Gas Pressure Drop

I'm a kegging n00b. Quick question about force carbing. I put my 5lb bottle in the fridge with the keg. I think the pressure has dropped about 200 psi. Is this typical as the gas bottle gets cold or do I have a leak besides what the keg is using?

Yup that's typical. It may drop to just above the red.

That's pretty typical. A cold co2 will read quite a bit less. As an example- I have a 5 pounder out of the kegerator. It reads 700 right now (it's not full). I have an almost full 10 pounder in the kegerator- it reads about 550.

My understanding is that those gauges aren't all that useful- it'll read 550 from now until it's completely empty, then go right to 0.

It boils down to the nature of liquid CO2; It's liquid under certain pressure, and gas beyond that; colder it will stay liquid longer, but either way it's hard to tell. Just keep an eye on it till it's saying it's empty or in the red, then it will go quick (because it is now almost all gas). This is why I have two gas tanks (also because of hours at local place and trouble getting refilled instead of swapped sometimes). Enjoy your draft HB!

OK - Thanks to all of you! I just bought the bottle so I know its full. I was just surprised how much the pressure drops when it goes from 68 to 39F

My 5lb went from 800psi to 600psi, just from 68f to frig temp

Basic physics

pV = nRT

Basically, given the same volume in the tank, if you drop the temperature, the pressure has to drop as well.

Brewsmith said:

Basic physics

pV = nRT

Basically, given the same volume in the tank, if you drop the temperature, the pressure has to drop as well.

Click to expand...

Yup that's what I was thinking. My engineer-brain didn't think about gas laws and calculating the drop. I couldn't fathom the amount of change...