Make sure you have some kind of overflow system installed. You'd think one of those 55 gallon barrels would take a while to fill. Ha! You have a heavy rainstorm, and it will fill almost instantly. And a little garden hose will not handle the volume of overflow either. I would say something the size of 1" PVC at minimum is needed. You can buy overflow systems, or devise our own. Just don't neglect to install something.

You don't want the overflow bubbling out the top and running down near your house foundation, or onto your deck, or wherever you put the barrel. Ask me how I know this!