San Mateo County, CA Landscaping Rules: Rainwater Harvesting (2026)

California's Rainwater Capture Act of 2012 (AB 1750) made residential rooftop rainwater harvesting broadly legal. Under California Water Code Section 10574, no state water-rights permit is required to capture and store rainwater from rooftops for outdoor non-potable uses when stored in a rain barrel or cistern under 360 gallons, and no notice to the public water system is required for cisterns under that size. Larger or potable/indoor systems may require plumbing permits and inspection from the County. San Mateo County actively promotes harvesting through the San Mateo Countywide Water Pollution Prevention Program (Flows To Bay), administered with BAWSCA. Its Rain Barrel Rebate provides tiered rebates available to ALL San Mateo County residents: $50 for 50-99 gallon systems, $100 for 100-199 gallon systems, and $150 for 200+ gallon systems (minimum 50-gallon capacity designed for rain capture). Residents in certain cities/water districts can receive an additional $50 per barrel, up to a $200 maximum for the largest systems. Limits are two rebates per single-family account (four for multi-family/commercial), applications must be filed within 90 days of purchase with the original receipt and post-installation photos. A separate Rain Garden Rebate of $300 is also available when added to a lawn-replacement project. These are voluntary incentive programs, not mandates.