Using your just your address, this rainwater collection calculator can tell you just how much rainwater you can collect off of your roof for use around your home. When you enter your street address in the calculator, you see your actual home from a birds-eye view above (via the built-in Google Maps capability). Once you have your house in view, you trace the roof line using your mouse to come up with the square footage available, which then calculates approximately how many gallons of water you can collect in an average rainfall year for your location. I put in my mother’s house, with 1,740 in available roof square-footage, and discovered that if she had a rainwater collection system in place, she could collect about 46,554 gallons in just a single year!
Of course, finding out that you can collect thousands of gallons of rainwater off your roof doesn’t do you much good if you can’t keep it long-term, right? You can use a rain barrel or two positioned under a gutter’s downspout and/or a cistern to keep your water stored for when you need it, and here are some more tips on harvesting rainwater for household use. Good luck, and save that rainwater!