Author Topic: CO2 water vs beer  (Read 292 times)

Offline Bevel

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CO2 water vs beer
« on: January 05, 2022, 07:36:47 pm »
Here’s a question I can’t find the answer to:

If sparkling water is carbonated to about 35-40 psi, which is way more than beer, and folks here say a 5# CO2 tank should last 2-4 kegs of beer, would you blow through a 5# CO2 tank carbonating a keg of sparkling water? How many corny kegs of water would a tank carbonate?

I’m new to keg life and am currently typing with two hands and rolling a keg of water on the floor with my foot, so I guess I will find out soon enough but thought I’d ask!


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Offline Bob357

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Re: CO2 water vs beer
« Reply #1 on: January 05, 2022, 08:50:00 pm »
I don't know who said 5# of CO2 will only last for 2 to 4 Corny kegs of beer, but they're either mistaken or using most of the CO2 for something other than carbonating and serving. I use CO2 to push Starsan out of kegs and push beer into kegs and still carbonate and serve 6 or 7 Cornies with 5#.
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Offline reverseapachemaster

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Re: CO2 water vs beer
« Reply #2 on: January 05, 2022, 09:19:55 pm »
I keep carbonated water on tap always and definitely get through way more than two to four five gallon kegs out of a five pound tank. I'm not sure exactly how may I get but by my rough calculation of how often I fill tanks I must be getting seven or eight per five pound CO2 tank. I carb at 30-35 and push at 20-25. I fill kegs around 4.5 gallons because I don't seem to get good carbonation until there's around four gallons left so filling to five gets a gallon of cold barely carbonated water and four good gallons.

That might seem like expensive for water but I really enjoy carbonated water and try to drink 0.75-1 gallon of water per day. If I bought twelve packs of store brand at $2.50 each I'd go through $17.50 per week. That's a couple bucks less than a five pound tank fill around here.
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Offline narvin

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Re: CO2 water vs beer
« Reply #3 on: January 06, 2022, 04:19:51 am »
Here’s a question I can’t find the answer to:

If sparkling water is carbonated to about 35-40 psi, which is way more than beer, and folks here say a 5# CO2 tank should last 2-4 kegs of beer, would you blow through a 5# CO2 tank carbonating a keg of sparkling water? How many corny kegs of water would a tank carbonate?

I’m new to keg life and am currently typing with two hands and rolling a keg of water on the floor with my foot, so I guess I will find out soon enough but thought I’d ask!


Sent from my iPhone using Tapatalk

That's around 5 volumes of CO2 according to my brewing calculator, compare to 2.5 for an average beer.  Beer contains one volume or so already after fermentation, so you might end up using 3x or more to carbonate a keg of water versus carbonating a beer.

A "volume" of CO2 is how much space it would take up at STP compared to the beer volume.   5 volumes for a 5 gallon keg is 25 gallons or 95 liters.  One mole of an ideal gas is 22.4 L at STP, so this is 4.2 moles of CO2 which weights 44 grams per mole. That's about 6.5 ounces of CO2 for carbonation, which you could round up to a half a pound counting headspace.

Offline narvin

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Re: CO2 water vs beer
« Reply #4 on: January 06, 2022, 05:45:16 am »
You're also going to use more gas to dispense at 40psi, since you've essentially filled an empty keg at that pressure by the end. You can use the ideal gas law to determine how much CO2 that would take.

Offline chinaski

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Re: CO2 water vs beer
« Reply #5 on: January 08, 2022, 12:58:54 pm »
You're also going to use more gas to dispense at 40psi, since you've essentially filled an empty keg at that pressure by the end. You can use the ideal gas law to determine how much CO2 that would take.
NOt sure that is true- I dispense my beer at lower pressure than I carbonate them.  If you were going to dispense at 40 psi, you'd need a really long serving line, wouldn't you?

Offline erockrph

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Re: CO2 water vs beer
« Reply #6 on: January 09, 2022, 10:37:06 am »
You're also going to use more gas to dispense at 40psi, since you've essentially filled an empty keg at that pressure by the end. You can use the ideal gas law to determine how much CO2 that would take.
NOt sure that is true- I dispense my beer at lower pressure than I carbonate them.  If you were going to dispense at 40 psi, you'd need a really long serving line, wouldn't you?
Your carbonation in the liquid will eventually come into equilibrium with the pressure in the headspace. That may not be as noticible with beer if the difference is only a few PSI, but you will see carbonated water or soda go flat fairly quick if the pressure in the headspace drops to half of what is in the liquid.
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Offline narvin

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Re: CO2 water vs beer
« Reply #7 on: January 09, 2022, 10:45:47 am »
You're also going to use more gas to dispense at 40psi, since you've essentially filled an empty keg at that pressure by the end. You can use the ideal gas law to determine how much CO2 that would take.
NOt sure that is true- I dispense my beer at lower pressure than I carbonate them.  If you were going to dispense at 40 psi, you'd need a really long serving line, wouldn't you?
Your carbonation in the liquid will eventually come into equilibrium with the pressure in the headspace. That may not be as noticible with beer if the difference is only a few PSI, but you will see carbonated water or soda go flat fairly quick if the pressure in the headspace drops to half of what is in the liquid.

Right, I don't want my carbonated water to go flat so I keep it balanced. The line length doesn't really matter since water won't foam up.  Soda water dispensers fill at a much higher rate than a tap so the higher pressure helps knock out some of the CO2.

Offline reverseapachemaster

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Re: CO2 water vs beer
« Reply #8 on: January 09, 2022, 11:03:38 am »
I usually cut off the CO2 once the water keg is down to its last gallon or so. By then there's enough CO2 in the keg to push the water out and I don't have problems with it going flat. It might pour a little slower but no real loss of carbonation. I'm usually drinking through that in a couple days so YMMV.
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Offline chinaski

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Re: CO2 water vs beer
« Reply #9 on: January 09, 2022, 03:44:10 pm »
You're also going to use more gas to dispense at 40psi, since you've essentially filled an empty keg at that pressure by the end. You can use the ideal gas law to determine how much CO2 that would take.
NOt sure that is true- I dispense my beer at lower pressure than I carbonate them.  If you were going to dispense at 40 psi, you'd need a really long serving line, wouldn't you?
Your carbonation in the liquid will eventually come into equilibrium with the pressure in the headspace. That may not be as noticible with beer if the difference is only a few PSI, but you will see carbonated water or soda go flat fairly quick if the pressure in the headspace drops to half of what is in the liquid.
Got it- good point.