Does anyone happen to know how many cubic feet of CO2 is in one of those little 16g CO2 cartridges?

16 grams.  1 mole of CO2 is 44 grams. 16/44 moles.   Any gas, ideal, is 22.1 liters.

PV = nRT

About 8 liters.  About 0.28 cubid feet.

8 liters is only a little over 1/4 of a cubic foot?

0.28546255506607929515418502202643 cu-ft

Yep. One inch is 2.54 cm.  One cubic foot is 1728 cubic inches.  A liter is 1000 ccs

I guess quite a few of those are going to be required to displace 5 gallons of liquid.

Can you use dry ice?

I don't think it would work for the application that I'm thinking of. I may try to use something like a tank off of a paint ball gun.

That should work well enough.  CO2 tanks are up to 24 oz in paintball.

5 gallons?  Are you trying to dispense beer with a portable system?

Here's the problems, in no particular order:

1) A single 12g or 16g cylinder is not enough gas to dispense the whole thing.  The 1/4cuft only applies to standard temp. and pressure.  Beer is stored in the keg at around 10-15 psi and 35-45*F, depending upon style.  You'll get even less volume out of a cylinder under those conditions than calculated.

2) Those cylinders generally contain air tool oil.  It's left over from the manufacturing process and is actually beneficial to paintball guns, air pistols and tools that they may be used in.  For food or beverage uses it puts a sheen on your beer, destroys head retention and tastes kinda funky.

3) You need to regulate the pressure anyhow unless you just really like foamy beer.


You're looking for a product like this:
http://www.midwestsupplies.com/products/ProdByID.aspx?ProdID=7980
But without paying $135, right?

Trust me here, it has to cost that much.  The regulator is the expensive component.

You can grab a 3.5oz or (if you can find them) 7oz. cylinder for paintball use.  Larger than that and they need periodic hydro every 5 years which means that it's really only good for that long before you should just buy another one.  That's $25 for the tank.  The regulator is going to be at least $50 plus some fittings and an air source adapter (pin valve depressor) will run you another $10-20.  You need a keg coupler, too.  For Cornies, $5.  For Sankey, that's $30+.  If you get everything right the first time, you're looking at around $100 for the setup and it will not be as small and convenient as you think it will be.


If you really find the need for this product (i.e. don't feel like just disconnecting your tank and reg and taking it with you), you're better off just buying the commercial one.


One last tip - if you do get a paintball tank, feel free to get it filled anywhere.  Paintball stores just buy their bulk CO2 for local gas distributors, which serve mostly soda machines.  It's all food-grade stuff.

The tank itself, however, should be Cr-Mo.  Do not get a steel tank (they're old, but you can still find them - notably Brass Eagle brand 4oz. tanks)  Catalina makes a 3.5oz Cr-Mo tank that you can buy most places for about $25.  I recommend wevopaintball.com and tell him SCP sent you.

......pumping the keg is a pain in the ass

Watch out for the triple point of CO2.
The ideal gas law breaks down.

You can rent/buy a 50lb cylinder from a welding supply store.

Sure it way too much for one use, but thats a good thing.

Triple (critical) point of CO2 is at about 1150psi at most common temperatures.  You'll never develop that inside a keg with a blowoff set at 125psi (depending upon what make of keg you have).

Also:  DO NOT PUMP KEGS!!!

As soon as you pump one shot of air (with all the bacteria that's in the air) into your keg, you start the clock.  Once that clock reaches 12 hours, your beer will start to taste stale.  At 24 hours, it'll be "skunky" (actually, it's oxidation and not UV damage so it's properly called spoilage and not skunking).  At 36 hours later, you won't even want to drink it anymore.  At the end of the weekend...  watch out!

Keg pumps are an acceptable way to dispense if you can be certain that you will drink all of the beer within 8-12 hours.  If not, don't pump it.



Here are the options you'll want to look into:

1) Build a simple counterpressure filler (about $15) and fill 1/2 gallon growlers ($3-4 each) out of your keg at home.  Take the growlers to the party, enjoy.  Refill and reuse as needed.

2) Make 6-gallon batches and bottle what doesn't fit in the keg for your on-the-go needs.

3) Use 2-liter soda bottles as minikegs.  Drill a hole in the cap and fit a stainless screw-in schrader valve (looks and works like a tire stem) in it.  Fill with beer, cap, then use an air chuck on your CO2 tank to pressurize the bottle through the schrader valve.  You can force-carb through the valve or fill with carbed beer out of your keg and just use the valve to press it up.  Cost for a schrader valve and air chuck should be about $10.  Buy as many as you need and just open them one at a time.

4) If you absolutely must take a full 5 gallon keg with you and you don't want to lug your big tank around or spend the money to buy a portable gas system...  you can cheat by leaving a bit more headspace in the keg (say filling it only 4 gallons) and overpressurizing it right before you leave.  Press the keg up to 30psi and start the clock.  You'll want to remove a gallon of beer within an hour.  After that, the residual pressure in the keg should drop to the 20psi range and allow you to dispense the rest of the beer without danger of overcarbing.  If you wait more than an hour to tap it, though, you'll be force-carbing it and you'll get foaming.  Just use 5 feet of 3/16ID tubing (aka, low-foam tubing) and a party tap lever.  No gas system connected.  This won't work on a sankey (commercial) keg unless you plug the gas port on the coupler.  This method isn't ideal but it's better than pumping air into your beer.


Good luck.

Beer is dispensed at LOW PRESSURES.  And rather low temps but it is accurate enough to estimate CO2 needs for 5 gallons of beer.

One gallon is 231 cubic inches.  With carbonation, it takes about  a pound of CO2.

If you cask condition, it takes far less.  And if you are REALLY CHEAP and have spare kegs, you can keep one as your "generator", keeping a bit of yeast in the bottom and adding boiled malt extract to cause another fermentation.

Use a regulator to control this pressure.

87!!

Having been heavily involved in painball marker repair and customization, I'll add that you might want to degrease the tank's seals and relube them with a food grade lubricant.