During a stay at my in-laws their pool cover collected about three inches of water in a massive rainstorm. My brother-in-law said we'd have to remove the rainwater before it leaked into the pool, and in my head I got busy concocting a complex siphon using a garden hose filled with water that would run down a hill into their neighbor's yard. I was about to explain the theory behind this device when he walked out of the garage carrying an electric pump and long extension cord. It worked very well, and no one had to string a hose over the embankment into the neighbor's place. Everyone wins.