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Chapter 11 — STORM DRAINAGE

1101.6 Subsoil Drains. Subsoil drains shall be provided

California Plumbing Code (Title 24, Part 5) · 2019 edition · updated 2026-09-10 · California

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

around the perimeter of buildings having basements, cellars, crawl spaces, or floors below grade. Such subsoil drains shall be permitted to be positioned inside or outside of the footing, shall be of perforated or open-jointed approved drain tile or pipe, not less than 3 inches (80 mm) in diameter, and shall be laid in gravel, slag, crushed rock, approved 3 ⁄4 of an inch (19.1 mm) crushed, recycled glass aggregate, or other approved porous material with not less than 4 inches (102 mm) surrounding the pipe. Filter media shall be provided for exterior subsoil piping.

2019 CALIFORNIA PLUMBING CODE 211

STORM DRAINAGE any other purpose or distributed to any other persons or parti es.

Exception: [HCD 1 & HCD 2] Subsoil drains are manda- tory only when required by the Authority Having Jurisdiction due to geological conditions.

1101.6.1 Discharge. Subsoil drains shall be piped to a

1101.6.1 Discharge. Subsoil drains shall be piped to a storm drain, to an approved water course, to the front street curb or gutter, to an alley, or the discharge from the subsoil drains shall be conveyed to the alley by a concrete gutter. Where a continuously flowing spring or groundwater is encountered, subsoil drains shall be piped to a storm drain or an approved water course. 1101.6.2 Sump. Where it is not possible to convey the drainage by gravity, subsoil drains shall discharge to an accessible sump provided with an approved automatic electric pump. The sump shall be not less than 15 inches (381 mm) in diameter, 18 inches (457 mm) in depth, and provided with a fitted cover. The sump pump shall have an adequate capacity to discharge water coming into the sump as it accumulates to the required discharge point, and the capacity of the pump shall be not less than 15 gallons per minute (gpm) (0.95 L/s). The discharge piping from the sump pump shall be not less than 1 1 ⁄2 inches (40 mm) in diameter and have a union or other approved quick-disconnect assembly to make the pump accessible for servicing. 1101.6.3 Splash Blocks. For separate dwellings not serving continuously flowing springs or groundwater, the sump discharge pipe shall be permitted to discharge onto a concrete splash block with a minimum length of 24 inches (610 mm). This pipe shall be within 4 inches (102 mm) of the splash block and positioned to direct the flow parallel to the recessed line of the splash block. 1101.6.4 Backwater Valve. Subsoil drains subject to backflow where discharging into a storm drain shall be provided with a backwater valve in the drain line so located as to be accessible for inspection and maintenance. 1101.6.5 Open Area. Nothing in Section 1101.6 shall prevent drains that serve either subsoil drains or areaways of a detached building from discharging to a properly graded open area, provided that: (1) They do not serve continuously flowing springs or

groundwater.

(1) They do not serve continuously flowing springs or

groundwater. (2) The point of discharge is not less than 10 feet (3048

mm) from a property line.

(2) The point of discharge is not less than 10 feet (3048

mm) from a property line. (3) It is impracticable to discharge such drains to a

storm drain, to an approved water course, to the

m 2 ) in area, and shall be discharged in the manner provided for subsoil drains not serving continuously flowing springs or groundwater (see Section 1101.6.1). Areaways exceeding 100 square feet (9.29 m 2 ) shall not drain into subsoil drains. The drains for areaways exceeding 100 square feet (9.29 m 2 ) shall be sized in accordance with Table 1103.2.

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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. 1101.2 Where Required. Roofs, paved areas, yards, courts,
    2. 1101.3 Storm Water Drainage to Sanitary Sewer Pro-hibited. Sto…
    3. 1101.4 Material Uses. Pipe, tube, and fittings conveying
    4. 1101.5 Expansion Joints Required. Expansion joints or
    5. 1101.6 Subsoil Drains. Subsoil drains shall be provided
    6. 1101.9 Window Areaway Drains. Window areaways at a
    7. 1101.10 Filling Stations and Motor Vehicle WashingEstablishmen…
    8. 1101.11 Paved Areas. Where the occupant creates surface
    9. 1101.12 Roof Drainage. Roof drainage shall comply with
    10. 1101.7 Building Subdrains. Building subdrains located
    11. 1101.8 Areaway Drains. Open subsurface space adjacent
    12. 1101.13 Cleanouts. Cleanouts for building storm drains
    13. 1101.16 Leaders, Conductors, and Connections.
    14. 1101.14 Rainwater Sumps. Rainwater sumps serving
    15. 1101.15 Traps on Storm Drains and Leaders. Leaders
    16. 1102.2 Dome Strainers Required. Roof drains shall have
    17. 1102.3 Roof Drain Flashings. The connection between
    18. 1103.2 Size of Horizontal Storm Drains and Sewers.
    19. 1103.3 Size of Roof Gutters. The size of semi-circular
    20. 1103.4 Side Walls Draining onto a Roof. Where vertical walls p…
    21. 1104.0 Values for Continuous Flow.1104.1 General. Where there …
    22. 1105.0 Controlled-Flow Roof Drainage.1105.1 Application. Inste…
    23. 1105.2 Setback Roofs. Drains on setback roofs shall be
    24. 1106.2 Siphonic Roof Drainage Systems. The design of
    25. 1106.3 Siphonic Roof Drains. Siphonic roof drains shall
    26. 1107.2 Methods of Testing Storm Drainage Systems. Except for o…
  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 STANDARD FOR PEX TUBING SYSTEMS FOR …
  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

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