How Much Water Can You Collect From Your Roof?
Jason Marshall, PhD
Have you ever wondered how much water falls on your roof when it rains? Are you wondering why you’d ever want to wonder about that in the first place? Well, the reason it’s an interesting question is that the roof of a modestly sized house has the potential to collect a pretty impressive amount of water in a storm. And that’s all water that can later be used in the garden…for free!
There’s lots of information about the nuts and bolts of redirecting water from your gutters into rain barrels online (including information about where to use the water and how to make sure it’s safe to do so), so we won’t talk about that here. But there’s one interesting bit of math related to this topic that we will talk about. Namely, a handy conversion that you can use to quickly find out how much water you can potentially collect from your roof. Here’s the formula:
- Gallons collected per inch of rainfall ≈ 0.62 • total collecting area of roof in square feet
So if you have a 1,000 square foot house, you can potentially collect 0.62 • 1,000 = 620 gallons of water every time it rains an inch. With two inches of rain, you can collect around 1,240 gallons. And every bit of that is free water for you to use in your yard!
Image courtesy of Shutterstock
About the Author
Jason Marshall is the author of The Math Dude’s Quick and Dirty Guide to Algebra. He provides clear explanations of math terms and principles, and his simple tricks for solving basic algebra problems will have even the most math-phobic person looking forward to working out whatever math problem comes their way.