Appendix I — INSTALLATION STANDARDS
10.6 Sizing and Flow Velocities — 2025 California Plumbing Code
California Plumbing Code (Title 24, Part 5) · 2025 edition · updated 2026-10-19 · 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) § 10.6 · Effective January 1, 2026 · Official source: Building Standards Commission
10.6.1 PEX tubing shall be sized in accordance with IAPMO/ANSI UPC 1.
Note: Potable water piping sizing is addressed in Chapter 6 and Appendix A of IAPMO/ANSI UPC 1. 10.6.2 The tubing manufacturer’s pressure-loss data should be referenced when using Appendix A of IAPMO/ANSI UPC 1. In absence of such data, Figures 3 and 4 shall be used.
10.6.3 Flow velocities through the water distribution system, used for calculating flush tank and flush valve fixture units depending on the tubing sizes (see Table 1), shall not exceed
(a) 3.0 m/s (10 ft/s) for cold-water distribution systems; and (b) 2.4 m/s (8 ft/s) for hot-water distribution systems. Note: The flow velocities in Items (a) and (b) account for the increased velocities through the fit- tings. 10.6.4 Hot-water recirculation systems shall
(a) be balanced to maintain adequate system temperatures; and (b) have flow velocities that do not exceed 0.6 m/s (2 ft/s) (see Table 2); and (c) use only PEX tubing designated for hot, chlorinated water recirculation systems and rated for the maximum percentage of time during which the system is intended to be operated at elevated temperatures, in accordance with ASTM F876.
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