Symptoms of a low CO2 tank?

Silly question time,

I've been keeping an eye on my tank since putting it in the keezer, and due to temp, the vol gauge dipped - no biggy. I've been pouring consistantly around 12psi for a month or two, but in the last week or so it's been pouring sllllloooooooooooowwwww, and I've had to up the reg to meet pressure.

Vol gauge is sitting just into the red, pours slow - time for a refill?

Vol gauge just into the red should be plenty of pressure to push. I have one keg that is pouring slow for no good reason right now, other ones pour fine. Probably something in the dip tube I'm hoping it holds out til the keg kicks, then I'll give it a vigilant teardown.

I'm still on my first tank, but I would say yes. If memory serves when you're in the red you have a lot of high pressure gas but little or no liquid left in the tank. Meaning it will drop much faster from 400-300 as compared to 800-700. Get a refill just to make sure you don't run out entirely.

The top of the red zone pressure is way higher than the 12 psi you need to supply to push the liquid out.

Things to think about if the CO2 tank is showing more than 12 PSI on the high side gauge (which means that the reg is still providing 12 PSI):
How high is your tap above the keg? As the liquid level drops it'll take a bit more pressure to push out the liquid.
Your regulators might have slipped a little - some do with time.
A hop or other debris might have shifted to block the liquid out line a little. You might have overcarbed the keg to begin with, and now the keg has dropped in pressure down to that set on the regulator.
You might have frozen the bottom of the keg a bit (depends on your temperature control - some people use fans in their keezers to prevent this).

The high pressure gauge on a CO2 tank is useless for telling you how much CO2 you have left. Almost all the CO2 in a tank is a liquid, until the tank is very close to empty. As long as there is liquid CO2 in the tank, the pressure in the tank will be determined by the tank temperature, and nothing else. This is the physics of gas/liquid equilibria. The only way to know how much CO2 you have left in the tank is to weigh it (you need to also know the empty (tare) weight of the tank.)

Below is a chart that shows the pressure of CO2 vs temperature (valid only while liquid still present in tank.) Data is from http://www.ddbst.com/en/EED/PCP/VAP_C1050.php



By the way, the same applies to propane tanks.

Brew on

Sweet. Thanks for the education, gang.

Beer's still carbed, still pushing, tank does feel light but I don't have a weight to compare it with (it's a steel 5#) so that point is moot. I'll just keep an eye on it, and look into a 10#'er for a spare.

That'll leave me plenty to fool around with cleaning/purging/pushing and if necessary a backup for the 5# in the keezer.

It's not a bad idea to Weigh the tanks before and after you get them filled, so 1) you know they filled it all the way and 2)You will know exactly how much co2 you have on hand. For example, if you had a big party, it would suck to have the beer stop flowing due to lack of CO2.

sumbrewindude said:

Beer's still carbed, still pushing, tank does feel light but I don't have a weight to compare it with (it's a steel 5#) so that point is moot.

Click to expand...

There should be a tare (empty) weight stamped on the tank somewhere. This weight does not include the weight of your regulator, or down stream plumbing.

Brew on