What is rainwater harvesting?
Rainwater harvesting is the practice of collecting and using rainwater from hard surfaces such as roofs. It is an age-old technology that is growing in popularity as people look for ways to use water resources more wisely. Communities in ancient Rome were designed with individual cisterns and paved courtyards, which captured rainwater to augment supply from the city’s aqueducts.
Until recently, urban areas served by municipal water have tended to overlook rainwater as a water resource. San Francisco would like to change that by raising awareness about rainwater harvesting and promoting its use.
Why harvest rainwater?
When you install a rainwater harvesting system at home, you are helping to maintain the health and beauty of San Francisco’s urban watershed in many ways. By harvesting rainwater you:
- Keep relatively clean water out of the combined sewer system and make it available for use
- Reduce the energy and chemicals needed to treat stormwater in San Francisco’s combined sewer and the energy expended transporting water from far away
- Reduce the volume and peak flows of stormwater entering the sewer, thereby reducing flooding and combined sewer overflows
- Reduce the volume of potable water used for non-potable applications such as irrigation and toilet flushing
- Rain Barrels: You don’t need a permit to install a rain barrel if your downspout is disconnected from the combined sewer system. If it’s connected, you’ll need a permit from the Department of Building Inspection.
- Cisterns: To install a cistern for irrigation or toilet flushing, you’ll need a plumbing permit and a building permit from the Department of Building Inspection, Plumbing Division. If your system includes a pump or will be installed on the roof or underground, you’ll need additional permits. The cistern installation permit process requires submission of a site plan of existing and proposed site conditions and proposed rainwater harvesting system elements.
For more information please visit the Department of Building Inspection’s website at: http://sfdbi.org or call (415) 558-6570.
We have put together a number of helpful resources, including a calculator to help you size your rainwater system, a how-to video, and instructional brochures and handouts.
"Making Your Own Closed-Top Rain Barrel System"
More Rainwater Harvesting Materials
Related Programs: Gardens and Landscapes
Green Dean TV: Installing a Rain Harvester
YouTube: Rain Water
Our Discounted Rain Barrel and Cistern Program is currently not in place. If you want to be added to our mailing list to be notified when the subsidy program starts again, please sign up here.