How to join pipes together using compression fittings

Compression fittings are very useful to the DIY plumber, there is no messing around with a dangerous blowtorch and compression joints are very strong and if used correctly they will stand the test of time. Compression joints can be used on copper pipe, plastic pipe or even chrome plated pipe and can easily be used to join any combination of these pipes together. These fittings comprise of a threaded body, a nut and a olive or compression ring. When the nut is tightened it squeezes the olive around the pipe and forms a watertight seal.


straight compression fitting

Compression fittings can be used on gas pipes, although this should be left to a professional who is CORGI registered. Compression fittings can also be used to join a piece of copper pipe to a piece of plastic pipe as long as a soft (copper) olive is used instead of a brass olive on the plastic side. A pipe insert must also be used. Compression fittings are useful if you are working on a wet pipe as they will give a good seal where as a end feed or solder ring would not work. Here we are using a compression joint on a piece of plastic pipe.

compression nut and olive

Slide the nut onto the pipe and then the olive, note that there is a pipe insert already inserted here and that the olive is copper, which is essential for plastic pipe. (you can use brass olives but they are more difficult to compress)

compression joint

Push the pipe all the way into the fitting and then tighten the nut, this will compress the olive and grip the pipe.

tighten compression joint

Tighten the nut by gripping the body of the fitting with a pair of water pump pliers then tighten the nut using the correct size spanner or an adjustable spanner.


Repeat this process for each pipe that is to be joined, ensuring that the nuts are tight.

Do Not over tighten the nuts as the fitting could be damaged and may leak!

Push fit fittings are often much easier to use and can easily be used by the DIY'er Copper olives or compression rings are preferred to brass ones as they are much easier to compress.

For an idea of the compression fittings available please see here Compression fittings