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.

Drain your compressor's tank regularly to reduce the moisture reaching your tools.
  1. Locate your compressor's drain valve. It is usually installed on or near the bottom of the pressure tank.

  2. 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.

  3. 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.

  4. 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.


  • 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.

About the Author

Finn McCuhil is a freelance writer based in Northern Michigan. He worked as a reporter and columnist in South Florida before becoming fascinated with computers. After studying programming at University of South Florida, he spent more than 20 years heading up IT departments at three tier-one automotive suppliers. He now builds wooden boats in the north woods.