Legacy - Preventing Air Leakage in a VEX Pneumatic System

An important concern when working with a VEX pneumatic system is air leakage. Any air leaks in the system will reduce the overall pressure and the amount of cycles (extend/retract) the pneumatic system will be able to operate.

Preventing Leaks in Reservoir Fittings



The Air Reservoir fittings consist of the Schrader tire pump valve and the Reservoir fitting

The Reservoir fitting’s threads come with teflon already applied to create a leak-free seal.



A single layer of Teflon tape can be wrapped around the threads of the Schrader tire fitting prior to screwing it into the port of the Air Reservoir. This will help make an airtight seal.



The Schrader tire pump fitting and the Reservoir fitting can be screwed firmly into the ports on the ends of the Air Reservoir using a 7/16” wrench.

Preventing Leaks in Cylinder and Valve Fittings



The fittings for pneumatic cylinders include Cylinder fittings and Flow Meters.



These fittings have a washer which will help create an airtight seal.


Using a small pair of pliers, carefully tighten the fittings to approximately ¼ turn past finger-tight.


The pneumatic solenoid valves use valve fittings.


Valve fittings also have washers to create an airtight seal.


These fittings also should be tightened ¼ of a turn past finger tight with a pair of small pliers.

Cutting, Inserting, and Releasing Pneumatic Tubing


The pneumatic tubing used to connect the pneumatic devices can be cut with a pair of sharp utility shears.

To create an airtight seal, be sure to cut straight across the tubing to create a square end. Do not cut the tubing at an angle.

Note: The longer the length of tubing is between the valve and the pneumatic cylinder, the more air pressure will be lost each time the cylinder is activated.



All of the pneumatic tubing fittings accept the tubing by simply inserting the tubing into the fitting until it comes to a stop.

Be sure the pneumatic tubing is fully inserted into the fitting. There is a rubber ring seal the tubing must pass through to create the airtight seal.

To release the tubing the outer collar of the fitting needs to be pushed in towards the fitting and then the tubing can be removed.

Testing For Leaks


If your pneumatic system is not holding air pressure for a period of time, there is an air leak somewhere in the system.

One way to check for an air leak is to apply a small amount of soap and water solution to the areas where the fittings are connected. If bubbles appear at one of these locations, there is an air leak present and the fitting will need to be tightened.

Note: Do not apply soap and water solution to electronic connections.

For more information, help, and tips, check out the many resources at VEX Professional Development Plus

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