I have a 5 gallon keg that I have filled with approximately 4 gallons of liquid. The keg has an inlet and outlet fitting for gas carbonation. The inlet fitting is shallow and the outlet fitting goes all the way to the bottom of the tank.

My normal carbonation process is done through a pump connected to the keg moving the liquid around and this pump is also connected to the gas cylinder pumping 10psi of CO2. The keg with the liquid is equilibrated after ~3 hours. The pump sucks up the liquid from the outlet fitting going through 10psi of CO2 and is pumped back through the inlet.

I want to know how long this process ought to take if I do not run the liquid through a pump with CO2 and straight out connect the CO2 to the outlet fitting to carbonate from the bottom up. I can also do it through the inlet fitting but I think carbonating from bottom up might be faster.

If i do it this way I'd need to be rolling the keg once in a while during the carbonation to equilibrate. If I had a pressure gauge I could connect it to the outlet fitting and see where the internal psi stands after some time. Unfortunately, I do not have one.

2 Answers 2


I use corny kegs (picture below), to fully carbonate I pump to 30psi and leave for a week, re-pump (open the bottle valve) to 30psi every so often when the pressure drops through absorption or leave the bottle attached and valve open.

Or (I don't really like doing this) lay keg on its side with the gas connector up, then pressurise to 30psi leave the bottle attached and valve open then rock the keg back and forth. This way gives you a greater surface area of the liquid to absorb the CO2 quicker and takes 20 minutes or so, but taste it every so often and stop when what you are looking is reached.

I use 30psi and these methods for a soda water for a root beer or Dr. Pepper type thing.

For an IPA, larger or other (fizzy) beer I would use about 20psi but then it may be too much/not enough carbonation for some people, you will need to see what works best for you and your setup.

And for a proper ale or bitter I use about 5-10psi, just to evacuate the air over carbonating it.

Then once it is at the required carbonation level (by taste), I reduce the pressure on the CO2 bottle regulator and burp the keg to my serving pressure, about 10psi for soda water. my Russian imperial stout is quite 'thick' and chewy so need a higher pressure to push it out of the keg, about 20psi. but as I have said you will need to see what works best for you and your setup, pipe lengths, faucet and anything else it goes through will affect serving pressure, just take this as a starting guideline.

I would also say, keep things simple... pumps and the such will cause turbulence in the pipes and may be degassing your beer! also not really needed. All that cleaning, gasp

Bottom up... never done it, top down works and is easy/quick enough, yes there maybe 'better' more efficient ways that work for other people... it's all about what work best for YOU.

This guide has some good tables in it for CO2 by volume and carbonation chart (if you want the science) https://www.morebeer.com/themes/morewinepro/kegging.pdf

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For many years, I force carbonated using 30PSI and shaking the keg. It works, but the results are inconsistent and takes some effort to get the carbonation right.

Now that I am older and wiser, I use this method:

Saturation Over Time: The principal of this method is simple: If you leave constant pressure on the beer it will absorb the Co2 until the pressure pushing down on the beer equals the internal pressure of the gas dissolved in the liquid. Depending on the temperature and Final Gravity (F.G.) of the beer, beer will usually take an average of 5–10 days to stabilize.

  1. Hook the Gas-In Quick Disconnect to the Gas-In Body Connect and turn the gas on.
  2. Adjust your regulator to the desired PSI and let the beer sit at this pressure for 7–10 days.
  3. You can test your beer by pulling a pint off of the keg after 5–7 days.
  4. If the beer is under-carbonated to your taste, let it sit for another 1–3 days, testing periodically as necessary. The great thing about carbonating over time is you give your beer a period of cold aging while avoiding any chances of over carbonating, which can lead to excess foam and make serving beer very difficult. Although this method takes longer than the others, this is by far the easiest and least involved method.

I find that it pretty consistently takes about seven days to finish. Most of the beers that I make benefit from a couple more weeks maturing in the keg anyway, so I am not concerned with how long it takes to carbonate.

I have tried hooking the gas to the "out" post (to inject gas at the bottom of the keg), but I never noticed any difference in speed to final carbonation. Plus, this prevents you from sampling to see how things are going.

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