CO2 and sealing question?

This is one thing that I just can't understand. Assuming that the keg is completely sealed and not leaking, once you carb the keg to your desired volumes of CO2, why do you need to keep it on the gas? If the Co2 is in the solution and the keg remains cold, shouldn't it stay? Isn't this the basis of bottling and canning?

If I am completely off base and this is not the reason to keep the kegs on gas, could someone enlighten a kegging newb? Thanks!

Jason

You're correct. Until you go to serve it, that is. However, a perfectly sealed keg is hard to come by unless you replace all the rubber when you get it.

I assume you mean as you dispense your brew. As the volume beer in the keg decreases additional C02 must replace the poured beer - to maintain the same pressure. If the pressure in the keg drops then some of the C02 would come out of solution to fill the additional volume - decreasing the carbonation. Otherwise then it must be leaking.