Filling a Keg Half Full (CO2 wasted?)

pavyaz19 · 09-09-2009, 10:48 PM

A friend and I brewed a 5 gallon that we'd like to split. We don't want to bottle since we have new kegerators... How much C02 is wasted by filling a 5 gallon keg with only 2.5 gallons of beer?

Is this a huge problem or no big deal?

Thanks!

chuggs · 09-09-2009, 10:56 PM

At 2.5 volumes of CO2... you each waste 1.25 x 5 gal or 6.25 gallons (gaseous) of CO2...but you can't look at it that way. You'd have spent that much CO2 getting down to half a keg anyway. You got to look at it as half full instead of half empty

Enjoy sharing the beer!

the_Roqk · 09-09-2009, 10:58 PM

How big is your Co2 bottle 5.10.20 lb. If even talking abut a 5 lb'er then your pressure drop will be minimal. Not sure about how many "pulls" one can get out of a 5 lb'er, or even a 10 lb'er. I do know that I have a 20 lb'er that I've been using for the past year and it still registers around 950 lbs. But I do know that it will bottom out on you real fast so residual pressure means nothing unless you weigh the cylinder.

pavyaz19 · 09-09-2009, 11:05 PM

I have a 10 lb CO2 cylinder.

One other quick question since I'm so new to kegging. I plan on using priming sugar instead of force-carbing. If I do this, it is not necessary to run any CO2 into the keg whatsoever until I'm ready to drink, correct? In other words, I won't run CO2 to the keg for at least 3 weeks after priming.

Thanks much for the help!

chuggs · 09-09-2009, 11:08 PM

It's a good idea to pressurize the keg to get the hatch o-ring to seal good. Otherwise there's a good chance that the co2 will just leak out...and you'll have flat beer.

pavyaz19 · 09-10-2009, 01:25 AM

Does this mean that I'll be double-carbing the beer? If I have the priming sugar in there already, why would I want even more CO2? I get it's to seal the keg, does this mean I put a very low pressure of CO2? If so, how much?

chuggs · 09-10-2009, 01:30 AM

Well...if your keg is pretty full...and there is little head space...the amount of CO2 that you're putting there is pretty insignificant. I'd put a quick 15 psi on it to make sure you get a seal. Then disconnect the gas. As the liquid absorbs the CO2...the pressure will decline, but hopefully, your secondary fermentation going on will make up for that. And you'll get normal Carbonation. I wouldn't worry about a thing. The beauty about kegging is...if you get it a little too carbonated, or under carbonated...it can be fixed

the_Roqk · 09-10-2009, 02:12 PM

Quote:

Originally Posted by pavyaz19

I have a 10 lb CO2 cylinder.

One other quick question since I'm so new to kegging. I plan on using priming sugar instead of force-carbing. If I do this, it is not necessary to run any CO2 into the keg whatsoever until I'm ready to drink, correct? In other words, I won't run CO2 to the keg for at least 3 weeks after priming.

Thanks much for the help!

You'll need to purge the keg of oxygen by using your CO2. Also by adding around 15 lbs it will seal the keg lid O-ring. Just be aware that when the time comes to partake of your natural carbed beer that you will have more yeast to contend with after a few pulls. Crash cooling after your 3 weeks of natural carbing should take care of it.

**Bobby_M** · 09-10-2009, 03:08 PM

Quote:

Originally Posted by chuggs

At 2.5 volumes of CO2... you each waste 1.25 x 5 gal or 6.25 gallons (gaseous) of CO2...but you can't look at it that way. You'd have spent that much CO2 getting down to half a keg anyway. You got to look at it as half full instead of half empty

Enjoy sharing the beer!

I'm confused. 2.5 volumes at 43F for example, takes 14psi which is 2ATM. In a 5 gallon keg, that's 2x5 gallons or 10 gallons of gaseous CO2. Where am I going wrong? I'm thinking that it's 10 gallons of CO2 whether there's a pint, gallon or 5 gallons in the keg. It has more to do with the size of the container and how much pressure you apply.

chuggs · 09-11-2009, 02:02 PM

You're right 14 psi... 14.696 psid to be exact or ~29.4 psi absolute...would be 2 ATM of pressure...which at Standard Temperature would be 2 Volumes...but if you change the temperature, the volume changes. So you're squeezing in more volumes at the lower temp. If I remember correctly Standard Temp ** is 15.56 degrees Celcius (60 degrees Farenheit) Go into the Carb charts with 60 degrees and 14.696 psi and see what you get. Then look at the same information at 42 degrees or so...

The calc I did before was just figuring the amt of CO2 that would be sitting in the head space above his 2.5 gallons, that otherwise would have been disolved into his buddy's half of the beer. Convuluted Idea, eh?

Anyway...at the lower temp...you'll be getting more volumes absorbed. So if it's a 5 gal keg...and you're putting 2.5 volumes in it...it would be 5 * 2.5 or 12.5 gallons of CO2. (free volume of co2 at 60 degrees f and atmospheric pressure of 14.696 psi (1 ATM)

** Seems the Standard I learned has changed over the years... I'm going back to the 70's...

See this link for more on "Standards"

http://en.wikipedia.org/wiki/Standard_conditions_for_temperature_and_pressure#I nternational_Standard_Atmosphere