Different Carbonation Levels on a Single Manifold

Question

I have a Belgian Golden Strong and an American Brown that are both going into the same keggerator that share the same manifold. I would like to carbonate the Belgian at a higher value than the American Brown, but I am not sure how to maintain this level of carbonation with the shared manifold. It does have valves on each port so i can switch if needed, but I am looking for a "set it and forget it" method.

I typically set my CO2 pressure at about 20 and rock the keg for about 3-4 minutes then seal it off and let it sit for 24 hours or so to get the initial carbonation, but I don't understand (at least) two things:

1.) How can i really control the CO2 level for each in the initial carbonation and

2.) How can i maintain the proper levels after the initial carbonation with a shared manifold. Even if i get a separate regulator to allow a lower pressure on some beers, I have been led to believe that serving pressure is around 5-10 psi, and i don't see logically how a set psi can maintain variable levels of carbonation.

I do have one gas line on the manifold that is shorter (approx 3 feet) than the others (each approx 5 feet), so suppose I may be able to get close from what I understand about psi vs. gas line length, but I am looking for a more authoritative answer than "that might do what I want".

Any ideas/feedback?

Answer 1

I'll answer your questions out of order. To get different CO2 pressures, you need separate regulators. You can do it in two ways: I use a dual primary, like this one from Micro-Matic.

Your other option is to have one or more secondary regulators after your manifold or instead of a manifold.

For #1, in my opinion the best way is to just set it and forget it, instead of the high-pressure shake method. First you would find the appropriate volumes of CO2 for your two beers (let's say 2.4 for the Belgian and 2.0 for the Brown). Then, using a carbonation chart like this one, find out the pressure you need to keep on the kegs at the temperature in your fridge. I keep my fridge at 37-41F, so averaging that to 39F my pressures would be 7 and 11 PSI (those numbers seem a little low in my experience, so some experimentation may be needed).

Now in order to dispense without foam, you need to balance your lines. This means using appropriate serving line lengths and diameters to provide enough resistance to prevent foaming, but enough freedom for a good pour. Again, this may require some experimentation. In my system, I have 6', 3/16" diameter lines and serve and carbonate at 10-11 PSI. You can even find calculators online, like this one.