CMC · California Mechanical Code
What workmanship and installation practices are required for mechanical systems?
Mechanical systems in California must be designed and installed to recognized engineering practices, cannot have defects hidden with sealants or cosmetic fixes, and must be installed per the Code, applicable standards and the equipment manufacturer’s instructions — all work must match construction documents approved by the local authority (see §§ 309.1–309.3).
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
Mechanical systems must be designed and built to accepted engineering practices and installed so the finished work actually achieves the safety and performance the Code intends (see § 309.1) . It is unlawful to conceal cracks, holes, leaks or other imperfections by welding, brazing, soldering or by using paint, wax, tar, solvent cement or other leak‑sealing or repair agents (see § 309.2) . Installations must follow the CMC, applicable standards, and the manufacturer’s installation instructions, and must conform to construction documents approved by the Authority Having Jurisdiction (see § 309.3) .
The single most important rule: mechanical work must be engineered and installed to recognized practices and standards — you may not hide defects with temporary patches; follow the Code, standards and manufacturer instructions and submit approved construction documents.
Requirements in detail
1) Design & workmanship standard: accepted engineering practices
- What it means: Design, construction, and workmanship must comply with professional/industry standards (drawings, sizing, support, materials, testing) so the installation produces the safety and performance the Code intends. See § 309.1.
- Practical implications:
- Use recognized calculation methods and referenced standards for sizing and load calculations.
- Use listed materials and devices where the Code requires listing and marking. (See related materials provisions in the CMC for marking/standards.)
2) Prohibition on concealing imperfections
- Core rule: It is prohibited to conceal cracks, holes, or other imperfections by welding, brazing, soldering, or by applying paint, wax, tar, solvent cement or other leak‑sealing or repair agents — repairs must be proper, not cosmetic. See § 309.2.
- Practical implications:
- Stop using “quick‑fix” sealants to hide pinhole leaks in piping, ductwork, gas fittings or boilers; replace or properly repair the defective component.
- Do not cover poor welds or brazes with coatings to pass inspection; the underlying fault must be corrected.
3) Installation practices — follow code, standards, manufacturer, approved documents
- Core rule: Mechanical systems must be installed in accordance with the CMC, applicable referenced standards, the manufacturer’s installation instructions, and construction documents approved by the Authority Having Jurisdiction (AHJ). See § 309.3.
- Practical implications:
- Follow manufacturer clearances, mounting, piping and wiring instructions (nameplate and manual) as part of compliance. See appliance labeling/clearance requirements, which are tied to manufacturer instructions.
- Submit construction documents/drawings and obtain AHJ approval before concealed work proceeds.
- Coordinate referenced standards (product listings, NFPA, SMACNA, ASHRAE etc.) required elsewhere in the Code.
Quick decision table (decision‑relevant dimensions / values)
| Practice / situation | What the installer must do | Code Reference |
|---|---|---|
| Design, calculations, supports, materials quality | Use accepted engineering practices and recognized standards so the work secures the intended results | § 309.1 |
| Repair of cracks/holes/leaks | Do not conceal with welding, brazing, soldering or coatings/plugging agents; perform proper repair or replacement | § 309.2 |
| Following manufacturer instructions | Install exactly per the manufacturer’s installation instructions (clearances, wiring, condensate handling, driers, etc.) | § 309.3 |
| Documentation & approvals | Installations must match construction documents approved by the AHJ; do not conceal work before inspection | § 309.3 |
Exceptions & special cases
- The CMC text for § 309.1–309.3 as retrieved does not list explicit exceptions to these workmanship and installation requirements. I cannot invent exceptions; any permitted deviations (for example, alternate materials or methods) must be authorized by the AHJ or handled under Code sections that address alternates or existing buildings. See the Code for alternate‑method provisions elsewhere.
- Where the AHJ has discretionary authority (existing buildings or approved alternates), follow the AHJ’s written approval and conditions (see related Code sections addressing alternates/approval processes) .
Common mistakes
- Patching a leak with sealant or paint so it is not visible on inspection — that violates § 309.2 (don’t conceal imperfections) .
