Air compressor tank filling with water

Symptoms

• Water sputters out when draining the tank
• Rust-colored water from the drain valve
• Moisture in air lines or at the tool
• Tank feels heavier than expected

Likely causes

• CommonNormal condensation from compressing humid airThis happens in every compressor and is expected, especially in humid climates.
• CommonInfrequent tank drainingWater accumulates and starts rusting the tank interior if not drained after each use.
• PossibleNo inline air/moisture filter on the outputWithout one, moisture travels further into hoses and tools.
• Less commonHigh ambient humidityHumid environments produce more condensation per use than dry ones.

What to do

1. Always drain the tank through the petcock valve after each use while there's still a little pressure to push the water out (a few PSI is enough, no need for full pressure).
2. Tilt the compressor slightly if possible so the drain is at the lowest point and gets all the water out.
3. If the drained water is rust-colored, the tank interior may already have some corrosion; keep draining regularly to slow it further.
4. Add an inline water/moisture filter or separator to the output line if you use air tools that are sensitive to moisture, like spray guns.
5. In humid climates, consider draining mid-use during long jobs, not just at the end.
6. Store the compressor in a dry area when possible to reduce how much moisture it draws in.
7. If the tank ever shows a rust hole or bulge from years of trapped moisture, stop using it and replace the compressor rather than patch the tank.

Tools and parts

• None required; inline filter optional

When to call a pro

If the tank shows rust bubbling through the metal or a bulge, replace the tank or compressor rather than attempting a repair.

Safety