Yes, rainwater collection is legal in California. The Rainwater Capture Act of 2012 lets any residential, commercial, or governmental property owner capture rain that falls on their rooftop without obtaining a water right permit from the State Water Resources Control Board. There is no state cap on how much you can collect. What varies is the paperwork: a rain barrel feeding a garden needs almost nothing, while a system plumbed into your toilets or treated for drinking triggers building permits, health department review, and ongoing inspections.
The Law That Made It Legal
Assembly Bill 1750, signed in 2012, created the Rainwater Capture Act and codified it in the California Water Code starting at Section 10571. Its central provision is that collecting rainwater from a rooftop is not a diversion that requires a water right permit.1California Legislative Information. California Code, Water Code WAT 10574 Before the Act, California’s water rights system created uncertainty about whether capturing rain counted as diverting a water resource. The law resolved that question for developed and developing land.
The Act authorizes rain barrel systems, outdoor non-potable capture systems, and indoor non-potable capture systems.2California Legislative Information. California Assembly Bill 1750 – Rainwater Capture Act of 2012 It does not change existing water rights, override local building authority, or cover rainwater use on agricultural lands.3California Legislative Information. California Code WAT Division 6 Part 2.4 10573 The California Building Standards Commission still writes building code requirements for these systems, and local agencies still issue permits for more complex installations.
What Counts as Rainwater
The Water Code defines rainwater as precipitation falling on a public or private parcel that has not yet entered an offsite storm drain, flood control channel, or stream, and has not previously been put to beneficial use.3California Legislative Information. California Code WAT Division 6 Part 2.4 10573 Once water leaves your property into a storm drain or channel, it is no longer rainwater under the Act and falls under separate stormwater rules.
A rainwater capture system means a facility designed to capture, retain, and store rainwater flowing off a building rooftop for later onsite use. A rain barrel system is a narrower subset: it uses no electricity or pump and is not connected to a potable water system.3California Legislative Information. California Code WAT Division 6 Part 2.4 10573 That distinction drives the lightest permit treatment under the Act.
What You Can Install Without a Permit
A rain barrel used only for outdoor, non-potable purposes, such as watering a garden, is the simplest setup. The Rainwater Capture Act states that a landowner cannot be required to obtain a permit from a local agency as a condition of operating a rain barrel system that complies with the Act.4Legislative Counsel of California. AB 1750 Assembly Bill – Bill Analysis If your barrel uses no pump, no electricity, and no connection to your home’s plumbing, you can install it without filing anything. Systems storing less than 360 gallons for irrigation or car washing also face no minimum water quality requirements.5U.S. Environmental Protection Agency. Summary of California’s Water Reuse Guideline or Regulation for Rainwater Collected Onsite for Landscaping and Non-potable Water Reuse
When Permits Kick In
The rules get stricter as the system gets more complex or the water moves closer to indoor use.