- Ignoring or modifying manufacturer installation instructions (clearances, wiring temperature ratings, drier requirements) — installations must follow manufacturer instructions per § 309.3 .
- Installing components that are not listed or marked per their referenced standard and expecting approval — materials are required to meet standards and be marked where the Code requires (related materials/standards provisions) .
- Covering or concealing work before approval/inspection — construction documents approved by the AHJ are required and the AHJ may require visibility for inspection per other codes (see inspection provisions).
Worked example — gas furnace replacement (concrete scenario)
Scenario: Replace a residential gas furnace in a utility closet.
Design and documentation:
- Prepare construction documents showing furnace model, location, clearances, vent routing, gas and vent piping, access panels and service clearances; submit to AHJ and obtain approval. This satisfies the requirement that mechanical systems conform to construction documents approved by the AHJ per § 309.3.
Follow manufacturer instructions:
- Confirm the furnace nameplate/manual clearances (e.g., X inches from combustibles — consult the nameplate). Install per the manufacturer's instructions for vent connector slope, connector type, combustion air and clearances. Manufacturer instructions form part of the required installation compliance under § 309.3.
Do proper repairs — do not conceal:
- If you discover a cracked flue connector or pinhole in a gas piping fitting during installation, replace the defective component rather than braze over it and paint — § 309.2 forbids concealing cracks/holes with welding, brazing, soldering, paint, tar, solvent cement or similar leak‑sealing agents.
Workmanship and accepted practices:
- Size the vent, gas piping and combustion air openings using accepted engineering practices and referenced standards (e.g., sizing tables and referenced NFPA/IAPMO procedures). That satisfies § 309.1 requirement for accepted engineering practices.
Inspection:
- Leave work visible for AHJ inspection until authorized to cover; the installation must match approved construction documents per § 309.3.
Related provisions (CMC sections to consult)
- § 302.1 — Materials, listing, marking and standards for equipment and devices used in mechanical systems.
- § 304.1 — Accessibility for service (clearance and access requirements for serviceable appliances).
- § 307.0 / § 307.1–307.4 — Labeling and nameplate requirements (appliance nameplates and manufacturer‑provided installation information, including required clearances).
- § 308.1 — Location limitations (piping/equipment location that may interfere with normal use).
- § 310.1 — Condensate disposal and sizing requirements (where condensate collection/drainage is part of the appliance installation).
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 307.4 High relevance — show source text
(11)Required clearances from combustible surfaces on which or adjacent to which it is permitted to be mounted.
An appliance shall be accompanied by clear and complete installation instructions, including required clearances from combustible other than mounting or adjacent surfaces, and temperature rating of field-installed wiring connections exceeding 140°F (60°C). 307.4 Absorption Units. Absorption units shall bear a permanent and legible factory-applied nameplate on which shall
appear:
(1) The name or trademark of the manufacturer.
(2) The model number or equivalent.
(3) The serial number.
(4) The amount of refrigerant.
(5) The refrigerant designation.
(6) Hourly rating in Btu/h (kW).
(7) The type of fuel approved for use with the unit.
(8) Cooling capacity Btu/h (kW).
(9) Required clearances from combustible surfaces on which or adjacent to which it is permitted to be mounted.
(10)The symbol of an approved agency certifying compliance of the equipment with recognized standards.
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GENERAL REGULATIONS
308.0 Improper Location.
308.1 General. Piping or equipment shall not be so located as to interfere with the normal use thereof or with the normal operation and use of windows, doors, or other required facilities.
309.0 Workmanship.
309.1 Engineering Practices. Design, construction, and workmanship shall comply with accepted engineering practices and shall be of such character as to secure the results sought to be obtained by this code.
309.2 Concealing Imperfections. It shall be unlawful to conceal cracks, holes, or other imperfections in materials by welding, brazing, or soldering, by using therein or thereon paint, wax, tar, solvent cement, other leak-sealing or repair agent.
309.3 Installation Practices. Mechanical systems shall be installed in a manner that is in accordance with this code, applicable standards, and the manufacturer’s installation instructions. All mechanical systems shall be in accordance with construction documents approved by the Authority Having Jurisdiction.
