Don’t use Tank Caps on Systems

This is a video tech tip from our friend Brad at HVAC in SC.

In this video, Brad demonstrates that using a cap off of a refrigerant tank on a system can depress the Schrader core on the system in some cases. Make sure to use proper caps that have seals or brass flare cones.


If you're ever on a service call and you need to use a replacement valve cap, do not use the ones that are on the refrigerant tanks. Here's a perfect example:

The one on the right is just a standard plastic cap. You can see the circle o-ring in there. The one on the left, you can sort of see the dimple in the center. It's just got a flat piece of rubber across the bottom of the valve cap. So, what actually happens is where you see that depression is what's pushing against the valve core. As you can see, this is all oily, and what's happening is when they screw this on, it depresses the valve cap and slowly leaks, as you can probably hear. So, that's how this system lost its refrigerant charge. So, just make sure you're using the proper caps make sure they have o-rings inside of them.

—Brad Hicks


Clinton Klein
Clinton Klein
7/27/17 at 09:09 PM

Awesome tip! Us newer guys and I’m sure some older learned something today.

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