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Chapter 12 — HYDRONICS

1216.4 Automatic Air Vents. Steam automatic air vents

California Mechanical Code (Title 24, Part 4) · 2022 edition · updated 2026-09-10 · California

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

shall be installed to eliminate air pressure in heat-distribution

HYDRONICS

units on gravity steam piping systems. Air vents shall not be used on a vacuum system.

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▸Contents — California Mechanical Code (Title 24, Part 4)
California Mechanical Code (Title 24, Part 4)
  1. Chapter 1 — GENERAL CODE PROVISIONS
  2. Chapter 2 — DEFINITIONS
  3. Chapter 3 — GENERAL REGULATIONS
  4. Chapter 4 — VENTILATION AIR
  5. Chapter 5 — EXHAUST SYSTEMS
  6. Chapter 6 — DUCT SYSTEMS
  7. Chapter 7 — COMBUSTION AIR
  8. Chapter 8 — CHIMNEYS AND VENTS
  9. Chapter 9 — INSTALLATION OF SPECIFIC APPLIANCES
  10. Chapter 10 — BOILERS AND PRESSURE VESSELS
  11. Chapter 11 — REFRIGERATION
  12. ▸Chapter 12 — HYDRONICS
    Overview
    1. 1201.1 Applicability. This chapter shall apply to hydronic
    2. 1201.2 Insulation. Surfaces within reach of building occupants…
    3. 1201.3 Water Hammer. The piping system shall be
    4. 1201.4 Terminal Units. Terminal units, valves, and flow
    5. 1201.5 Return-Water Low-Temperature Protection.
    6. 1202.1 Prohibited Sources. Hydronic systems or parts
    7. 1202.2 Chemical Injection. Where systems include an
    8. 1202.3 Compatibility. Fluids used in hydronic systems
    9. 1203.1 Heat Source. The heat source shall be sized to the
    10. 1203.2 Dual Purpose Water Heater. Water heaters utilized for c…
    11. 1203.3 Tankless Water Heaters. Tankless water heaters
    12. 1204.1 General. In buildings where potable water and nonpotabl…
    13. 1204.2 Color and Information. Each system shall be identified …
    14. 1204.3 Potable Water. Potable water systems shall be identifie…
    15. 1204.4 Nonpotable Water. Nonpotable water systems
    16. 1204.5 Location of Piping Identification. The background
    17. 1204.6 Flow Directions. Flow directions shall be indicated
    18. 1205.1 Operating Instructions. Operating and maintenance
    19. 1205.2 Pressure Testing. System piping and components
    20. 1205.3 Flushing. Heating and cooling sources, system piping an…
    21. 1206.1 General. Each closed hydronic system shall be protected…
    22. 1206.2 Discharge Piping. The discharge piping serving a
    23. 1207.1 General. Heating appliances, equipment, safety and
    24. 1207.2 Boilers. Boilers and their control systems shall comply…
    25. 1207.3 Dual-Purpose Water Heaters. Water heaters used
    26. 1207.4 Solar Heat Collector Systems. Solar water heating syste…
    27. 1208.1 General. Circulators and pumps shall be selected
    28. 1208.2 Mounting. The circulator or pump shall be installed
    29. 1208.3 Sizing. The selection and sizing of a circulator or
    30. 1209.1 General. An expansion tank shall be installed in each
    31. 1209.2 Installation. Expansion tanks shall be accessible for
    32. 1209.3 Open-Type Expansion Tanks. Open type expansion tanks sh…
    33. 1209.4 Closed-Type Tanks. Closed-type expansion tanks
    34. 1209.5 Sizing. Expansion tanks shall be sized to accept the
    35. 1210.1 Piping, Tubing, and Fittings. Hydronic pipe and
    36. 1210.2 Expansion and Contraction. Pipe and tubing shall
    37. 1210.3 Hangers and Supports. Pipe and tubing shall be
    38. 1210.4 Oxygen Diffusion Corrosion. PEX and PE-RT tubing in clo…
    39. 1211.1 General. Joints and connections shall be of an
    40. 1211.2 Chlorinated Polyvinyl Chloride (CPVC) Pipe.
    41. 1211.3 CPVC/AL/CPVC Plastic Pipe and Joints. Joints
    42. 1211.4 Copper or Copper Alloy Pipe and Tubing.
    43. 1211.5 Cross-Linked Polyethylene (PEX) Pipe. Joints
    44. 1211.6 Cross-Linked Polyethylene/Aluminum/Cross-
    45. 1211.7 Ductile Iron Pipe. Joints between ductile iron pipe
    46. 1211.8 Polyethylene (PE) Plastic Pipe/Tubing. Joints
    47. 1211.9 Polyethylene/Aluminum/Polyethylene (PE-AL-
    48. 1211.10 Polyethylene of Raised Temperature (PE-RT).
    49. 1211.11 Polypropylene (PP) Pipe. Joints between
    50. 1211.12 Polyvinyl Chloride (PVC) Pipe. Joints between
    51. 1211.13 Steel Pipe and Tubing. Joints between steel pipe
    52. 1211.14 Joints Between Various Materials. Joints