310.0 Condensate Wastes and Control.
310.1 Condensate Disposal. Condensate from air washers, air-cooling coils, condensing appliances, and the overflow from evaporative coolers and similar water-supplied equipment or similar air-conditioning equipment shall be collected and discharged to an approved plumbing fixture or disposal area. Where discharged into the drainage system, equipment shall drain by means of an indirect waste pipe. The waste pipe shall have a slope of not less than [1] ⁄ 8 inch per foot (10.4 mm/m) or 1 percent slope and shall be of approved corrosion-resistant material not smaller than the outlet size in
accordance with Section 310.3 or Section 310.4 for air-cooling coils or condensing appliances, respectively. Condensate or wastewater shall not drain over a public way.
CMC § 309.0 High relevance — show source text
309.0 Workmanship.
309.1 Engineering Practices. Design, construction, and workmanship shall comply with accepted engineering practices and shall be of such character as to secure the results sought to be obtained by this code.
309.2 Concealing Imperfections. It shall be unlawful to conceal cracks, holes, or other imperfections in materials by welding, brazing, or soldering, by using therein or thereon paint, wax, tar, solvent cement, other leak-sealing or repair agent.
309.3 Installation Practices. Mechanical systems shall be installed in a manner that is in accordance with this code, applicable standards, and the manufacturer’s installation instructions. All mechanical systems shall be in accordance with construction documents approved by the Authority Having Jurisdiction.
310.0 Condensate Wastes and Control.
310.1 Condensate Disposal. Condensate from air washers, air-cooling coils, condensing appliances, and the overflow from evaporative coolers and similar water-supplied equipment or similar air-conditioning equipment shall be collected and discharged to an approved plumbing fixture or disposal area. Where discharged into the drainage system, equipment shall drain by means of an indirect waste pipe. The waste pipe shall have a slope of not less than [1] ⁄ 8 inch per foot (10.4 mm/m) or 1 percent slope and shall be of approved corrosion-resistant material not smaller than the outlet size in
accordance with Section 310.3 or Section 310.4 for air-cooling coils or condensing appliances, respectively. Condensate or wastewater shall not drain over a public way.
310.1.1 Condensate Pumps. Where approved by the Authority Having Jurisdiction, condensate pumps shall be installed in accordance with the manufacturer’s installation instructions. Pump discharge shall rise vertically to a point where it is possible to connect to a gravity condensate drain and discharged to an approved disposal point. Each condensing unit shall be provided with a separate sump and interlocked with the equipment to prevent the equipment from operating during a failure. Separate pumps shall be permitted to connect to a single gravity indirect waste where equipped with check valves and approved by the Authority Having Jurisdiction.
310.2 Condensate Control. Where any equipment or appliance is installed in a space where damage is capable of resulting from condensate overflow, a drain line shall be provided and shall be drained in accordance with Section 310.1. An additional protection method for condensate overflow shall be provided in accordance with one of the following:
(1) A water level detecting device that will shut off the equipment or appliance in the event the primary drain is
EQUIPMENT CAPACITY IN
TONS OF REFRIGERATIONMINIMUM CONDENSATE
PIPE DIAMETER
(inches)
Up to 203⁄4
21 – 401
41 – 9011⁄4
91 – 12511⁄2
126 – 2502 For SI units: 1 ton of refrigeration = 3.52 kW, 1 inch = 25 mm
CMC § 1404.5 High relevance — show source text
1404.5 Insulation and Coverings . . . . . . .305
1404.6 Sleeves . . . . . . . . . . . . . . . . . . . . .305
