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Chapter 9 — VENTS

911.4 Relief Vent.

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.

A 2 inch (50 mm) relief vent shall be provided for circuit-vented horizontal branches receiving the discharge of four or more water closets and connecting to a drainage stack that receives the discharge of soil or waste from upper horizontal branches.

911.4.1 Connection and Installation. The relief vent shall connect to the horizontal branch drain between the stack and the most downstream fixture drain of the circuit vent. The relief vent shall be installed on the vertical to the horizontal branch. 911.4.2 Fixture Drain or Branch. The relief vent is permitted to be a fixture drain or fixture branch for a fixture located within the same branch interval as the circuit-vented horizontal branch. The discharge to a relief vent shall not exceed 4 fixture units.

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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
    Overview
    1. 901.2 Vents Required. Each plumbing fixture trap, except
    2. 901.3 Trap Seal Protection. The vent system shall be
    3. 902.2 Bars, Soda Fountains, and Counter. Traps serving sinks t…
    4. 903.0 Materials.903.1 Applicable Standards. Vent pipe and fitt…
    5. 903.2 Use of Copper or Copper Alloy Tubing. Copper
    6. 903.3 Changes in Direction. Changes in the direction of
    7. 904.0 Size of Vents.904.1 Size. The size of vent piping shall …
    8. 904.2 Length. Not more than one-third of the total permitted l…
    9. 905.2 Horizontal Drainage Pipe. Where vents connect to
    10. 905.3 Vent Pipe Rise. Unless prohibited by structural conditio…
    11. 905.4 Roof Termination. Vent pipes shall extend undiminished i…
    12. 905.5 Location of Opening. The vent pipe opening from
    13. 905.6 Common Vertical Pipe. Two fixtures shall be permitted to…
    14. 906.2 Clearance. Each vent shall terminate not less than
    15. 906.3 Use of Roof. Vent pipes shall be extended separately
    16. 906.4 Outdoor Installations. Vent pipes for outdoor
    17. 906.5 Joints. Joints at the roof around vent pipes shall be
    18. 906.6 Lead. (See Table 1701.1) Sheet lead shall comply
    19. 907.2 Yoke Vent. The yoke vent connection to the vent stack
    20. 908.0 Wet Venting.908.1 Vertical Wet Venting. Wet venting is l…
    21. 906.7 Frost or Snow Closure. Where frost or snow closure is li…
    22. 908.2 Horizontal Wet Venting for a Bathroom Group. A bathroom …
    23. 909.0 Special Venting for Island Fixtures.909.1 General. Traps…
    24. 910.2 Approval. Construction documents for each combination wa…
    25. 910.3 Vents. Each combination waste and vent system, as
    26. 910.4 Size. Each waste pipe and each trap in such a system
    27. 910.5 Vertical Waste Pipe. No vertical waste pipe shall be
    28. 910.6 Cleanouts. An accessible cleanout shall be installed
    29. 910.7 Fixtures. No water closet or urinal shall be installed
    30. 912.2 Minimum Requirements. An engineered vent system shall pr…
    31. 911.2 Vent Size and Connection. The circuit vent shall be
    32. 911.3 Slope and Size of Horizontal Branch. The slope
    33. 911.4 Relief Vent. A 2 inch (50 mm) relief vent shall be provi…
    34. 911.5 Additional Fixtures. Fixtures, other than the circuitven…
  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 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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