When beer dries it is like glue. Take a glass of tepid water and pour over faucet to loosen this glue. You have a leak. Soap every fitting to determine where it is. A properly filled cylinder should read approx, 850 PSI at 70F enviroment and around 400-500 PSI at 38F. Same amount of gas and 5# should dispense close to nine half bbls if there are no leaks. You do not have this gauge to read. Upgrade to either a
double gauge regulator or purchase a
high side gauge .Not only are you loosing gas but it is difficult to set correct pressure with a leak. You can actually use the high side regulator to check for leaks. Later on that. Your beer will not go flat if you remove the coupler or turn off the gas at the cylinder. This is a sealed system ( after leaks are repaired) and carbonation cannot go anywhere. What causes flat beer is incorrect CO2 PSIG.
Scott Zuhse, Instructor
Micro Matic Dispense Institute