Keg beer typically has too much foam because of a temperature problem, usually because the keg is too warm. The bottom of a kegerator or other draft beer dispenser must be less than 40 degrees Fahrenheit for beer to dispense properly. If a long-draw system is being used, the coolant should be within a degree or two of freezing, or 32 degrees Fahrenheit.
If keg beer comes out too foamy, the first thing a brewer or bartender should do is check the temperature of the keg or kegerator. It is important to check the temperature of the liquid, rather than the temperature of the air. The foam problem can be eliminated either by cooling the draft tower, if the floor of the kegerator is indeed below 40 degrees Fahrenheit, or by increasing the circulation of cold air within the refrigerator or box holding the keg. On those rare occasions when lack of cold temperature is not the problem, the bartender should make sure that the keg is full, that a new keg has had time to settle, that the tap is fully opened and that the pressure on the regulator is set correctly. If the regulator pressure is over 14 pounds per square inch, it should be lowered. If all these steps are taken and the beer being dispensed is still too foamy, there is probably a mechanical problem with the brewing system.