When dispensing keg draft beer, the goal is to keep the CO2 level prescribed by the brewer. Any change in the CO2 level will alter the taste, pouring characteristics and appearance of the beer.
Most breweries in the U.S. recommend a CO2 pressure between 12-14 lbs for Ale and Lager types of draft beers. This CO2 pressure will maintain the level of carbonation specified by the brewery. If you are unsure what the recommended CO2 pressure is for the beer you are dispensing is, simply inquire with the company you are purchasing your kegs from. If they do not know, they can make a quick call to the beer distributor or brewery to find out this information for you.
As there are literally tens of thousands of breweries and brands of draft beer available, it's simply not possible for Micro Matic to maintain a listing of the proper CO2 pressure for every brand of draft beer.
If the draft beer is dispensed with too low of a pressure, the CO2 that is dissolved in the beer will “break out” of the beer. Initially this will cause the small bubbles of broken out CO2 to float up the beer hose which will result in foamy beer. And over time the low pressure will result in flat beer.
If the draft beer is dispensed with too high of a pressure, over time more CO2 will be absorbed into the beer. Initially, this will not cause any problems, but over time this will result in over-pressurized foamy beer.