reused once they have been compressed.

It is also important that you use the correct type of compression fitting for the pipe material that you are attempting to join.

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