    53. 1212.1 General. Valves shall be rated for the operating temper…
    54. 1212.2 Where Required. Valves shall be installed in
    55. 1212.3 Heat Exchanger. Isolation valves shall be installed
    56. 1212.4 Pressure Vessels. Isolation valves shall be installed
    57. 1212.5 Pressure Reducing Valves. Isolation valves shall
    58. 1212.6 Equipment, Components, and Appliances. Serviceable equi…
    59. 1212.7 Expansion Tank. Isolation valves shall be installed
    60. 1212.8 Flow Balancing Valves. Where flow balancing
    61. 1212.9 Mixing or Temperature Control Valves. Where
    62. 1212.10 Thermosiphoning. An approved type check valve
    63. 1212.11 Air Removal Device or Air Vents. Isolation valves
    64. 1213.1 Water Temperature Controls. A heat source or system of …
    65. 1213.2 Operating Steam Controls. A steam heat source or
    66. 1213.3 Occupied Spaces. A temperature-sensing device
    67. 1213.4 Simultaneous Operation. Radiant heating and cooling sys…
    68. 1213.5 Temperature Reading. A temperature gauge or
    69. 1214.1 Balancing. A means for balancing distribution
    70. 1214.2 Low-Water Control. Direct-fired heat sources
    71. 1214.3 Flow-Sensing Devices. A direct-fired heat source,
    72. 1214.4 Automatic Makeup Fluid. Where an automatic
    73. 1214.5 Differential Pressure Regulation. Provisions
    74. 1214.6 Air-Removal Device. Provision shall be made for
    75. 1214.7 Air-Separation Device. To assist with the removal
    76. 1214.8 Secondary Loops. Secondary loops that are isolated from…
    77. 1215.1 General. Based on the system design, the heat-distribut…
    78. 1215.2 Installation. Heat-distribution units shall be
    79. 1215.3 Freeze Protection. Hydronic systems and components shal…
    80. 1215.4 Balancing. System loops shall be installed so that
    81. 1215.5 Heat Transfer Fluid. The ignitable flash point of
    82. 1216.1 Steam Traps. For other than one-pipe steam systems, eac…
    83. 1216.2 Sloping for Two-Pipe System. Two-pipe steam
    84. 1216.3 Sloping for One-Pipe System. One-pipe steam
    85. 1216.4 Automatic Air Vents. Steam automatic air vents
    86. 1216.5 Condensate Flow. System piping shall be installed
    87. 1216.6 Steam-Distribution Piping. Where multi-row elements are…
    88. 1217.1 Installation. Radiant heating and cooling systems
    89. 1217.2 Radiant Under-Floor Heating. Floor finished surface tem…
    90. 1217.3 Radiant Cooling Systems. Radiant cooling systems shall …
    91. 1217.4 Tube Placement. Hydronic radiant system tubing
    92. 1217.6 Joist Systems and Subfloors. Where tubing is
    93. 1217.7 Wall and Ceiling Panels. Where piping is installed
    94. 1217.5 Poured Floor Structural Concrete Slab Sys-
    95. 1219.1 General. Domestic hot-water heat exchangers,
    96. 1220.1 Use of Chemical Additives and Corrosive Flu-
    97. 1220.2 Types of Tube Fasteners. Tubing that is embedded within…
    98. 1220.3 Spacing of Tube Fasteners. The maximum spacing between …
    99. 1217.8 Radiant Heating and Cooling Panels. Radiant
    100. 1218.1 General. Systems utilizing heat exchangers shall
    101. 1220.4 Snow and Ice Melt Controls. An automatic thermostatical…
    102. 1220.5 Hydronic Makeup Air Units. Hydronic makeup
    103. 1221.1 General. Piping, fittings, and connections shall be
    104. 1221.2 Embedded Piping Materials and Joints. Piping embedded i…
    105. 1221.3 Pressure Testing. Piping to be embedded in concrete sha…
    106. 1221.4 System Drainage. Hydronic piping systems shall
    107. 1221.5 Condensate Drainage. Condensate drains from
    108. 1221.6 Clearance to Combustibles. Hydronic piping
  13. Chapter 13 — FUEL GAS PIPING
  14. Chapter 14 — PROCESS PIPING
  15. Chapter 15 — SOLAR ENERGY SYSTEMS
  16. Chapter 16 — STATIONARY POWER PLANTS
  17. Chapter 17 — REFERENCED STANDARDS
  18. Appendix A — RESIDENTIAL PLAN EXAMINER REVIEW FORM FOR HVAC SY…
  19. Appendix B — PROCEDURES TO BE FOLLOWED TO PLACE GAS EQUIPMENT …
  20. Appendix C — INSTALLATION AND TESTING OF OIL (LIQUID) FUEL-FIR…
  21. Appendix D — FUEL SUPPLY: MANUFACTURED/MOBILE HOME PARKS AND R…
  22. Appendix E — SUSTAINABLE PRACTICES
  23. Appendix F — GEOTHERMAL ENERGY SYSTEMS
  24. Appendix G — SIZING OF VENTING SYSTEMS AND OUTDOOR COMBUSTION …
  25. Appendix H — EXAMPLE CALCULATION OF OUTDOOR AIR RATE

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