Check List
"PROPANE: Do not turn on both tanks at the same time. Use from one tank at a time so that when one is empty, you will still have another full one to use. Promptly refill the empty one and you should never run out of propane."
Good list, but must disagree with Propane: If your first tank runs out in the middle of a rain storm, or while take a shower, you have to go out and turn on the full tank. A better solution is to turn on both tank, and check periodically. When you see the first tank is empty, fill it.