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

027(a) sets the county's default rule for every abandoned cesspool or septic tank: the sewage must be removed and the tank completely filled with earth, sand, gravel, concrete, or other approved material. The section then creates a named exception allowing the tank to be repurposed as a rainwater storage cistern instead of being filled in, conditioned on a numbered list of requirements. The property owner must first obtain a system abandonment permit from the county building department stating the tank's intended reuse, and the tank must be disconnected from both the drain field and the building sewer pipe by a registered septic tank contractor, state-licensed plumber, or the owner-occupant.

All septage and wash water removed during the conversion must go to an approved disposal service. 0 ppm, total coliform under 1,000 per 100 mL, and fecal coliform under 200 per 100 mL. One inspection is included in the abandonment permit fee, but the applicant pays for any additional re-inspection visits and all laboratory sampling fees. The abandonment permit is valid twelve months, and the tank may not be connected to irrigation, or its water used for irrigation, until final approval; once approved, the collected water may be used only for non-potable irrigation, never reconnected to sewage storage, treatment, or disposal.