Los Angeles is a paradox. Our two defining infrastructures are the aqueduct system that imports water from across the state at a staggering environmental cost, and the LA River – a concretized channel designed to move rainwater as efficiently as possible out of our city to the ocean.
Does it make sense to capture rainwater in Los Angeles? Absolutely! Consider that due to the large area of a typical collection surface (i.e., a roof), it doesn’t take much rain to generate a lot of water. One inch of rain falling on a 1,000 square foot roof adds up to 600 gallons! And the yearly average rainfall in L.A. is 15 inches.
15 inches of rain on that small roof could yield around 10,000 gallons of pure, clean rainwater – if you had the storage capacity to capture it. That’s why we generally recommend that people go large. A few 50 gallon barrels scattered around the property are nice, but they will rapidly fill up and overflow with only a minor shower.
Rainwater holds several great advantages over greywater. You don’t have to use it immediately; with proper prefiltration it can stay in the tank for months until you need it. It’s also nice to have a source of backup water for earthquakes or other emergency use. It’s also great for native plants, which can be challenged by micronutrients in greywater.