1405.0 Noncombustible Piping Installations . . . . . . . . . . . . . . . . . .305
1405.1 General Requirements . . . . . . . . .305
1405.2 Fire-Resistance Rating . . . . . . . . .305
1405.3 Firestop Systems . . . . . . . . . . . . .305
1405.4 Connections . . . . . . . . . . . . . . . . .305
1405.5 Unshielded Couplings . . . . . . . . . .306
1405.6 Sleeves . . . . . . . . . . . . . . . . . . . . .306
1405.7 Insulation and Coverings . . . . . . .306
1406.0 Required Inspection . . . . . . . . . . .306
1406.1 General . . . . . . . . . . . . . . . . . . . . .306
1406.2 Examination . . . . . . . . . . . . . . . . .306
1406.3 Penetrations . . . . . . . . . . . . . . . . .306
1406.4 Field Installations . . . . . . . . . . . . .306
CHAPTER 15 ALTERNATE WATER SOURCES
FOR NONPOTABLE
APPLICATIONS . . . . . . . . . . . . . .307
1501.0 General . . . . . . . . . . . . . . . . . . . . .309
1501.1 Applicability . . . . . . . . . . . . . . . . . .309
1501.2 System Design . . . . . . . . . . . . . . .309
1501.3 Permit . . . . . . . . . . . . . . . . . . . . . .309
1501.4 Component Identification . . . . . . .309
1501.5 Maintenance and Inspection . . . .309
1501.6 Operation and Maintenance Manual . . . . . . . . . . . . . . . . . . . . .309
1501.7 Minimum Water Quality Requirements . . . . . . . . . . . . . . . .309
Table 1501.5 Recommended Minimum Alternate Water Source Testing, Inspection, and Maintenance Frequency . . . . . . . . . . . . . . . . . . .310
1501.8 Material Compatibility . . . . . . . . . .310
1501.9 Signage . . . . . . . . . . . . . . . . . . . .310
1501.10 System Controls . . . . . . . . . . . . . .310
1502.0 Inspection and Testing . . . . . . . . .310
1502.1 General . . . . . . . . . . . . . . . . . . . . .310
1502.2 Supply System Inspection and Test . . . . . . . . . . . . . . . . . . . .310
1502.3 Cross-Connection
CMC § 305.6 High relevance — show source text
305.6 Outdoor Locations . . . . . . . . . . . . . 55
306.0 Automatic Control Devices . . . . . . . 55
306.1 General. . . . . . . . . . . . . . . . . . . . . . 55
306.2 Building Automation Systems . . . . 56
2025 CALIFORNIA MECHANICAL CODE
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TABLE OF CONTENTS
307.0 Labeling . . . . . . . . . . . . . . . . . . . . . 56
307.1 Fuel-Burning Appliances . . . . . . . . 56
307.2 Electric Heating Appliances . . . . . . 56
307.3 Heat Pump and Electric Cooling Appliances . . . . . . . . . . . . . . . . . . . 56
307.4 Absorption Units . . . . . . . . . . . . . . . 56
308.0 Improper Location. . . . . . . . . . . . . . 57
308.1 General. . . . . . . . . . . . . . . . . . . . . . 57
309.0 Workmanship . . . . . . . . . . . . . . . . . 57
309.1 Engineering Practices. . . . . . . . . . . 57
309.2 Concealing Imperfections . . . . . . . . 57
309.3 Installation Practices. . . . . . . . . . . . 57
310.0 Condensate Wastes and Control . . 57
310.1 Condensate Disposal . . . . . . . . . . . 57
310.2 Condensate Control . . . . . . . . . . . . 57
310.3 Condensate Waste Pipe Material and Sizing. . . . . . . . . . . . . . . . . . . . 57
Table 310.3 Minimum Condensate Pipe Size. . . 57
310.4 Appliance Condensate Drains . . . . 58
310.5 Point of Discharge . . . . . . . . . . . . . 58
310.6 Condensate Waste from
Air-Conditioning Coils . . . . . . . . . . . 58
310.7 Female Plastic Connections . . . . . . 58
311.0 Heating or Cooling Air System . . . . 58
311.1 Source . . . . . . . . . . . . . . . . . . . . . . 58
311.2 Air Filters . . . . . . . . . . . . . . . . . . . . 58
311.3 Prohibited Sources . . . . . . . . . . . . . 58
311.4 Return-Air Limitations . . . . . . . . . . . 58
311.5 California Energy Code Requirements for Residential
Air Filtration . . . . . . . . . . . . . . . . . . 59
312.0 Plumbing Connections . . . . . . . . . . 59
312.1 General. . . . . . . . . . . . . . . . . . . . . . 59
CMC § 1501.0 High relevance — show source text
1501.0 General . . . . . . . . . . . . . . . . . . . . .309
