naturally carbing a 1/2bbl. need help.

I have searched and come up empty or lost in all of the corny keg threads... I am looking for a decent answer as to how much priming sugar to use to naturally carb a 1/2bbl.

I have found some calculators and they seem to want me to use 13oz-ish. However I have read it takes MUCH less to carb in a keg because of volume.

If this matters it will be a Hoff Stevens keg. I would like to add the sugar and end up with 15 gallons. I estimate that I will have just over 14 gallons before I add the sugar (This is an estimate). The OG was 1.060 WLP kolsh yeast.

My questions:
How much priming sugar (Dextrose/corn sugar) do I need?

Is there a calculator that is useful for kegs? or is there some equation I seem to be not finding?

Has anyone else done this with success?



Thanks in advance.

I've always used the full amount calculated. Never had it over carbonated. You say you have 14 gal and want 15. You are going to add one gallon of priming solution? If so, that sounds like a bit of dilution.

tektonjp said:

I've always used the full amount calculated. Never had it over carbonated. You say you have 14 gal and want 15. You are going to add one gallon of priming solution? If so, that sounds like a bit of dilution.

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My concern is the great the total volume you are carbing in a keg the less you use. I have no idea if the calcs account for this which is why I was looking for some advice.

As for dilution. I planned my IBUs and ABV to end at 15 gallons total volume so it is a bit stronger now in the fermenter.

Zamial said:

My concern is the great the total volume you are carbing in a keg the less you use.

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Sorry, but I have no idea what that sentence means.

My simple science brain tells me that co2 volume should be a constant, that is, regardless of size/amount of wort. If it takes 7 grams of sugar per liter to produce 2.5 V/co2, for example, then a .5 liter bottle takes 3.5, and 20 liters will take 140.

After a few calls + intense digging on the internet I think I have this figured out and I can explain.

The more head space in a vessel the less priming sugar you need due to head space and surface contact area. Inside a bottle you have a small space for the head space and a smaller area of surface contact with the head space. In a corny keg the volume of head space increases as well as the surface contact area. This is why less sugars are needed to carb a keg.

If I take that info into consideration, in a 1/2 bbl my head space will be greater than a corny keg and the surface contact area will be even greater than a corny or bottle. This logic tells me I will require less total sugar than what I would use in a bottle or corny keg.

I think the equation should look like: Volume of wort to be carbed + required priming sugar for desired volumes of CO2 = X. Head space volume + surface contact area with head space = Y. Z = desired CO2 levels. OR X-Y=Z (I left temps out of this equation for simplicity but that can not be overlooked either.)

At this point I will plan to "aim low" and force carb after the fact if I require more carbonation because adding more is easier than trying to uncarb an over carbed liquid.

Its pretty easy. Use half the sugar for naturally carbing in a keg that you would for bottling, given that the volume is the same, say 5 gallons. If its going in a half barrel, that's 15.5gal, so that's 3 times as much (let's just say 15), multiply the sugar you need for kegging your 5gal batch. Or cut the amount of sugar you need for bottling 15 gallons in half. I have never had an issue by doing this. This is what beersmith does. As for you being a gallon short, I would think you would be fine with adding the amount of sugar you need for 15gal to make up for the extra headspace. You will have more sugar by volume so it should create the amount of co2 pressure needed. So at 65*F for 15gal of beer at 2.4 volumes co2, you would need 6oz. Like I said I've naturally carbed in cornies and half barrels multiple times with no issues. Good luck!

Here's the answer: Apply the high calculated amount of sugar, buy a pressure gauge and purge the keg to 30 or 35 psi once per day.

badbrew said:

Here's the answer: Apply the high calculated amount of sugar, buy a pressure gauge and purge the keg to 30 or 35 psi once per day.

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An answer so simple I missed it! I already do closed pressure fermentation so I have a spunding valve w/ gauge already. Now, I just need to engineer it to the Hoff-Stevens barrel. Funny how the simplest solution can be the hardest to find.

Adding 6-6.5oz of sugar (depending on temp) and leaving it alone for a few weeks seems easier to me. That 13oz number is for bottling 15gal.

ODaniel said:

Adding 6-6.5oz of sugar (depending on temp) and leaving it alone for a few weeks seems easier to me. That 13oz number is for bottling 15gal.

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Ok thanks! I do appreciate your insights and missed your post. (Long night last night, wife is on the couch hating life now...) I think I will give your suggestion a try and see what I get. I can always hook the spunding valve up to keep an eye on it.

Thanks for the help!

Hah thought you might have. No problem. I was nervous the first time I tried it, being it's 15 gallons of beer, and I didn't check on it until it was time to tap at a party, hah. Luckily it was perfect.

I’m just starting in the same situation. I’m going from Cornelius 5 gallon soda kegs to Sanke 1/2bbl kegs. I learned that multiplying is not the answer. More is not always better when naturally carbonating. Every recipe is going to require a specific amount of corn sugar, some more or less. Start off with 6oz for 15 gallons. I think these kegs are actually 15.68 gallons or so. These commercial kegs do not have a pressure relief valve on them. But they sure can handle a punch. Over-carbonated brew will lead to over-foaming.

One way is to xfer the brew right into the Sanke is from Cornelius kegs after natural carbonation. Use a special tap and a supply of CO2.

The rubber stopper inside the valve can be removed to cause a “reverse flow” of the fluid. Works well when pressure cleaning/sanitizing the big keg.