1603.4 Minimum Water Quality — 2025 California Plumbing Code

The minimum water quality for harvested rainwater shall meet the applicable water quality requirements for the intended applications as deter- mined by the Authority Having Jurisdiction. In the absence of water quality requirements determined by the Authority Hav- ing Jurisdiction, the minimum treatment and water quality shall be in accordance with Table 1603.4, IAPMO IGC 324 or NSF/ANSI 350.

Exception [BSC] : No treatment is required for rainwater used for subsurface or nonsprinkled surface irrigation where the maximum storage volume is less than 5000 gallons (18 927 L) where the tank is supported directly upon grade and the ratio of height to diameter or width does not exceed 2 to 1.

1603.4.1 Disinfection. Where the initial quality of the collected rainwater requires disinfection or other treat- ment or both, the collected rainwater shall be treated as necessary to ensure the required water quality is deliv- ered at the point of use. Where chlorine is used for dis- infection or treatment, water shall be tested for residual chlorine in accordance with ASTM D1253. The levels of residual chlorine shall not exceed the levels allowed for the intended use in accordance with the requirements of the local enforcing agency.