I had an interesting conversation with my LHBS associate the other day about keg pressure. It came up that I keep my kegs at carbonating pressure and he was adamant that after a week I should kick it down to "serving pressure". For example, I currently have a Belgian Tripel in my keggerator. Keggerator is set at 40º and my pressure on that beer is 20psi (looking to carbonate a little over 3 volumes). His suggestion was to bring it down to 10psi after a week. As I understand it, theoretically, there's an equilibrium at which CO2 will absorb into my beer – based on gravity, temperature and pressure. If I lower my CO2 to "serving pressure" won't it loose carbonation over time because that equilibrium is no longer met and CO2 can escape? Or, am I wrong and the truth is that keeping my beer at 20psi will only over-carbonate my beer?
simple test that commercial brewer use: wait a few days after the initial carb. @ 20psi. start taking samples every 12 hours or so. once the bubbles rise very quickly to the head, its fully carbed and you can lower to serving pressure depending on what you want that to be. I usually go around 10 psi. until the bubbles immediately rise to the top, keep at the 20psi. simple.
I picked up a Perlick flow control faucets. I run at 15psi with the kegerator set at 37F with appr 5' lines. The flow control faucets give me a lot of flexibility for foam and carbonation.
You're absolutely correct that you'll lose carbonation if you reduce the pressure below what's necessary to keep the beer carbed at the desired level. You mention 'carbonating pressure' and 'serving pressure'. Actually, the only thing people agree on is 'serving pressure'. Using any number of widely available charts, you use your desired volumes of CO2 and temperature to find the correct serving pressure. That's it. The beer will be perfectly carbonated in ten days or so if you set the regulator to the indicated serving pressure. No surprises. Using a higher pressure to carbonate it more quickly is usually referred to as 'force carbonating' though that term actually refers to carbonating with a tank of CO2 instead of a dose of priming sugar - semantics. Using a higher pressure like this is a crap shoot. Unless your pipeline is dry, I would recommend forgetting about 'carbonation pressure' as a thing. Just use serving pressure.
I picked "I keep it at carbonation pressure and adjust tap line" because that's what I used to do, i.e. used a line length that balanced the set-and-forget pressure that provided the volumes of CO2 I wanted at the fridge temperature. But now I use flow control faucets, which accomplishes the same thing. i.e. it dials-in the resistance needed to balance against the pressure that maintains the CO2 level.
Now that I have a few kegs flowing I just keep the same pressure, about 10 psi. Yes it takes a few days longer to carb the beer but I haven't had to adjust my regulator in a while. My home brew kegs flow perfectly while my sanke commercial keg runs a little fast at times. All my beers are ipa's or pale ales so they are very similar. I stick to and brew what I like.
My 'serving' regulator (as opposed to my 'utility' regulator that I use for purging, transferring, pushing fizzier beers, etc) never gets touched. The last time I tried to adjust it, the knob was stuck. I had to use pliers to turn it. Once you dial in your system, it'll run itself. It may take a few months to get there, but it'll happen.
