shrinking co2?

Last night I attached a fresh 5lb tank of co2 to a keg of homebrew. The co2 tank was at room temperature, the beer was cold. It's a new keg setup. I tested for leaks with soap/water solution, no leaks. I set the gauge at 12 psi, and put the whole setup, tank included in the beer fridge. 12 hours later, the co2 tank gauge read 550 psi. It started at 800psi. Was the pressure drop due to the co2 being cold? I can't imagine using that much co2 in a 5 gallon batch of beer in 12 hours. Thanks for any help you can provide.

It's just cold

Pressure drop was from the gas being cold. If you chill your tank before refilling, it will old more. With that said I have never had much luck with the high pressure side of the gauge being accurate anyway!

Thanks for the info!

br1dge said:

Pressure drop was from the gas being cold. If you chill your tank before refilling, it will old more. With that said I have never had much luck with the high pressure side of the gauge being accurate anyway!

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A proper fill will be by weight. It's easier to fill when it's cold, but you should be getting 5 pounds (if that's your tank size) either way. If they put more in there while the tank is cold, it could warm up on your drive home and blow the safety valve on the tank. A couple people have had that happen.

The high pressure gauge accurately tells you the pressure in the tank, but until all your liquid CO2 has boiled off, the pressure in the tank is unrelated to the amount of CO2 left. The only way to know is to weigh it.