Residential Rainwater Harvesting Systems

What is a Rainwater Harvesting System? Rainwater harvesting is collected precipitation from rooftops and other above-ground impervious surfaces that is stored in catchment tanks for later use. Rainwater harvesting systems can range from a simple barrel at the bottom of a downspout to multiple cisterns with pumps and filtration. Rainwater is different than potable tap water and requires specific measures for its safe reuse in your garden.

Rainwater can be used to water all your plants – including edible plants and gardens. Untreated rainwater collection can only be for sub-surface outside irrigation.  

Benefits of Rainwater Harvesting: Berkeley averages roughly 20 inches of rain a year. That rainwater currently flows off your roof, into a stormdrain and out to the San Francisco Bay. Harvesting rainwater helps conserve water and can save you money on your water bill. Using rainwater to water your garden helps replenish local aquifers and reduces the amount of stormwater that drains into the Bay. The harvested water is low in sodium, and chloramine and fluoride free.
 
Types of Rainwater Harvesting Systems:
There are two main types of rainwater harvesting systems that vary in complexity, volume of water stored and permitting requirements.  In order to know which system is right for you, you need to determine your irrigation needs including yard size, soil type, groundwater level, current rainfall and your budget. The easiest, most low-tech system is a rain barrel attached to your downspout that has a spigot and hose out to your garden. 

Rain Barrel (Less than 100 gallons —no permit required) A rain barrel system is a simple rainwater collector that captures and stores a portion of the runoff from a roof downspout. A hose attached to the bottom of the rain barrel can be used to irrigate your garden. A rain barrel will only capture a small fraction of the rainwater that flows off your roof, the rest of the runoff will still need to drain to a safe overflow location. Rain barrels that follow all requirements set out by the City of Berkeley do not require permits.

Cisterns (Greater than 100 gallons) Cisterns are larger systems that can hold much more water and may include pumps to move the rainwater to the garden. More complex systems can involve plumbing and electrical work, soil excavation or other structural work. For rainwater collection projects of this scale, consult a professional to review design, construction and safety considerations. Permits and zoning certificates are required for cistern systems. 
For permitting information, see the City of Berkeley’s website at: www.cityofberkeley.info/planning

Permitting Requirements:

System Type

Plumbing Permit

Electrical Permit

Building Permit

Zoning Requirements

Rain Barrel (<100 gallons)

No

No

No

None

Cistern (<360 gallons)

Yes

No

No

Requires zoning certificate

Cisterns (>360 gallons)*

Yes

No

Yes

Requires zoning certificate

Cisterns >5000 gallons & >2:1 height to width OR Cisterns above grade (raised) OR below grade (underground)*

Yes

No

Yes 

Cisterns on or above grade require zoning certificate (none required for underground cisterns)

Cisterns within a building

Yes

No

No

None

Pumps added to any system

 

Yes

 

 

*Engineered drawings and calculations may be needed for anchoring of cisterns, seismic loading and, anticipated loading, depending on placement, seismic design category and size of cistern on a case by case basis.

To ensure health and safety, all rainwater systems must be:

Rain Barrels: No permit or city approval is needed for rain barrel systems of 100 gallons or less per vessel, provided all city requirements are met. Rainwater catchment systems over 100 gallons require permits and approval from the City of Berkeley Building Department.  

Rain Barrel System Requirements:

Resources and Links:

Rain Barrels and Cisterns (Bay Area Stormwater Management) Rain Barrels and Cisterns

American Rainwater Catchment System Association ARCSA

East Bay Municipal Utility District (EBMUD)

City of Berkeley Graywater Reuse Graywater Collection Systems 

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