How to drain and clean an air compressor tank safely

Most likely causes

What comes out of the drain tells you how the tank is doing.

How to drain an air compressor tank

These steps follow DeWalt's manual. Your model may differ, so check your own manual.

1. Turn it off and unplug it. Set the switch to OFF.
2. Turn the regulator down. Set the outlet pressure to zero and remove any tool or hose.
3. Lower the tank pressure. DeWalt says to pull the safety valve ring until the tank is down to about 20 psi. California Air Tools says not to use its safety valve this way. It says to use the drain valve or an air tool instead. Follow your maker.
4. Open the drain valve. It's at the bottom of the tank. Point it at a pan. Wear safety glasses, because water and grit can spit out.
5. Let it run until it's clear and the hiss stops. DeWalt notes the water may hold oil and rust that can stain.
6. Close the drain valve.

If the drain is plugged

DeWalt's fix: release all the air pressure first. Then remove the drain valve, clean it and reinstall it.

Tired of draining? Automatic drains

Some compressors come with an automatic drain valve. California Air Tools fits one to its 8010AAD, which also has a manual ball valve. Auto-drain kits also exist for some models. Draining still matters on an aluminum tank. California Air Tools calls its aluminum tank rust free, but it still tells owners to remove the water.

Why can't you wash the inside of a tank?

A compressor tank is a pressure vessel. The only safe care is to keep water out of it.

• It's sealed. Its only openings are the drain, the fittings and the valves. You can't see or scrub the inside.
• You can't tell what's left. Cleaners or vinegar would have to drain out the same small valve. None of the manuals we checked list this.
• You must not open it up. Campbell Hausfeld's manual says: never attempt to repair or modify a tank. Welding, drilling or any other change weakens it and can lead to a rupture or explosion.

Check the safety valve

The safety valve lets air out if the pressure switch fails. If it sticks, the tank can be over-pressurized.

• DeWalt: pull the ring before you start the compressor to make sure the valve moves freely. If it's stuck or doesn't move smoothly, replace it with the same type of valve.
• California Air Tools: don't pull the safety valve to bleed air from the tank. Using it often to bleed air can damage it.

Those two warnings don't clash. A quick pull to test it is one thing. Using it as a drain is another. Do what your manual says.

For workplaces, OSHA's rule for air receivers says safety valves must be tested often and at regular intervals.

Clean the rest of the compressor

Most "clean air compressor" jobs are on the outside:

1. Unplug it and let it cool. Pumps and heads get hot.
2. Wipe down the outside with a damp rag. Don't spray water into the motor or switch.
3. Brush dust off the cooling fins and the motor vents. Keep the air paths open.
4. Check the intake filter. Tap it clean or replace it as your manual says.
5. Change the pump oil on oil-lubricated models at the interval in your manual. Oil-free pumps have none.
6. Spray soapy water on fittings, the drain and the hose couplers. Bubbles mean a leak. Our guide to air fitting types helps you find the right replacement.

Is the tank getting worse? Signs to replace it

Tank damage is not something you can fix. Replace the tank or the compressor if you see:

• Bubbles or hissing from the tank body or a weld seam.
• Rust that has pitted through the paint on the outside, especially near the bottom.
• A dent or bulge in the tank.
• Rusty water that keeps coming even when you drain after every use.

If that didn't work

• The tank still takes forever to fill. Read air compressor won't build pressure.
• The motor runs nonstop. Read air compressor keeps running. A leak or a bad check valve can cause it.
• The drain valve leaks after you close it. Clean the seat, or replace the valve with the same type.

When to call a pro

Call a compressor service shop or the maker if the safety valve is stuck, the pressure switch doesn't stop the motor, or you see any leak in the tank itself. For larger shop tanks, look at the data plate for the rated maximum pressure. OSHA requires air receivers in workplaces to be built to the ASME pressure vessel code.

Can you clean with an air compressor?

Yes, but turn it down. OSHA's rule says compressed air for cleaning must be reduced to less than 30 psi, and only with chip guarding and personal protective equipment. Wear safety glasses, and never blow dust off your skin or clothes.

Sizing a new compressor? Use our air compressor CFM calculator and read what size air compressor. Running nailers? See coil vs stick framing nailer. More shop guides are in the workshop hub, and the steel material page covers rust.

What you'll need

• Your compressor's owner's manual: Drain and valve steps vary by model
• Shallow pan or rag: Drain water can hold oil and rust that stain
• Safety glasses: The drain can spit water and grit under pressure
• Spray bottle of soapy water: For checking leaks
• Replacement drain valve or safety valve: Same type as the original
• Clean rag and soft brush: For the outside, fins and intake filter

Questions people ask

Change log: Nov 6, 2026: Merged the two archive posts on cleaning compressor tanks. Removed unsafe advice: removing the tank, washing it with soap and water, oiling the inside, vinegar soaks and the claim that moisture turns into vinegar. Added draining steps, safety valve checks, the no-repair rule and replacement signs.