Larger Outdoor Systems
A cistern with a pump feeding a drip irrigation network goes beyond the rain barrel exemption. These installations may require building permits depending on your local jurisdiction. Untreated rainwater used only for surface, subsurface, or drip irrigation is regulated under Chapter 16 of the California Plumbing Code (Cal. Code Regs. tit. 24, ยง 5).5U.S. Environmental Protection Agency. Summary of California’s Water Reuse Guideline or Regulation for Rainwater Collected Onsite for Landscaping and Non-potable Water Reuse
Indoor Non-Potable Systems
Plumbing captured rainwater into toilets, laundry, or similar non-drinking fixtures triggers more oversight. These systems must be permitted and inspected by the local agency with jurisdiction, which must consult with the local public health department before issuing the first permit and may impose additional conditions. A second inspection under building standards enforcement is required before the system can be used.4Legislative Counsel of California. AB 1750 Assembly Bill – Bill Analysis Systems supplying toilets and urinals must include a debris excluder plus a 100-micron filter. Where no local rules exist, a default water quality standard applies: E. coli below 100 CFU per 100 mL and turbidity below 10 NTU.5U.S. Environmental Protection Agency. Summary of California’s Water Reuse Guideline or Regulation for Rainwater Collected Onsite for Landscaping and Non-potable Water Reuse
Potable Systems
Treating captured rainwater for drinking is the most heavily regulated option. A permit is required, and the system cannot have a direct connection to a public or private potable water supply or alternate water source. On initial startup, the local authority having jurisdiction (typically a plumbing, mechanical, or building official) determines whether the treated water meets quality standards for its intended use. Potable water filters must comply with NSF/ANSI Standard 53 and be installed per the manufacturer’s instructions. If potable water from a public supply is used as makeup water for the storage tank, the connection must be protected by an air gap or backflow preventer. Inspection and maintenance follow the schedule in California Plumbing Code Table K 101.5.1 unless the manufacturer requires more frequent servicing, and the owner must keep a maintenance log on site.6U.S. Environmental Protection Agency. Summary of California’s Water Reuse Guideline or Regulation for Rainwater Collected Onsite for Potable Water Reuse
No Volume Limit, but Size Drives Code
California puts no cap on the gallons you can collect. There is no maximum tank size in state law, and no volume threshold alone triggers extra permits. What changes with scale is the building and plumbing code. A 55-gallon barrel under a downspout needs nothing. A 5,000-gallon underground cistern with pumps and filtration involves structural engineering, building permits, and plumbing inspections regardless of how you plan to use the water.
What About HOAs
If a homeowners association governs your property, California law generally protects water-efficient landscape features in common interest developments under Civil Code Section 4750. The statute’s primary focus is drought-tolerant landscaping, but its protections extend broadly enough that an HOA would have difficulty flatly prohibiting a properly installed rain barrel used for landscape irrigation. An HOA can still enforce reasonable aesthetic requirements, including where the barrel sits and how it is screened from view. Citing both the Rainwater Capture Act and Civil Code Section 4750 usually resolves disputes.
Rebates From Local Water Agencies
Several California water agencies offer rebates that offset equipment and installation costs. Programs vary by region and change periodically, so check with your local provider before buying.
- San Francisco Public Utilities Commission pays up to $100 per rain barrel (two barrel maximum) or up to $350 for a single cistern between 205 and 5,000 gallons.7San Francisco Public Utilities Commission. Rain Barrel and Cistern Rebate
- The Bay Area Water Supply and Conservation Agency offers up to $100 for barrels holding 50 to 99 gallons, up to $150 for 100 to 199 gallons, and up to $200 for 200 gallons and up, with participating San Mateo County member agencies contributing additional funds through June 2026.8BAWSCA. Rain Barrels
- Santa Clara Valley Water offers rebates for rain barrels, cisterns, and rain gardens for customers with existing gutters or downspouts not currently capturing rainwater.9Santa Clara Valley Water. Rainwater Capture Rebate
Many other water districts run similar programs. As of 2026, there is no statewide tax credit specifically for residential rainwater harvesting in California; the financial help is almost entirely local rebate money.
Design and Maintenance That Keep You Compliant
California’s wet-season-only rainfall makes system sizing matter. Most precipitation falls between November and March, so storage needs to be large enough to carry water into the dry months. A 1,000-square-foot roof in an area receiving 15 inches of annual rainfall can yield roughly 9,000 gallons per year, nearly all of it arriving in a few months.
Routine upkeep is simple. Clean gutters and downspout filters at least quarterly. Drain first-flush diverters after each rain event. Wash tank interiors annually with a non-toxic detergent, and remove sediment buildup once it exceeds an inch.
Mosquito prevention is a legal requirement rather than a nice-to-have. Every opening on a barrel or cistern, including the inlet, overflow outlet, and any inspection port, must be covered with fine mesh screening. Local mosquito abatement districts actively enforce against standing water that produces mosquitoes, so a purpose-built rain barrel with sealed openings is a better starting point than a repurposed open container.