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Rainwater Harvesting Systems
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.
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.