How to Remove Air Compressor Moisture


According to The Concrete Producer/Concrete Journal Magazine, "a 25-horsepower compressor delivering 100 cfm at 100 psi can produce 18 gallons of water per day at fairly standard conditions of 90-degrees Fahrenheit and 50-percent relative humidity." In applications where even a small amount of water can damage an air tool or a sprayed finish, this amount of moisture is significant. Removing this moisture before it reaches your tools or finish requires regular attention.

Things You'll Need

  • Air compressor
  • Pliers
  • Safety glasses
  • Hearing protection
  • Locate your compressor's drain valve. It is usually installed on or near the bottom of the pressure tank.

  • Put on your safety glasses and hearing protection. Air and water will be forced through the valve by the pressure inside the tank. The sound of air escaping can be extremely loud and a partially plugged valve can send the water in the tank spraying in unexpected directions.

  • Slowly turn the valve counterclockwise to open. If the valve is too tight to turn by hand, apply light pressure with a pair of pliers. Water and air will be forced out of the valve by the air pressure inside the tank.

  • Close the valve by turning it clockwise when the air escaping through the valve is dry. Do not over-tighten the valve. Air should stop escaping through the valve when it is hand-tight.

Tips & Warnings

  • Drain your pressure tank at the end of each day. During periods of high humidity and/or prolonged use, more frequent draining will be required.
  • Standard in-line compressed air filters remove only excess oil from air lines. Desiccant filters and refrigerated moisture extractors, while expensive, are available to remove excess water for critical applications.
  • Water and air will escape from the drain valve under high pressure when the valve is opened. Do not stand or sit in front of the drain valve.
  • Wear appropriate protective gear when working on or operating any power tools.

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  • Photo Credit tools image by Stelios Filippou from
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