Marin County, CA Landscaping Rules: Rainwater Harvesting (2026)
Key Facts
- Allowed use
- Listed accessory use, § 22.130.030
- Detached height cap
- 16 ft above grade
- Setback exemption
- 18 inches or less above grade
- Rear setback cap
- 10 ft, equal to side setback
Summary
Unincorporated Marin's Development Code lists rainwater cisterns and collectors, alongside solar collectors and storage sheds, as an allowed residential accessory use. A free-standing cistern or collection structure counts as a detached accessory structure, capping its height at 16 feet and putting it under the same rear and side setback rules as other outbuildings.
Residential Accessory Uses and Structures (land use). This land use consists of and includes any use that is customarily a part of, and clearly incidental and secondary to, a residence and does not change the character of the residential use. These uses include the following accessory structures, and other similar structures and uses normally associated with a residential use of property: - garages - gazebos - greenhouses - spas and hot tubs - roof-mounted WECS - solar collectors - rainwater cisterns and collectors - storage sheds - studios - swimming pools - workshops.... B.Detached accessory structures. A detached accessory structure shall not exceed 16 feet in height above grade. However, a detached accessory structure may be constructed to the height allowed for primary structures, by the applicable zoning district, if the accessory structure is located at least 40 feet from all property lines.... D.Exemptions from setback requirements. The minimum setback requirements of this Development Code apply to all development except the following: 1.Development that is equal to or less than 18 inches above grade;
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Municipal Code: Supplement 2026 Update 1).
Full Breakdown
030, define 'Residential Accessory Uses and Structures' to include rainwater cisterns and collectors in the same list as garages, gazebos, greenhouses, spas and hot tubs, roof-mounted wind energy systems, solar collectors, storage sheds, and workshops. 130. Where the collection system is a detached structure, such as a stand-alone cistern or tank, it must meet the same physical standards Marin applies to other detached accessory structures. 060(B) caps a detached accessory structure's height at 16 feet above grade, unless it sits at least 40 feet from every property line, in which case it can rise to the height allowed for a primary structure.
090 sets the setbacks: a detached accessory structure's rear setback must equal the required side setback, capped at 10 feet (20 percent of lot depth, up to 25 feet, on a through lot), and it otherwise follows the same side and front setbacks the zoning district requires for the primary structure. 090(D)(1), which lets a low-profile rain-collection basin or cistern sit close to a property line without triggering the accessory-structure setback rules.
Violations & Fines
A detached rainwater cistern or collection tank built taller than the 16-foot accessory-structure height limit, or placed inside the required rear or side setback without qualifying for the 18-inch exemption, is a Development Code violation the Community Development Agency can require the owner to correct, remove, or bring into compliance through a Design Review or Variance application.
Frequently Asked Questions
Do I need a permit to install a rainwater cistern on my property in unincorporated Marin?
How tall can a free-standing rainwater tank be?
Can I put a cistern close to my property line?
Sources & Official References
Other rules in Marin County
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