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Chapter 6 — WATER SUPPLY AND DISTRIBUTION

602.3 Backflow Prevention.

California Plumbing Code (Title 24, Part 5) · 2025 edition · updated 2026-09-12 · California

Italicized text is a California amendment to the model code, as printed in the official publication.

No plumbing fixture, device, or construction shall be installed or maintained, or shall be connected to a domestic water supply, where such installation or connection provides a possibility of polluting such water supply or cross-connection between a distributing system of water for drinking and domestic purposes and water that becomes contaminated by such plumbing fixture, device, or construction unless there is provided a backflow prevention device approved for the potential hazard.

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▸Contents — California Plumbing Code (Title 24, Part 5)
California Plumbing Code (Title 24, Part 5)
  1. Chapter 1 — GENERAL CODE PROVISIONS
  2. Chapter 2 — DEFINITIONS
  3. Chapter 3 — GENERAL REGULATIONS
  4. Chapter 4 — PLUMBING FIXTURES AND FIXTURE FITTINGS
  5. Chapter 5 — WATER HEATERS
  6. ▸Chapter 6 — WATER SUPPLY AND DISTRIBUTION
    Overview
    1. 601.1 Applicability.
    2. 601.2 Water Supply and Flushing.
    3. 601.3 Identification of a Potable and Nonpotable Water System.
    4. 601.4 Schools of Cosmetology and Cosmetological
    5. 601.5 Meat and Poultry Processing Plants.
    6. 601.6 Collection Centers and Facilities. [AGR]
    7. 601.7 Renderers. [AGR]
    8. 601.8 Horse Meat and Pet Food Establishments. [AGR]
    9. 602.1 Prohibited Installation.
    10. 602.2 Cross-Contamination.
    11. 602.3 Backflow Prevention.
    12. 602.4 Approval by Authority.
    13. 603.1 General.
    14. 603.2 Approval of Devices or Assemblies.
    15. 603.3 Backflow Prevention Devices, Assemblies, and Methods.
    16. 603.4 General Requirements.
    17. 603.5 Specific Requirements.
    18. 604.1 Pipe, Tube, and Fittings.
    19. 604.2 Lead Content.
    20. 604.3 Copper or Copper Alloy Tube.
    21. 604.4 Hard-Drawn Copper or Copper Alloy Tubing.
    22. 604.5 Flexible Connectors.
    23. 604.6 Cast-Iron Fittings.
    24. 604.7 Malleable Iron Fittings.
    25. 604.8 Previously Used Piping and Tubing.
    26. 604.9 Epoxy Coating.
    27. 604.10 Plastic Materials.
    28. 604.11 Solder.
    29. 604.12 Flexible Corrugated Connectors.
    30. 604.13 Water Heater Connectors.
    31. 605.1 Copper or Copper Alloy Pipe, Tubing,
    32. 605.2 CPVC Plastic Pipe and Joints.
    33. 605.3 CPVC/AL/CPVC Plastic Pipe and Joints.
    34. 605.4 Ductile Iron Pipe and Joints.
    35. 605.5 Galvanized Steel Pipe and Joints.
    36. 605.6 PE
    37. 605.7 PE-AL-PE Plastic
    38. 605.8 PE-RT.
    39. 605.9 PEX
    40. 605.10 PEX-AL-PEX Plastic Tubing and Joints.
    41. 605.11 Polypropylene (PP) Piping and Joints.
    42. 605.12 PVC
    43. 605.13 Stainless Steel Pipe
    44. 605.14 Slip Joints.
    45. 605.15 Dielectric Unions.
    46. 605.16 Joints Between Various Materials.
    47. 606.1 General.
    48. 606.2 Fullway Valve.
    49. 606.3 Multidwelling Units.
    50. 606.4 Multiple Openings.
    51. 606.5 Control Valve.
    52. 606.6 Accessible.
    53. 606.7 Multiple Fixtures.
    54. 606.8 [OSHPD 1, 1R, 2, 3, 4 & 5]
    55. 606.9 Check Valve Required.
    56. 606.10 Leak Detection Devices.
    57. 607.1 General.
    58. 607.2 Private Well Water Tanks.
    59. 607.3 Potable Water Tanks.
    60. 607.4 Venting.
    61. 607.5 Overflow.
    62. 607.6 Valves.
    63. 608.1 Inadequate Water Pressure.
    64. 608.2 Excessive Water Pressure.
    65. 608.3 Expansion Tanks, and Combination Tempera-ture and Pressu…
    66. 608.4 Pressure Relief Valves.
    67. 608.5 Discharge Piping.
    68. 608.6 Water-Heating Devices.
    69. 608.7 Vacuum Relief Valves.
    70. 609.1 Installation.
    71. 609.2 Trenches.
    72. 609.3 Under Concrete Slab.
    73. 609.4 Testing.
    74. 609.5 Unions.
    75. 609.6 Location.
    76. 609.7 Abutting Lot.
