Air compressor leaking air from the tank

Symptoms

• Hissing sound from the tank area
• Pressure drops overnight even when not in use
• Visible bubbles when soap water is applied
• Rust or moisture around a seam or fitting

Likely causes

• CommonDrain valve (petcock) not sealingThis valve wears out from repeated use and rust and is the most common tank leak point.
• CommonLoose or corroded fitting threaded into the tankGauges, safety valves, and pressure switches all thread into the tank and can loosen or corrode.
• PossibleInternal tank corrosion from trapped moistureCompressors that aren't drained regularly build up rust from condensation, which can eventually pit through the metal.
• Less commonCracked weld seamSerious and not repairable; means the tank should be retired.

What to do

1. Release all pressure and unplug the compressor before inspecting.
2. Look and feel around the drain valve, gauge, safety valve, and pressure switch fittings for rust, wetness, or damage.
3. Repressurize to a safe low pressure and brush soapy water on the drain valve and every tank fitting to find the exact leak point.
4. If the drain valve leaks, replace it; it's an inexpensive threaded part.
5. If a fitting leaks, drain the tank fully, unscrew it, wrap the threads with thread tape, and reinstall snugly.
6. If the leak is from the tank metal itself (a seam, a rust hole, or a bulge), stop using the compressor immediately and do not attempt to weld or patch it.
7. Replace the tank or the whole compressor if the leak is in the metal rather than a fitting.

Tools and parts

• Adjustable wrench
• Thread seal tape
• Spray bottle with soapy water

When to call a pro

If the leak is in the tank metal itself, a compressed-air tank is not field-repairable; replace the tank or the whole compressor rather than risk a rupture.

Safety