How Many Kegs out a 5lb tank?

I just kegged my first beer tonight and I am wondering how many batches I'll be able to keg before my c02 runs out? Any words of wisdom?

I've asked this question a thousand times....Get the same rubbish answer.
"Well it depends on if you're dispensing or carbonating and dispensing, and the angle of the earth in direct disproportionate triangulation with the spectrum of beer flowing from the cosmic regulator in geosynchronous orbit that follows the lunar patterns of tidal activity in the mountain time zone during daylight standard and how big your starter is." and on and on and on and on.

To date I have had 4 batches carbed on my 5# tank. I've heard on average 8-10 kegs.

8-10, but if you really want to figure it out... figure out what BK said.

Roman Brewer said:

I just kegged my first beer tonight and I am wondering how many batches I'll be able to keg before my c02 runs out? Any words of wisdom?

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There is no real answer. There's too many variables. If you have a tight co2 system (i.e. no leaks) and carbonating and serving on the tank you'll probably be able to push around 10 kegs give or take a couple kegs. They last quite awhile.

I am still on my first 5 lb tank, and have served about 8 kegs. This has been over a year and a half, since I moved in the middle and was unable to brew for awhile. I have just been waiting for it to run out lately, but it keeps going.

I carb with a 20# tank, so the 5# tank in the kegerator will last and last till the Sunday morning of a big BBQ and then give up the ghost. That's why I have a spare 5 pounder ready to go.

Once you go through a few kegs, you'll find that you use a lot in addition to just carbing and pushing. Think about when the keg is just about empty. It's filled with co2 at say 12 psi. When you clean it out for the next batch, it all goes away.

I've tried hard to research it and figure out the exact numbers but it's over my head. Here's where I ended up, but I think someone on HBT eventually explained a flaw or two..

"According to http://www.ca.airliquide.com/en/business/products/carbon_diox/index.asp , 1 pound of CO2 (it's sold by the pound) is equal to 8.741 cubic feat of gaseous CO2 at sea level / 70F. If my logic serves me, this volume would actually be halved at typical carbonation pressure of say 14 psi (2ATM) for 4.37 cuft. I'm going to ignore the temperature.

5 gallons is .668 cubic feet. 4.37cuft (1lb co2) divided by .668 = 6.54. That means 1 pound of liquid CO2 is 6.54 volumes in a 5 gallon keg. For example, that would be enough to carb two kegs to 2.25 volumes and dispense both to empty."

PV=nRT

V=nRT/P

PV/nRT=PV/nRT

PV/T=PV/T

P(tank)*V(tank)/T(tank)=P(keg)* V(keg)/T(tank)

P=pressure
V=volume
T=Temp (absolute)

So....
V(keg)=P(tank)*V(tank)*T(keg) / T(tank)*P(keg)

Special Hops said:

PV=nRT

V=nRT/P

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See.....I told You.

Yeah but it's a Fricken pain... working with Kelvin and all ;-)

This is why I find its MUCH easier to just drink HB until I dont really care about how much CO2 is left, as I have a spare tank. Way to much math for me, I just keep an eye on the high pressure gauge.

Displaced MassHole said:

This is why I find its MUCH easier to just drink HB until I dont really care about how much CO2 is left, as I have a spare tank. Way to much math for me, I just keep an eye on the high pressure gauge.

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+1 :rockin:

Assuming a 5 lbs CO tank is ~1/2 gal in volume and filled to 800 psig

V(keg)=(800 psig)(.5gal)(278K)/(5 psig)(298K)

V(keg)= 74.6 gallons.

So split that into 5 gallon kegs and you get 15 kegs. However, this does not take into account the CO2 absorbed into the beer when you force carb, which is a good bit.

So in other words this sums it about up.

BigKahuna said:

I've asked this question a thousand times....Get the same rubbish answer.
"Well it depends on if you're dispensing or carbonating and dispensing, and the angle of the earth in direct disproportionate triangulation with the spectrum of beer flowing from the cosmic regulator in geosynchronous orbit that follows the lunar patterns of tidal activity in the mountain time zone during daylight standard and how big your starter is." and on and on and on and on.

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Displaced MassHole said:

This is why I find its MUCH easier to just drink HB until I dont really care about how much CO2 is left, as I have a spare tank. Way to much math for me, I just keep an eye on the high pressure gauge.

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With a spare tank, I keep an eye on the faucet. When it stops coming out even though the valve is open, I usually need a new tank.

EdWort said:

With a spare tank, I keep an eye on the faucet. When it stops coming out even though the valve is open, I usually need a new tank.

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or keg, whichever.

camiller said:

or keg, whichever.

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Very true, I'd rather run out of gas than beer, you can always just get a big @ssed straw and stick in in the corny.