How To Remove Water From Air Compressor

How Does Moisture Get into My Air Compressor?

By nature, all air contains some amount of water vapor. Humid climates will result in more moisture while dryer climates will produce less, however some moisture is inevitable. As your air compressor draws in air and compresses it to high pressures, the water vapor condenses and produces droplets as the heated air cools in the tank. Depending on use and atmospheric conditions, a surprising amount of water can end up in your compressor’s air storage tank.

While it is impossible to prevent water from entering your compressed air system. There are easy methods to remove the undesired moisture from the tank and compressed air stream.

How Often Should I Drain My Air Compressor Tank?

You should preferably drain your tank after each use, especially if it is not used regularly. In dryer climates or if experience has indicated that little moisture accumulates you can stretch out the draining frequency accordingly.

How Do I Drain My Air Compressor?

• Make sure the power is off, turn off the power switch, or preferably disconnect the plug or turn off the main power to stationary (hardwired) units.
• For safety, put on a pair of safety glasses or goggles. Gloves are also recommended.
• Reduce the air pressure to 10 – 20 PSI or so. You can do this by pulling the ring on the safety valve or connecting a blow gun to your compressor’s air line. Continue to pull the ring or operate the blow gun until the tank pressure drops to the specified range.
• Locate the drain valve. It will likely be on the bottom or lowest portion of the air tank. There are various types of valves, some twist to open, others are quarter turn ball valves or even full turn gate valves.
• Place a container under the valve to catch the water and or debris that will come out of the tank.
• Slowly open the drain valve to the full open position and let any remaining air and moisture fully drain from the air storage tank.
• Close the drain valve.
• You’re done. Good Job.

For air compressors with hard to reach drain valves, you can add an extension kit to make draining the tank easier.

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Air Drain Extension Kit

If you have a considerable amount of water every time you drain the tank you might want to consider an automatic drain valve. This device replaces your manual drain and periodically automatically drains the moisture from your tank.

Automatic Air Drain Valve

How Do I Remove Water from Air Lines?

You need an air dryer. Commercial units use a refrigerated drying system which can run from several hundred dollars to thousands depending on the size and quality of the system. For the home shop or small to medium sized garage you can likely use a less expensive desiccant, absorption, or membrane air drying system. Both types of air-drying systems can be purchased here.

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How Does an Air Dryer Work?

Air dryers use various methods to remove or separate the water vapor (moisture) from the compressed air system. Refrigerated dryers cool the heated compressed air causing the moisture to condense so that it can be separated and removed from the pressurized air supply.

Coalescing driers force the compressed air through a porous water separation element. The water vapor wets and sticks to the element, where it drips into a reservoir container which contains a manual or automatic water draining valve. These dryers are often combined with air filters and regulators with air pressure gauges to create an Air Drying System as shown.

Air Drying System

Desiccant dryers contain a porous media that readily absorbs water. The water vapor is absorbed into the media until it becomes saturated, then the media must be replaced. Desiccant dryers are typically used as the mid or final stage of a multi-stage air drying system.

More information can be found in this Wikipedia article Compressed air dryer.

The Bottom Line

The bottom line is you don't want water in your air tank or lines period. Keeping water out of your air compressor and compressed air supply lines will make your equipment safer, more efficient and longer lasting. Be sure to check out our popular review categories below.

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