The process of compressing air generates free water, and increases air borne water vapor.
If you are not sure about why this occurs, take a look at the article entitled “Why does water run out my compressed air line?”.
So what is the problem with a little – or perhaps a lot – of water coming down the compressed air line along with the compressed air?
A simple answer may be that it depends on what you are using the compressed air for.
The more complex answer follows.
For most applications, water blowing out the end of the air line with the compressed air is a problem.
If you are an air-brush painter, a micro-globule of water will land on your artwork, and prevent the paint from adhering to the surface.
You end up with a fish-eye, or a lot of them, depending on how much water your compressor is generating.
Further, compressing air generates higher than normal water vapor content in the compressed air.
When this air reaches a cool surface, the water vapor condenses into free water, making even more fish-eyes.
Air brush painters really have to get all the moisture out of their compressed air, both free flowing water and water vapor.
A lot of us do-it-yourselfers use compressed air to run air tools in our garages.
The water in your compressed air will certainly coat the inside of the tool, and in time, rust it out.
The life expectancy of the tool will be dramatically reduced when there is an air/water mixture running through the air tool.
Water will mix with your lubricating oil that you should be sending, with the air, through the tool.
The water makes a sludge mix with the oil and any airborne debris (dust etc.) that comes with the compressed air.
Then, when this sludge dries out between tool uses, the result might actually prevent the tool from working at all the next time you go to use it.