Hard Root Beer in kegerator, what psi?

[my95tsi]

I just installed a 1/4 barrel of hard rootbeer into my kegerator and all seems to be working flawlessly. I'm new to kegerators and this is my first keg. My only question is what psi should i set the co2 at? I know beer is roughly around 12psi but i'm thinking this hard root beer should be higher. At 12psi it doesn't pour with much head but it still tastes carbonated, just slightly less carbonated than what i have had on tap at the bars. I heard that soda should be around 30psi so i'm not sure if i should crank it up that high. I did push it up to 18psi and it got better but i still feel it's not where it should be.

Any suggestions?

[KillianBoy]

my95tsi,

You really don't "guess" at PSI, read through following:

http://www.micromatic.com/forum/us-en/forum-guidelines-read-before-posting/6950-read-before-posting.html

CO2 Pressure Regulator Draft Beer

If you can't get v/v you can use this as the absolute last resort to balance beer:
Micro Matic Keg Beer Blog

I had this in my newbie thread, I cut out relevant part to make it easier:
To get the PSI to set, you get the v/v, if you can't find the particular beer listed in the Carbonation thread you at least have to know what brewery makes that beer. Most times big breweries (sometimes even small) carbonate all their beers the same across the board, mind you there a few exceptions, but generally all from one big brewery are the same. v/v isn't a reading, a setting or different way to set PSI.
You take this v/v to ANY carbonation chart (easily found on the 'net) I use the following, you don't have to use it but I find it convenient

TastyBrew.com | Homebrewing Calculators | Kegging Carbonation Calculator

18 PSI might be fine depending on temperature of the beer, definitely not 30+ (unless you are using mixed gas, if confused about mixed gas, look at my newbie thread).
So I assume you are applying pressure 24/7 on the beer, that you don't have 1st beer foam and you don't have a leak. My guess is you had PSI too low for temperature for several days and beer is slowly going flat, understand by upping PSI won't have immediate effects, if you had way too low it may take a while to get back to normal.
So contact brewery, buy a thermometer, and read through forum, if you still have problems, post back v/v, temperature of beer, modifications made on kegerator and how beer pours 1st-3rd consecutive beer.
KB