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How do the John Guest fittings work?

To make a connection the tube is simply pushed in by hand. The unique patented John Guest collet locking system then holds the tube firmly in place without deforming it or restricting flow. 

1)      Cut the tube square
Cut the tube square. It is essential that the outside diameter be free of score marks and that burrs and sharp edges be removed before inserting into fitting. For soft thin walled tubing we recommend the use of a tube insert.
2)      Insert the tube
Fitting grips before it seals. Ensure the tube is pushed into the tube stop.
3)      Push up the tube stop
Push the tube into the fitting, to the tube stop. The collet (gripper) has stainless steel teeth which hold the tube firmly in position while the O-ring provides a leak proof seal.
4)      Pull to check and make sure the connection is secure
It is a good practice to test the system prior to leaving site and/or before use.


Push in the collet and remove tube.

To disconnect, ensure the system is depressurized before removing tube. Push in collet squarely against face of fitting. With the collet held in this position, the tube can be removed. The fitting can then be re-used.


John Guest Fittings and valves can be used on the following types of tubing. 

Plastic Tubes – polyethylene, nylon, and polyurethane conforming to the tolerance shown below. For soft or thin wall tube we recommend the use of tube inserts.

Braided hose – Use the Tube to Hose Stems when using braided tube or hose. Use of clamps to retain braided tube on barbs is recommended.

Metal tube (soft) – brass, copper, or mild steel conforming to the following tolerances. Hard metal tubes are not recommended with these fittings.

Size (inches)

5-3/2” - 3/16” OD

1/4” -  1/2” OD

Tolerance (inches)

+ 0.001”/ - 0.003”

+ 0.001/ -0.004”


Title: How do the John Guest fittings work?
Description: Instructions on installing John Guest fittings.
Published: 11/29/2007
Last Edited: 9/18/2013
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