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Earlier editions: 20222019

Chapter 11 — STORM DRAINAGE

1101.12 Roof Drainage. Roof drainage shall comply with

California Plumbing Code (Title 24, Part 5) · 2025 edition · updated 2026-09-10 · California

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

Section 1101.12.1 and Section 1101.12.2.

1101.12.1 Primary Roof Drainage. Roof areas of a building shall be drained by roof drains or gutters. The location and sizing of drains and gutters shall be coordinated with the structural design and pitch of the roof. Unless otherwise required by the Authority Having Jurisdiction, roof drains, gutters, vertical conductors or leaders, and horizontal storm drains for primary drainage shall be sized based on a storm of 60 minutes duration and 100 year return period. Refer to Table D 101.1 (in Appendix D) for 100 years, 60-minute storms at various locations. 1101.12.2 Secondary Drainage. Secondary (emergency) roof drainage shall be provided by one of the methods specified in Section 1101.12.2.1 or Section 1101.12.2.2.

1101.12.2.1 Roof Scuppers or Open Side. Secondary roof drainage shall be provided by an opensided roof or scuppers where the roof perimeter construction extends above the roof in such a manner that water will be entrapped. An open-sided roof or scuppers shall be sized to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by Section 1101.12.1. Scupper openings shall be not less than 4 inches (102 mm) high and have a width equal to the circumference of the roof drain required for the area served, sized in accordance with Table 1103.1.

1101.12.2.2 Secondary Roof Drain. Secondary roof drains shall be provided. The secondary roof drains shall be located not less than 2 inches (51 mm) above the roof surface. The maximum height of the roof drains shall be a height to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by Section 1101.12.1. The secondary roof drains shall connect to a piping system in accordance with Section 1101.12.2.2.1 or Section 1101.12.2.2.2.

1101.12.2.2.1 Separate Piping System. The secondary roof drainage system shall be a

206 2025 CALIFORNIA PLUMBING CODE

STORM DRAINAGE

separate system of piping, independent of the primary roof drainage system. The discharge shall be above grade, in a location observable by the building occupants or maintenance personnel. Secondary roof drain systems shall be sized in accordance with Section 1101.12.1

based on the rainfall rate for which the primary system is sized. 1101.12.2.2.2 Combined System. The secondary roof drains shall connect to the vertical piping of the primary storm drainage conductor downstream of the last horizontal offset located below the roof. The primary storm drainage system shall connect to the building storm water that connects to an underground public storm sewer. The combined secondary and primary roof drain systems shall be sized in accordance with Section 1103.0 based on double the rain fall rate for the local area.

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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
    Overview
    1. 1101.1 Applicability. This chapter shall govern the materials,…
    2. 1101.2 Where Required. Roofs, paved areas, yards, courts,
    3. 1101.3 Storm Water Drainage to Sanitary Sewer Pro-
    4. 1101.4 Material Uses. Pipe, tube, and fittings conveying
    5. 1101.5 Expansion Joints Required. Expansion joints or
    6. 1101.6 Subsoil Drains. Subsoil drains shall be provided
    7. 1101.7 Building Subdrains. Building subdrains located
    8. 1101.8 Areaway Drains. Open subsurface space adjacent
    9. 1101.9 Window Areaway Drains. Window areaways at a
    10. 1101.10 Filling Stations and Motor Vehicle Washing
    11. 1101.11 Paved Areas. Where the occupant creates surface
    12. 1101.12 Roof Drainage. Roof drainage shall comply with
    13. 1101.13 Cleanouts. Cleanouts for building storm drains
    14. 1101.14 Rainwater Sumps. Rainwater sumps serving
    15. 1101.15 Traps on Storm Drains and Leaders. Leaders
    16. 1101.16 Leaders, Conductors, and Connections.
    17. 1102.1 Applications. Roof drains shall be constructed of
    18. 1102.2 Dome Strainers Required. Roof drains shall have
    19. 1102.3 Roof Drain Flashings. The connection between
    20. 1103.1 Vertical Conductors and Leaders. Vertical conductors an…
    21. 1103.2 Size of Horizontal Storm Drains and Sewers.
    22. 1103.3 Size of Roof Gutters. The size of semi-circular
    23. 1103.4 Side Walls Draining onto a Roof. Where vertical walls p…
    24. 1104.1 General. Where there is a continuous or semi-continuous…
    25. 1105.1 Application. Instead of sizing the storm drainage
    26. 1105.2 Setback Roofs. Drains on setback roofs shall be
    27. 1106.1 General. The design and sizing of a storm drainage
    28. 1106.2 Siphonic Roof Drainage Systems. The design of
    29. 1106.3 Siphonic Roof Drains. Siphonic roof drains shall
    30. 1107.1 Testing Required. New building storm drainage
    31. 1107.2 Methods of Testing Storm Drainage Systems.
  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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