5lb CO2 tank - how long does it last?

[tzaccario]

Any reputable gas place should be dead on. Mine are always within 1/10 of a pound of the rating on the tank. ( I weigh them when I get home)

Same here, I get 1 to 2/10 of the full 5lbs. With a 7.8lb Tare, 5lbs of gas.. came in at 12.6lbs, just 2/10's shy of the 12.8 full weight.. I am ok with that

 

[IslandLizard]

Don't mean to hijack this thread, but were do you get a tank filled for $25? Closes place that I know on is about $100 for 10 LB tank

You surely are shopping at the wrong place...

CO2 seems to have a "street price" of around $1 a pound. The distributor pays much less of course.

When I called around to get my 2 tanks filled/exchanged some prices were astronomical. 2 outfits claimed I needed "medical grade" CO2, and the price was commensurate. My LHBS charges $3.40 a pound, regardless of fill volume. It's actually quite OK for a 2.5# bottle ($9.50), not so for a 20# tank ($68 !).

At the best places in my area a 20# refill or exchange runs $24-28.

 

[scoobyd63]

It only costs me $25 to fill my 50# tank.

 

[N3Bruce]

The chemistry of CO2 works out so that a 5 lb tank turned into gas at 1 atmosphere at 0 degrees C will yield 1150 liters, more of less of CO2. A 5 gallon Corny will take about 20 liters or so to fill, so if you are carbonating to 2.5 Volumes, you will use about 70 liters per keg, if you count dispensing volume. it would be enough gas to dispense 15 kegs or so, if you account for purging the headspace initially. If you use it like me, and pressurize it to a few PSI to run about a quart of Star San as a final rinse through your kegs and lines, that will change the numbers accordingly.

 

[IslandLizard]

The chemistry of CO2 works out [...]

Great example!
However, it's physics, not chemistry.

 

[brewprint]

I pay roughly $25 for a 10lb tank.

I get about 16 kegs on a 10lb which lasts 6 months or so. I force carb them all. I do use some co2 to purge after it's filled and I put some in a tank with the oxiclean soak and fill the beer lines. That's how I clean my beer lines.

Then I fill enough in the keg to rinse the beer lines with hot water.

I can't imagine that I would get another 10 kegs if I didn't rinse beer lines though.

 

[N3Bruce]

Great example!
However, it's physics, not chemistry.

I was taught gas laws in high school Chemistry, and after all Chemistry is applied Physics

 

[IslandLizard]

I was taught gas laws in high school Chemistry, and after all Chemistry is applied Physics

In certain environments you won't be able to get away uttering such statements without severe consequences, extensive discourse being the mildest.

Although there's some overlap, common ground and applications where one borrows from the other, there is a distinct difference between the 2 sciences and areas of study. High school science does not disclose all there is to know.

 

[doug293cz]

In certain environments you won't be able to get away uttering such statements without severe consequences, extensive discourse being the mildest.

Although there's some overlap, common ground and applications where one borrows from the other, there is a distinct difference between the 2 sciences and areas of study. High school science does not disclose all there is to know.

Always love a good pedant.

Brew on

 

[ba-brewer]

I pay roughly $25 for a 10lb tank.

I get about 16 kegs on a 10lb which lasts 6 months or so. I force carb them all. I do use some co2 to purge after it's filled and I put some in a tank with the oxiclean soak and fill the beer lines. That's how I clean my beer lines.

Then I fill enough in the keg to rinse the beer lines with hot water.

I can't imagine that I would get another 10 kegs if I didn't rinse beer lines though.

After seeing your post I double checked my numbers and I probably get 23 kegs, still pretty far from your numbers. If you put oxiclean in a full 5gal keg and push it all at serving pressure you are using 1 kegs worth of serving gas. If you do that every keg that is going to add up. Also I did not actually count the numbers of kegs it was estimated from gallon brewed per year and how long the tank lasted so my number could be off.

 

[IslandLizard]

Don't forget, when dispensing from a keg at 12 psi it takes (14.7 + 12) / 14.7 = 1.8x the dispensed volume in CO2. That's almost 2 kegs worth of gas per keg!

Or, with @N3Bruce 's calcs and example, dispensing a keg at 12 psi takes, 1.8 * 20 liter = 36.3 liter of CO2, not 20.

The same amount of CO2 is needed for purging a keg filled with Starsan to obtain a 100% pre-purge, when purged to 12 psi "serving pressure."

Even simply purging a quart of Starsan out of a 5 gallon keg (filled with air) at 10 psi takes (((14.7 + 10) / 14.7) * 20) - 19 {air} = (1.68 * 20) - 19 {air} = 14.6 liter of CO2.
That's a lot, almost 3/4 of a keg's volume of CO2!

 

[brewprint]

After seeing your post I double checked my numbers and I probably get 23 kegs, still pretty far from your numbers. If you put oxiclean in a full 5gal keg and push it all at serving pressure you are using 1 kegs worth of serving gas. If you do that every keg that is going to add up. Also I did not actually count the numbers of kegs it was estimated from gallon brewed per year and how long the tank lasted so my number could be off.

I just push enough through the lines to fill a glass. Then I do the same with water. I let the oxiclean sit for at least 24 hours in the line.