How to Reduce Excessive Moisture from Your Air Compressor and Lines

Equipping your garage with compressed air can be a game changer if you spend a lot of time working in it. The convenience, power, and versatility of pneumatic tools can transform your humble workspace into powerhouse for serious projects. But whether you run a small compressor with a simple hose or have a large-capacity compressor pushing air through hard lines and wall-mounted outlets, you must eventually figure out how manage moisture in your system.

Your compressor pulls ambient air into its chambers, and that air most likely includes a certain amount of water vapor. Pressurizing that air heats it up, often to the point of saturation. That air eventually cools as it’s decompressed, releasing water into the tank, hoses, lines, and other accessories including tools. And that’s where the trouble begins.

There are several potential issues that arise from excessive moisture in the compressed air. These include:

Corrosion – Obviously, when water continuously encounters bare metal, corrosion is bound to form. This can cause air tools to seize or perform poorly but can also build up inside of lines and junctions, restricting airflow and pressure through the system.

Material contamination – If you’re using compressed air to spray primers, paints, or adhesives, moisture in the system can blend with what you’re spraying, potentially ruining your finish with fisheyes and other conflicts. Built-up debris from corrosion (see above) can also contaminate your finish.

Component wear – Water vapor passing through air tools can rinse out vital lubricants, leading to premature wear.

Ice buildup – If you live in a colder climate and your shop or garage is not heated or well insulated, residual water in your compressor or air lines can freeze. And since water expands in volume when it freezes, the risk for damage to seals, junctions, and other less fortified components that may crack or break from this effect.

Managing moisture

Here is how you can get ahead of potential moisture issues as you set up your shop and compressed air system.

Compressor choice – A common source of excessive moisture is using a compressor that’s not large enough for the job being done. An undersized unit will run more frequently, introducing extra heat because the compressor chamber never gets a chance to cool down between cycles.

Another important decision comes down to the type of compressor itself. Traditionally, air compressors have used a reciprocating piston (or multiple pistons) to pump air. A better alternative for high-volume projects is a scroll-type air compressor. These not only generate less heat (and therefore less moisture) but they also run cooler during continuous use. As a bonus, they are so much quieter and smoother that reciprocating compressors, helping justify the significant difference in price.

Air dryers – Installing filters, dryers, and water traps throughout your system will help capture airborne moisture along its path from compressor to outlet. An inline filter installed at the point of connection to the tool will catch any vapor that may have made it past other points.

Piping system – If you have or plan to install a significant length of piping, whether traditional hard pipes or a flexible system such as Rapid Air, you’ll want to factor some line drops in your layout. By running your horizontal section high on your wall, you can add vertical drops to allow water vapor to condense at the low points before continuing through the rest of the system. Multiple drops will each pull successively more moisture from the air supply. Each of these drops must be fitted with drains to eventually remove accumulated water from the system.

Maintenance – Like any other mechanical system, your compressed air setup will require occasional attention. This includes regular draining of your air tank and any dryers or water traps, as well as changing out filters. When it comes to those disposable inline filters, don’t be stingy; change them out every other project or so, or more often if you’re painting.