1501.1 Applicability . . . . . . . . . . . . . . . . . .309
1501.2 System Design . . . . . . . . . . . . . . .309
1501.3 Permit . . . . . . . . . . . . . . . . . . . . . .309
1501.4 Component Identification . . . . . . .309
1501.5 Maintenance and Inspection . . . .309
1501.6 Operation and Maintenance Manual . . . . . . . . . . . . . . . . . . . . .309
1501.7 Minimum Water Quality Requirements . . . . . . . . . . . . . . . .309
Table 1501.5 Recommended Minimum Alternate Water Source Testing, Inspection, and Maintenance Frequency . . . . . . . . . . . . . . . . . . .310
1501.8 Material Compatibility . . . . . . . . . .310
1501.9 Signage . . . . . . . . . . . . . . . . . . . .310
1501.10 System Controls . . . . . . . . . . . . . .310
1502.0 Inspection and Testing . . . . . . . . .310
1502.1 General . . . . . . . . . . . . . . . . . . . . .310
1502.2 Supply System Inspection and Test . . . . . . . . . . . . . . . . . . . .310
1502.3 Cross-Connection
Inspection and Testing . . . . . . . . .310
1502.4 Separation Requirements . . . . . . .311
1502.5 Abandonment . . . . . . . . . . . . . . . .311
1502.6 Sizing . . . . . . . . . . . . . . . . . . . . . .312
1503.0 Gray Water Systems . . . . . . . . . .312
1503.1 General . . . . . . . . . . . . . . . . . . . . .312
1503.2 System Requirements . . . . . . . . .313
1503.3 Connections to Potable and
Reclaimed (Recycled) Water Systems . . . . . . . . . . . . . . . . . . . . .313
1503.4 Location . . . . . . . . . . . . . . . . . . . .313
1503.5 Plot Plan Submission . . . . . . . . . .313
1503.6 Prohibited Location . . . . . . . . . . . .313
Table 1503.4 Location of Gray Water System . . .314
1503.7 Drawings and Specifications . . . .314
1503.8 Procedure for Estimating Gray Water Discharge . . . . . . . . .314
1503.9 Gray Water System Components . . . . . . . . . . . . . . . . .315
1504.0 Subsurface Irrigation System Zones . . . . . . . . . . . . . . . .316
1504.1 General . . . . . . . . . . . . . . . . . . . . .316
California Mechanical Code High relevance — show source text
METAL VENT CONNECTOR DIAMETER –D (inch)|SINGLE-WALL METAL VENT CONNECTOR DIAMETER –****D (inch)|SINGLE-WALL METAL VENT CONNECTOR DIAMETER –D (inch)|SINGLE-WALL METAL VENT CONNECTOR DIAMETER –****D (inch)|SINGLE-WALL METAL VENT CONNECTOR DIAMETER –****D (inch)|SINGLE-WALL METAL VENT CONNECTOR DIAMETER –****D (inch)|SINGLE-WALL METAL VENT CONNECTOR DIAMETER –****D (inch)|SINGLE-WALL METAL VENT CONNECTOR DIAMETER –****D (inch)| |||8|8|8|9|9|9|10|10|10| |||APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU PER HOUR|APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU PER HOUR|APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU PER HOUR|APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU PER HOUR|APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU PER HOUR|APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU PER HOUR|APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU PER HOUR|APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU PER HOUR|APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU PER HOUR| |VENT
HEIGHT
_H _
(feet)|CONNECTOR
RISE
_R _
(feet)|FAN|FAN|NAT|FAN|FAN|NAT|FAN|FAN|NAT| |VENT
HEIGHT
_H _
(feet)|CONNECTOR
RISE
_R _
(feet)**|Min|Max|Max|Min|Max|Max|Min|Max|Max| |6|1
2
3|292
301
309|366
432
491|200
231
269|362
373
381|474
557
634|252
299
348|499
509
519|594
696
793|316
376
437| |8|1
2
3|313
323
332|407
465
509|207
238
274|387
397
407|530
607
663|263
309
356|529
540
551|672
766
838|331
391
450| |10|1
2CMC § 503.5.7. Medium relevance — show source text
(3) Water temperature reset is not required where valve position is used to comply with Section E 503.5.7. [ASHRAE 90.1:6.5.4.4]
E 503.5.7.5 Hydronic (Water Loop) Heat Pump and Water-Cooled Unitary Air Condi- tioners. Hydronic heat pumps and water-cooled unitary air-conditioners shall have a two-position automatic valve interlocked to shut off water flow
when the compressor is off.
