Regulations for onsite treatment and reuse of nonpotable water (SBDDW-22-001)

The State Water Resources Control Board, Division of Drinking Water, has established regulations under Resolution No. 2025-0036 to govern the onsite treatment and reuse of nonpotable water within multifamily residential, commercial, and mixed-use buildings across California. These risk-based water quality standards are designed to protect public health while promoting the beneficial reuse of alternate water sources to reduce potable water consumption. The framework applies to Onsite Treated Nonpotable Water Systems that collect and treat alternate water sources for onsite use in buildings that rely on community sewer systems for waste discharge. Project proponents are required to provide comprehensive technical and design descriptions, including plans for monitoring, reporting, and contingency measures to prevent the delivery of inadequately treated water. Key deliverables include a validation study report and a commissioning plan, with the former requiring preparation by a California licensed engineer with at least five years of experience in drinking water or wastewater treatment. Additionally, cross-connection hazard assessments and backflow prevention testing must be performed by certified specialists. Compliance timelines require existing systems to meet these standards within two years of the effective date, with potential extensions up to five years granted by local jurisdictions. All operations must occur within the defined project boundaries as specified in the engineering reports.