    77. 609.8 Pumps.
    78. 609.9 Low-Pressure Cutoff Required on Booster Pumps for Water …
    79. 609.10 Disinfection of Potable Water System.
    80. 609.11 Water Hammer.
    81. 609.12 Pipe Insulation.
    82. 610.1 Size.
    83. 610.2 Pressure Loss.
    84. 610.3 Quantity of Water.
    85. 610.4 Sizing Water Supply and Distribution Systems.
    86. 610.5 Sizing per Appendices A, C,
    87. 610.6 Friction and Pressure Loss.
    88. 610.7 Conditions for Using Table 610.4.
    89. 610.8 Size of Meter and Building Supply Pipe Using Table 610.4.
    90. 610.9 Size of Branches.
    91. 610.10 Sizing for Flushometer Valves.
    92. 610.11 Sizing Systems for Flushometer Tanks.
    93. 610.12 Sizing for Velocity.
    94. 610.13 Exceptions.
    95. 611.1 Application.
    96. 611.2 Air Gap Discharge.
    97. 611.3 Connection Tubing.
    98. 611.4 Sizing of Residential Softeners.
    99. 612.1 Installation.
    100. 613.1 The domestic water-heating equipment and distribu-
    101. 613.2 At least two pieces of hot-water-heating equipment shall
    102. 613.3 Instantaneous heaters are permitted for supplying hot
    103. 613.4 Water storage tanks shall be fabricated of corrosion-
    104. 613.5 Temperature control valves shall be provided to auto-
    105. 613.6 Hot-water distribution system serving patient care areas
    106. 613.7 At fixtures where water exceeding 125°F (52°C) is acces-
    107. 613.8 Sectionalizing valves shall be provided as required by S…
    108. 613.9 Hot water distribution shall include test ports and valved
    109. 614.1 Dialysis water feedlines shall be CPVC (chlorinated
    110. 614.2 All piping for multistation or central dialysis units sh…
    111. 614.3 All valves shall be located in accessible locations.
    112. 614.4 Piping and valves shall be identified according to their…
    113. 614.5 A means of preventing backwashing or flushing of the
    114. 614.6 A continuous audible alarm shall sound at the nurses’
    115. 614.7 Water treatment equipment and water used for dialysis
    116. 614.8 A diagram of all piping as installed shall be posted at …
    117. 615.1 Uses Not Permitted.
    118. 615.2 [OSHPD 1, 1R, 2, 3, 4 & 5]
    119. 615.3 [OSHPD 1, 1R, 2, 3, 4 & 5]
    120. 616.1 For new acute care hospital buildings submitted after
    121. 616.2 The emergency supply of water shall be provided at ade-
    122. 616.3 Storage tank connections and circulation shall be
  7. Chapter 7 — SANITARY DRAINAGE
  8. Chapter 8 — INDIRECT WASTES
  9. Chapter 9 — VENTS
  10. Chapter 10 — TRAPS AND INTERCEPTORS
  11. Chapter 11 — STORM DRAINAGE
  12. Chapter 12 — FUEL GAS PIPING
  13. Chapter 13 — HEALTH CARE FACILITIES AND MEDICAL GAS AND MEDICA…
  14. Chapter 14 — FIRESTOP PROTECTION
  15. Chapter 15 — ALTERNATE WATER SOURCES FOR NONPOTABLE APPLICATIONS
  16. Chapter 16 — NONPOTABLE RAINWATER CATCHMENT SYSTEMS
  17. Chapter 17 — REFERENCED STANDARDS
  18. Appendix A — RECOMMENDED RULES FOR SIZING THE WATER SUPPLY SYS…
  19. Appendix B — EXPLANATORY NOTES ON COMBINATION WASTE AND VENT S…
  20. Appendix C — ALTERNATE PLUMBING SYSTEMS
  21. Appendix D — SIZING STORM WATER DRAINAGE SYSTEMS
  22. Appendix E — MANUFACTURED/MOBILE HOME PARKS AND RECREATIONAL V…
  23. Appendix F — FIREFIGHTER BREATHING AIR REPLENISHMENT SYSTEMS
  24. Appendix G — SIZING OF VENTING SYSTEMS
  25. Appendix H — PRIVATE SEWAGE DISPOSAL SYSTEMS
  26. Appendix I — INSTALLATION STANDARDS
  27. Appendix J — COMBINATION OF INDOOR AND OUTDOOR COMBUSTION AND …
  28. Appendix K — POTABLE RAINWATER CATCHMENT SYSTEMS
  29. Appendix L — SUSTAINABLE PRACTICES
  30. Appendix M — PEAK WATER DEMAND CALCULATOR
  31. Appendix N — IMPACT OF WATER TEMPERATURE ON THE POTENTIAL FOR …
  32. Appendix O — NON-SEWERED SANITATION SYSTEMS
  33. Appendix P — PROFESSIONAL QUALIFICATIONS
  34. Appendix Q — INDOOR HORTICULTURAL FACILITIES
  35. Appendix R — TINY HOUSES
  36. Appendix S — ONSITE STORMWATER TREATMENT SYSTEMS

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