I do like Mitch said but only leave one tank (cylinder) valve open. I then know when that tank runs out as my furnace and HW heater don't work. At that point I open the valve to the full tank and switch the regulator valve to the full tank side.
I always leave one tank valve closed because I don't check the regulator (Red/Green) gauge daily. If both valves were on and one tank runs out the regulator auto switches to the second. This happened to me a couple times where it auto switched to the full tank and ran out in the middle of a cold night and there I was with 2 empty tanks and a cold wife in the TT who was not happy with just me keeping her warm. Leaving one valve closed I know I have a full tank when the first runs out. For some reason my tanks always seem to run out in the middle of the night.
Definetly get the leak fixed. The soapy water works. I have found the o-ring seals dry out and crack as do hoses on my tanks.