A dry air compressor?

dry air compressor
(Last Updated On: August 3, 2020)

I heard some folks were looking for the driest air compressor. Sorry all…no such thing.

Every compressor using free air will generate water. It’s the nature of the beast.

Free air (the stuff we breathe) has water in it, in a vapor form. Some days it’s got lots of water, other days less, but it almost always has water. Some days it seems like it’s 100% water…remember hot, humid summer?

Take about eight cubic feet of that free air at 14.7 PSI (one atmosphere) and compress it to one cubic foot in size, to generate normal compressed air pressure (about 120 PSI) . You now have eight times the water vapor in one single cubic foot.

That concentration of water vapor in the compressed air exceeds the capacity of that air to hold water and the extra water vapor that the air can no longer hold condenses into free water. It pools in the bottom of your compressor reservoir (receiver) and it blows out along your air lines to your application.

The amount of water you get depends on how high you pressurize the free air, how much air you compress, and the relative humidity of the free air that you are compressing. You will always get free water  when you compress air.

Hello, I am Bill, the Compressed-Air-Man. I have years of experience in industrial and residential compressed air applications, air compressors and general pneumatics. I created this site to help professionals, students, and DIYers understand and properly implement and maintain compress3ed air systems.


  1. So, given that water in the compressed air is unavoidable, what is the best way to dry it on the way out? Are there in-line desiccant cartridges?


    Hi Steve:

    Removal of water from a compressed air stream is easy. Though, that doesn’t necessarily mean cheap.

    The first decision you need to make is how dry does my compressed air have to be? Answering that question first will then lead you to find the method that both suits your application, and your budget.

    Check out the link to WATER on http://www.about-air-compressors.com for pages of info on compressor water, and methods of treatment.



Please enter your comment!
Please enter your name here