What is a Compression Fitting?

What is a Compression Fitting?

A compression fitting, as the name suggests, is sealed by the compression of an olive, or sleeve, against a pipe; the olive profile fits to the profile of the fitting (male to female) and completes the seal. Fittings are often nickel-plated brass or plain brass.

compression fittings

How do compression fittings work?

The pipe is pushed into the fitting until it bottoms against a stop. It is important to make sure that the pipe is cut square with any burrs removed and to remember to place the nut, then the olive, over the pipe before final assembly. For larger sizes of metal pipes, it is beneficial to lightly oil the pipe, olive and compression nut before tightening the joint. Ensuring the pipe remains firmly in contact with the stop, screw the nut down finger tight, then tighten a further 1 ¼ to 1 ½ full turns with a spanner, using grips to secure the fitting body. Slacken off the assembly and ensure that the groove made by the olive is even. Release the nut, then re-tighten and give an extra quarter turn. 


How do I select a compression fitting?

As with all system designs, piping and fittings should be selected to allow the necessary flow without undue pressure drop; all necessary fitting shapes should be available from the range for a particular application. Other important considerations are: 

  • working pressure – for compression fittings this is most likely limited by the pipe operating pressure
  • working temperature - increasing temperature will reduce the operating pressure of nylon and polyurethane tubing
  • working environment - both possible contaminants and ease of access for construction and maintenance
  • construction and maintenance - any approvals required for the application, for example, use in the Food Industry


Types of compression fitting?

Across the ranges, all standard shapes are available to complete a system design, both metric and imperial: 

  • variety of straight adaptors
  • bulkhead connectors
  • elbow connector and adaptors
  • variety of tee connector/adaptors
  • cross connector
  • banjo connector
  • hose and tailpiece connectors/adaptors
  • nuts, olives and accessories

All work on the mechanical principle of connection outlined above.


Typical applications for compression fittings?

The rugged and durable nature of the fittings makes them suitable for most industrial applications.


Do I need anything else for compression fittings?

The fittings can be supplied with olive, nuts and any appropriate seals. Piping will be required for the connections to be completed. PA11 or 12 and other plasticised or unplasticised piping and other soft plastic piping. Copper annealed and half-hard; double wall brazed steel pipe. For any new system designs additional components, such as air preparation, actuators and valves will also be required.


More information

Browse our range of compression fittings to find out more