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Chapter 15 — ALTERNATE WATER SOURCES FOR NONPOTABLE APPLICATIONS

1503.2 System Requirements.

California Plumbing Code (Title 24, Part 5) · 2022 edition · updated 2026-09-10 · California

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

Gray water shall be permitted to be diverted away from a sewer or private sewage disposal system, and discharge to a subsurface irrigation or subsoil irrigation system , or disposal field . The gray water shall be permitted to discharge to a mulch basin for residen- tial occupancies . Gray water shall not be used to irrigate root crops or food crops intended for human consumption that comes in contact with soil.

1503.2.1 Surge Capacity. Gray water systems shall be designed to have the capacity to accommodate peak

ALTERNATE WATER SOURCES FOR NONPOTABLE APPLICATIONS

flow rates and distribute the total amount of estimated gray water on a daily basis to a subsurface irrigation field, subsoil irrigation field , disposal field, or mulch basin without surfacing, ponding, or runoff. A surge tank is required for systems that are unable to accommodate peak flow rates and distribute the total amount of gray water by gravity drainage. The water discharge for gray water systems shall be determined in accordance with Section 1503.8.1 or Section 1503.8.2. Exception: It is not the intent of this section to require that all gray water must be handled by an irrigation field or disposal field. It is acceptable for excess gray water to be diverted to the building sewer through a diverter valve or overflow drain as permitted in this chapter. 1503.2.2 Diversion. The gray water system shall connect to the sanitary drainage system downstream of fixture traps and vent connections through an approved diverter valve. The diverter valve shall be installed in a readily accessible location and clearly indicate the direction of flow. Exception: [HCD 1] A clothes washer system in com- pliance with Section 1503.1.1. 1503.2.3 Backwater Valves. Gray water drains subject to backflow shall be provided with a backwater valve at the point of connection to the building sewer system, so located as to be accessible for inspection and maintenance. 1503.2.4 Rainwater Diversion Valves. Rainwater diversion valves ranging from 6 inches (150 mm) to 12 inches (300 mm) in diameter shall comply with IAPMO IGC 352. Valves shall be accessible and include a filter located upstream of the valve when required.

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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
  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
    Overview
    1. 1501.1 Applicability [BSC-CG, DWR & HCD 1] . The
    2. 1501.2 System Design. Alternate water source systems
    3. 1501.3 Permit [BSC-CG, HCD 1, DWR] . It shall be unlawful for …
    4. 1501.4 Component Identification. System components
    5. 1501.5 Maintenance and Inspection [BSC-CG, HCD
    6. 1501.6 Operation and Maintenance Manual [BSC-CG,
    7. 1501.7 Minimum Water Quality Requirements [BSC-
    8. 1501.8 Material Compatibility. Alternate water source systems …
    9. 1501.9 Signage [BSC-CG, HCD 1, HCD 2, HCD 1-AC].
    10. 1501.10 System Controls. Controls for pumps, valves, and
    11. 1502.1 General. Alternate water source systems shall be
    12. 1502.2 Supply System Inspection and Test. Alternate
    13. 1502.3 Cross-Connection Inspection and Testing. An
    14. 1502.4 Separation Requirements. Underground alternate water so…
    15. 1502.5 Abandonment. Alternate water source systems that
    16. 1502.6 Sizing. Unless otherwise provided for in this chapter, …
    17. 1503.1 General. The provisions of this section shall apply
    18. 1503.2 System Requirements. Gray water shall be permitted to b…
    19. 1503.3 Connections to Potable and Reclaimed (Recy-
    20. 1503.4 Location. No gray water system or part thereof shall
    21. 1503.5 Plot Plan Submission. No permit for a gray water
    22. 1503.6 Prohibited Location. Where there is insufficient
    23. 1503.7 Drawings and Specifications. The Authority
    24. 1503.8 Procedure for Estimating Gray Water Dis-
    25. 1503.9 Gray Water System Components. Gray water
    26. 1504.1 General. Irrigation or disposal fields shall be permitt…
    27. 1504.3 Determination of Maximum Absorption
    28. 1504.4 Groundwater Level. No excavation for an irrigation fiel…
    29. 1504.2 Required Area of Subsurface Irrigation
    30. 1504.5 Irrigation, Disposal Field and Mulch Basin Con-
    31. 1504.6 Reserved.
    32. 1504.7 Reserved .
    33. 1504.8 Gray Water System Color and Marking Infor-
    34. 1504.9 Other Collection and Distribution Systems.
    35. 1504.10 Testing. Building drains and vents for gray water
    36. 1504.11 Maintenance. Gray water systems and components shall b…
    37. 1505.1 General. The provisions of Section 1505.0 through
    38. 1505.2 Permit. It shall be unlawful for a person to construct,
    39. 1505.3 System Changes. No changes or connections shall
    40. 1505.4 Connections to Potable or Recycled Water
    41. 1505.5 Initial Cross-Connection Test. A cross-connection test …
    42. 1505.6 Recycled Water Supply System Materials.
    43. 1505.7 Recycled Water Supply System Color and
    44. 1505.8 Valves. Valves, except fixture supply control valves,
    45. 1505.9 Hose Bibbs. Hose bibbs shall not be allowed on
    46. 1505.10 Required Appurtenances. The recycled water
    47. 1505.11 Pipe Separation in Trenches . Reclaimed (recycled) wat…
    48. 1505.12 Signage . Signs in rooms and water closet tanks in
    49. 1505.13 Inspection and Testing. Recycled water supply
    50. 1505.14 Minimum Water Quality Requirements for
    51. 1505.15 Maintenance and Inspection. Recycled water
    52. 1506.1 General. The provisions of this section shall apply
    53. 1506.2 Plumbing Plan Submission. No permit for an
    54. 1506.3 System Changes. No changes or connections shall
    55. 1506.4 Connections to Potable or Recycled Water
    56. 1506.5 Initial Cross-Connection Test. A cross-connection test …
    57. 1506.6 On-Site Treated Nonpotable Gray Water Sys-
    58. 1506.7 On-Site Treated Nonpotable Gray Water
    59. 1506.8 On-Site Treated Nonpotable Gray Water Sys-
    60. 1506.9 Design and Installation. The design and installation of…
    61. 1506.10 Valves. Valves, except fixture supply control
    62. 1506.11 Signs. Signs in buildings using on-site treated nonpot…
    63. 1506.12 Inspection and Testing. On-site treated nonpotable gra…
  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 …

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