# Tank fill valve ID



## pbailey (Oct 19, 2015)

I just bought a 30 gal Kobalt compressor tank with no motor. i want to add it to my existing 15 gal compressor. The one way fill valve is metric and i cannot fit any of my air fittings to it. how can i overcome this? What is that valve called?


----------



## Osviur (Sep 7, 2015)

*Air valve*

Hi,

If this tank is a vertical one, it seems to be part of a VT 6389 Kobalt 2 HP compressor. This tank has an air connection for the discharge check valve.

This one way valve is used to allow the compressor pump to move the compresed air into the tank and when the motor stops, avoid its return toward the compressor. The air contained inside the connecting tube, is released via the pressure control unit (presostat) when it shuts off the motor. This process is done to facilitate the motor start without the resistance presented by the compresed air. The check valve has an auxiliary connection toward the presostat. When this system fails, the motor requires a very high current to overcome this resistance and blows fuses, or trips the protective circuit breaker.

In your case this valve is not necessary if you connect tank to tank, because the original has its own valve.

The threads found in this valve are different, one is a 1/2" NPSM (National Pipe Standard Free-fitting Straight Mechanical Thead), a parallel one, used to receive and compress the discharge tube, and the other side of the valve is a 1/2" NPT (National Pipe Thread)or MPT (Male Pipe Thread) a taper or conical one (3/4" per feet), used to attach the valve to the tank. So if you take out the valve, will find a 1/2" NPT female thread in the tank ready to connect it to the original tank.

To see the valve: CV220301AJ Campbell Hausfeld Check Valve w Fitting Air Compressor Parts | eBay

I hope this help.

Regards


----------



## pbailey (Oct 19, 2015)

Thank you very much. this helps me understand


----------

