Here is a quick tank check valve checkup.
Most DIY and smaller air compressors have a compressor tank check valve. It is typically located where the air line from the pump head enters the compressor tank.
Why bother doing a tank check valve checkup?
Typically it’s because your air compressor does not hold air. The compressor fills the tank, the compressor stops, and over time – maybe a minute, maybe overnight – the compressor tank empties on it’s own.
If you have left your air compressor plugged in, that means when the tank pressure reaches cut in, the compressor will start. That is not something most of us want happening in the middle of the night from an air compressor that’s in the basement that’s right under the bedroom.
In the photo below, the tank check valve is commonly found where the red dot is. That is, where the line from the pump head enters the compressor tank.
How To Do A Quick Tank Check Valve Checkup
Unplug the air compressor.
Drain all the air from the tank.
Remove the line from the pump where it is attached to the fitting at the tank if it has only one, or both lines if your compressor has a line over to the unloader valve as well.
Put a wrench on the flats of the fitting, and turn (normally counter-clockwise) until the thread seal releases.
Continue turning the fitting – complete with tank check valve – out of the tank.
Wipe it clean.
You will normally see three or four holes on the sides of the check valve near the bottom.
Place your lips over the check valve to seal around the valve – not blocking those holes – and blow… hard!
If air comes out of the hole either where the line from the pump was plumbed, or out of the port for the unloader valve line, you need to clean, rinse, and test your tank check valve again.
If you cannot get the tank check valve to stop air coming up out of the tank after a thorough cleaning, we suspect it will be time to acquire and new one.