Chapter 16 — NONPOTABLE RAINWATER CATCHMENT SYSTEMS
1603.9 Drainage and Overflow — 2025 California Plumbing Code
California Plumbing Code (Title 24, Part 5) · 2025 edition · updated 2026-09-25 · California
CBSC: official editions, supplements and errata
Italicized text is a California amendment to the model code, as printed in the official publication.
Cite as: 2025 California Plumbing Code (Title 24, Part 5) § 1603.9 · Effective January 1, 2026 · Official source: Building Standards Commission
Rainwater storage tanks shall be provided with a means of draining and cleaning. The overflow drain shall not be equipped with a shutoff valve. The overflow outlet shall discharge in accordance with this code for storm drainage systems. Where discharging to the storm drainage system, the overflow drain and tank drain shall be protected from backflow of the storm drainage system by a backwater valve or other approved method. Back- water valves shall be installed so that access is provided to the working parts for service and repair.
1603.9.1 Overflow Outlet Size. The overflow outlet
shall be sized to accommodate the flow of the rainwater
entering the tank and not less than the aggregate crosssectional area of inflow pipes.
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