CO2 Tank Longevity

[LeverTime]

How long should a CO2 tank last? My regulator said the pressure in the CO2 tank was just under 800 psi when I first hooked it up, and after kegging and dispensing what I guesstimate to be 1/3rd of my first keg, it's down to just under 600 psi. Do these things really only last about 2 kegs?

 

[libeerty]

If the tank is in the fridge, like mine is, the reading will always be lower than it really is, completely unreliable. Science has something to do with it.

If it is outside the tank, and it really used 1/4th of it already, then there might be a leak.

A 5 lb. tank is good for ~6 or so kegs. That squiggly line before the 6 is because it is dependent on all sorts of things, but definitely more than 2.

 

[LeverTime]

If the tank is in the fridge, like mine is, the reading will always be lower than it really is, completely unreliable. Science has something to do with it.

If it is outside the tank, and it really used 1/4th of it already, then there might be a leak.

A 5 lb. tank is good for ~6 or so kegs. That squiggly line before the 6 is because it is dependent on all sorts of things, but definitely more than 2.

It was originally outside the fridge (~800), then I put it in the fridge before noticing it was at ~600. I bet that's why it dropped.

Thanks.

 

[zachattack]

The reading is always reliable, whether the tank is in the fridge or not. Unfortunately, since CO2 is mostly in liquid form within the tank, the pressure you're reading is the liquid's vapor pressure and it's not related to how much CO2 you have left in the tank. The vapor pressure goes down with temperature, according to the attached chart.

The only way to know how much you have in there is to remove the regulator, weigh the tank, and subtract the tare weight stamped in the tank.

When you run out of liquid CO2, you're literally "running on fumes" and the tank pressure will start to drop very rapidly. At that point, get it refilled.

 

[LeverTime]

The reading is always reliable, whether the tank is in the fridge or not. Unfortunately, since CO2 is mostly in liquid form within the tank, the pressure you're reading is the liquid's vapor pressure and it's not related to how much CO2 you have left in the tank. The vapor pressure goes down with temperature, according to the attached chart.

The only way to know how much you have in there is to remove the regulator, weigh the tank, and subtract the tare weight stamped in the tank.

When you run out of liquid CO2, you're literally "running on fumes" and the tank pressure will start to drop very rapidly. At that point, get it refilled.

This makes sense, thanks.

Just out of curiosity, where did you get that graph?

 

[zachattack]

This makes sense, thanks.

Just out of curiosity, where did you get that graph?

I made it from data available on Wikipedia. I just converted some of the units here and graphed it in Excel.

http://en.wikipedia.org/wiki/Carbon_dioxide_data#Liquid.2Fvapor_equilibrium_thermodynamic_data

 

[Doed]

I don't understand the short longevity some of you have. I have a 5lb tank on the outside of my keezer. I use it to force carb and serve my homebrew plus serve commercial ½ barrels. The tank I currently have is just now about to run out, but it has been on my keezer since May of last year. I guess on the next 5lb tank I am going to have to keep track of how many kegs I get out of a tank but I know that this current tank has served at least 3 - ½barrels and numerous homebrew kegs, probably 6 - 8.

I force carb and serve at 12psi.

Yes, I am positive it is a 5lb tank.

 

[Moose1231]

The reading is always reliable, whether the tank is in the fridge or not. Unfortunately, since CO2 is mostly in liquid form within the tank, the pressure you're reading is the liquid's vapor pressure and it's not related to how much CO2 you have left in the tank. The vapor pressure goes down with temperature, according to the attached chart.

The only way to know how much you have in there is to remove the regulator, weigh the tank, and subtract the tare weight stamped in the tank.

When you run out of liquid CO2, you're literally "running on fumes" and the tank pressure will start to drop very rapidly. At that point, get it refilled.

That's right. If there was only gas in the tank, you could know the mass of the CO2 by using the perfect gas formula. Unfortunatly, since at high pressure and low temperature, the CO2 is liquid, the perfect gas formula won't work. The only pressure that the regulator displays is the vapor pressure which, depends only on the temperature, and hence, that is why the pressure drop in the fridge.

 

[zachattack]

I don't understand the short longevity some of you have. I have a 5lb tank on the outside of my keezer. I use it to force carb and serve my homebrew plus serve commercial ½ barrels. The tank I currently have is just now about to run out, but it has been on my keezer since May of last year. I guess on the next 5lb tank I am going to have to keep track of how many kegs I get out of a tank but I know that this current tank has served at least 3 - ½barrels and numerous homebrew kegs, probably 6 - 8.

I force carb and serve at 12psi.

Yes, I am positive it is a 5lb tank.

I think it depends on how you use it. A lot of people probably purge excessively, a lot of people use CO2 to prime siphons, flush kegs, flush jars of hops, flush carboys, push cleaner/water/sanitizer, a lot of people force carb at higher pressures then vent (wasting CO2) and lower to a serving pressure, etc. In the end, CO2 is a pretty low expense when you look at homebrewing as a whole, but since it's kind of a pain to get filled (even with a good local shop with good hours) I hate to waste it.

 

[slcdawg]

I get a lot of use out of a 5lb CO2 tank before needing to refill. I get at least eight cornies (5 gal) force carbed.

I recently increased production, so I have a keg on standby for a few weeks before being able to hook up to CO2. I started using a sugar solution when transferring to the keg to conserve CO2 even further. But, I easily get 8 or more force carbed kegs (without the sugar).

 

[Doed]

I think it depends on how you use it. A lot of people probably purge excessively, a lot of people use CO2 to prime siphons, flush kegs, flush jars of hops, flush carboys, push cleaner/water/sanitizer, a lot of people force carb at higher pressures then vent (wasting CO2) and lower to a serving pressure, etc. In the end, CO2 is a pretty low expense when you look at homebrewing as a whole, but since it's kind of a pain to get filled (even with a good local shop with good hours) I hate to waste it.

You make some good points and I don't use CO2 to flush kegs/carboys/etc so this is most likely one reason why I get better longevity.

 

[JuanMoore]

You make some good points and I don't use CO2 to flush kegs/carboys/etc so this is most likely one reason why I get better longevity.

That and it takes much less gas to simply push a commercial keg that's already carbonated than it does to both carbonate and serve a keg. General rule of thumb is that one pound of CO2 can carbonate and serve 5-10 gal of beer, depending on carbonation levels and how much you use to purge. For just serving, that same one pound of CO2 is good for 15-20 gal of beer.