Cisterns are roof water management devices that provide retention storage volume in above-ground or under-ground tanks. By harvesting large amounts of rainwater, cisterns aid in preventing stormwater pollution by diverting rainfall from roofs and reducing the undesirable impacts of runoff that would otherwise flow swiftly into gutters and storm drain systems contributing to flooding and erosion problems in creeks. Cisterns are preferable for commercial or residential properties that wish to irrigate larger landscapes or water intensive gardens that for an average single-family property. Depending on the size of the cistern, users may have a lower utility bill if enough rainwater is used as an alternative to potable water.

STEP 1 – APPLICATION SUBMITTAL

1. Read and agree to the City of Palo Alto Terms and Conditions listed on the Stormwater Rebate homepage.
2. Create a Valley Water application portal account. (For applicants who cannot access the online portal, a hard copy is available upon request by calling the Water Conservation Hotline at (408) 630-2554, or emailing conservation@valleywater.org).
3. Complete the Stormwater Rebate Application in the portal and attach all required documents.

• Taxpayer information (taxpayer name, contact info, mailing address)
• Site information (address, site type, water account number)
• Initial Proposed Project (including photos of the proposed landscape/existing equipment to upgrade or photos of the existing downspouts)

STEP 2 – APPLICATION AND DESIGN REVIEW 

1. Valley Water and Watershed Protection staff receive the application and attached documents, including the proposed design. Applicants will be contacted to confirm the retrieval of their application information.
2. Some projects may require a permit to install. To inquire about permitting, please contact the Development Center at 650-329-2496 and select Option 3 for Building Plan Check Team when prompted. (Please note, do due Shelter in Place order, Planning and Development Services staff are working remotely. Please refer to the Development Center page for more information).
3. Staff will contact the applicant to request additional information if deemed necessary and to set up a pre-inspection.
4. Staff will perform a pre-inspection of the site where the cistern will be installed.
5. A “Notice to Proceed” will be issued from Valley Water prior to installation of your cistern.
   

1. Purchase and install cistern per specifications on submitted application.
2. Notify Valley Water through the application portal once the cistern has been fully installed. Arrange a post-inspection with staff.
3. Cistern must be inspected by Watershed Protection staff upon completion.

STEP 4 – FINAL DOCUMENTATION

1. Submit all documentation through the Valley Water rebate application portal (if not previously submitted, including IRS Form W-9).
2. Receive rebate payment from Valley Water within 6-8 weeks of final approval.

Cisterns can be installed above-ground or under-ground depending on their size. Though under-ground installation can be more costly, many prefer it for aesthetic reasons. When choosing to install an under-ground cistern, there are many factors to consider. These factors include factors like buoyancy and maintenance.

Above-ground cisterns typically have a screened opening that permits water from a downspout to enter the storage tank, some form of an overflow mechanism, and a spigot.

• Cisterns usually have a screen over its opening to prevent mosquitos and other insects from entering the tank.
• The spigot allows access to the water stored in the barrel. The spigot can be kept partially open to retain water from the barrel or closed to store more water. The spigot can also be connected to a hose for pressurized irrigation systems.
•  The overflow pipe releases excess rainwater that cannot be stored in the barrel. Overflow pipes can be connected to adjacent rain barrels for higher storage capacity or directed into pervious surfaces like gardens for irrigation.
•  The vent cap allows fresh air to circulate through the cistern’s storage compartment and through the vent pipe.

Cisterns may also contain features like pumps to allow easier access to the harvested water. It is common to find cisterns of different materials such as concrete, plastic, polyethylene, or metal.

Under-ground Cistern Diagram

Above-ground Cistern Diagram

All under-ground cisterns require approval or permitting from the Development Center. Any cistern with a pump, backflow device, or other feature that may be automatic (including an irrigation system) will require a building permit. If a cistern is over 5,000 gallons, it will also require a building permit. Although it is not recommended, cisterns connecting to potable water will also need a building permit. To inquire about permitting, please contact the Development Center at 650-329-2496 and select Option 3 for Building Plan Check Team when prompted. (Please note, due Shelter in Place order, Planning and Development Services staff are working remotely. Please refer to the Development Center page for more information).

The Bay Area Stormwater Management Agencies Association (BASMAA) has published a guide to understanding, installing, and maintaining cisterns and rain barrels. Applicants can access this maintenance guide for Rain Barrels and Cisterns online. BASMAA makes the following recommendations:

• Regularly check the gutters and gutter guards to make sure debris is not entering the rainwater harvesting system.
• Inspect the screens on the rain barrel or cistern prior to the wet season to make sure debris is not collecting on the surface and that there are not holes allowing mosquitoes to enter the cistern. Inspect screens more frequently if there are trees that drop debris on the roof.
• Clean out debris from cisterns once a year, preferably at the end of the dry season.

The City is not responsible for damage to property or injury of applicants, contractors, or property owners because of the recommendations of BASMAA. The City reserves the right to conduct a post-inspection of a rebate project to ensure that the system is running properly.

Cisterns require design review and approval by the Watershed Protection Group staff prior to the start of work to be eligible for a rebate. In certain circumstances during this review, the City may wish to do a pre-inspection of a property before installation of a cistern. If this is necessary, applicants will be contacted to set up an inspection.

• Seattle RainWise Cistern Maintenance Guide
  This guide produced by Seattle’s RainWise rebate programs details maintenance recommendations for cisterns. The City of Palo Alto is not responsible for any damage or construction mistakes as the result of an unlicensed contractor or DIY installation.
•  BASMAA Rain Barrel and Cistern Fact Sheet
  This short guide offers additional information about rain barrels and cisterns to guide new users’ maintenance. The City does not take responsibility for the material and recommendations made in this resource.
• City of Portland Cistern Fact Sheet
  This fact sheet provides additional information on above-ground and under-ground cisterns. This resource offers additional images of under-ground cisterns. The City does not take responsibility for the material and recommendations made in this resource.
•  Rescape Qualified Professionals Directory
  Rescape regularly updates a directory of local contractors that have completed any of their qualifying trainings. These trainings use a sustainable, holistic approach to the design and management of a landscape. They work with nature to conserve water and soil, reduce waste, and prevent pollution. You can find a Rescape Qualified Professional near you in this directory. The City is not responsible for any damage or construction mistakes as a result of an unlicensed contractor or DIY installation.