I have been brewing for a number of years, bottling most of my beer. I turned to kegging my beer about two years ago. Mostly, everything is fine, however, recently while carbing a batch of beer I didn’t notice a very small leak in the keg lid and over two days I lost 5lbs of CO2. Lesson learned, now it is checked carefully. I have two kegs in the frig, both carbed and set at a serving level. I was wondering if turning the CO2 off when not serving is a good idea or will I start to lose CO2 from the beer that’s in solution? Mild worry that if something leaks I can lose another 5lbs of CO2. Never turned it off before, just wondering.
Generally it's OK. You should only lose gas if there's a leak. This goes for whether the bottle is turned on or not. It's a closed system, the CO2 should stay at the same pressure, and thus dissolved.
Theoretically everything should stay in the much the same state. So there's no reason to leave your gas turned on (other than convenience).
Turning your gas off allows you to detect leaks too - without losing a bottle of CO2! Say the beer is all fully carbonated, and you turn your gas off. When you come back in a day/week/whatever, turn the gas on - nothing much should happen. But if you hear the noise of the the kegs re-pressurising, then you know something is leaking (somewhere).
Obviously if a beer is not already carbonated to serving pressure (or the temperature drops), you would expect this to happen, as the CO2 dissolves into the beer.
I did exactly this last night. Turned the CO2 on, the regulator "groans" for 30 seconds ... Hmmm, something is leaking.