Exception: Units employing fluid economizers.
[ASHRAE 90.1:6.5.4.5.1]
E 503.5.7.5.1 Controls. Hydronic heat pumps and water-cooled unitary air-conditioners having a total pump system power exceeding 5 hp (3.7 kW) shall have controls, devices, or both (such as variable speed control) that will result in pump motor demand of not more than 30 percent of design wattage at 50 percent of design water flow. [ASHRAE 90.1:6.5.4.5.2]
E 503.5.7.6 Pipe Sizing. Chilled-water and condenser-water piping shall be designed such that the design flow rate in each piping segment shall not exceed the values listed in Table E 503.5.7.6 for the
appropriate total annual hours of operation. Piping size selections for systems that operate under variable flow conditions (e.g., modulating two-way control valves at coils) and that contain variable-speed pump motors shall be permitted to be made from the “Variable Flow/Variable Speed” columns. All others shall be made from the “Other” columns.
Exceptions:
(1) Design flow rates exceeding the values in Table E 503.5.7.6 shall be permitted in specific sections of piping if the piping in question is not in the critical circuit at design conditions and is not predicted to be in the critical circuit during more than 30 percent of operating hours.
TABLE E 503.5.7.6 PIPING SYSTEM DESIGN MAXIMUM FLOW RATE (gallons per minute)
[ASHRAE 90.1: TABLE 6.5.4.6]
CMC § 301.6 Medium relevance — show source text
301.6 Personnel Protection. A metal guard shall be provided around exposed flywheels, fans, pulleys, belts, and moving machinery that are portions of a heating, ventilating, or refrigerating system. 301.7 OSHPD 1R. [OSHPD 1R] For OSHPD 1R, refer to Section 309 of California Existing Building Code for general requirements.
302.0 Materials – Standards and Alternates.
302.1 Minimum Standards. Listed pipe, pipe fittings, appliances, appurtenances, equipment, materials, and devices used in a mechanical system shall be listed (third-party certified) by a listing agency (accredited conformity assessment
body) as complying with the approved applicable recognized standards referenced in this code, and shall be free from defects. Unless otherwise provided for in this code, materials, appurtenances, or devices used or entering into the construction of mechanical systems, or parts thereof, shall be submitted to the Authority Having Jurisdiction for approval prior to being installed.
302.1.1 Marking. Each length of pipe and each pipe fitting, material, and device used in a mechanical system shall have cast, stamped, or indelibly marked on it any markings required by the applicable referenced standards and listing agency, and the manufacturer’s mark or name, which shall readily identify the manufacturer to the end user of the product. Where required by the approved standard that applies, the product shall be marked with the weight and the quality of the product. Materials and devices used or entering into the construction of mechanical systems, or parts thereof, shall be marked and identified in a manner satisfactory to the Authority Having Jurisdiction. Such marking shall be done by the manufacturer. Field markings shall not be acceptable.
Exception: Markings shall not be required on nipples created from cutting and threading of approved pipe.
302.1.2 Standards. Standards listed or referred to in this chapter or other chapters cover materials that will conform to the requirements of this code, where used in accordance with the limitations imposed in this or other chapters thereof and their listing. Where a standard covers materials of various grades, weights, quality, or configurations, the portion of the listed standard that is applicable shall be used. Design and materials for special conditions or materials not provided for herein shall be permitted to be used by special permission of the Authority Having Jurisdiction after the Authority Having Jurisdiction has been satisfied as to their adequacy. A list of mechanical standards that appear in specific sections of this code is referenced in Table 1801.1. Standards referenced in Table 1801.1 shall be applied as indicated in the applicable referenced section. A list of additional approved standards, publications, practices and guides that are not referenced in specific sections of this code appear in Table 1801.2.
302.1.3 Existing Buildings. In existing buildings or premises in which mechanical installations are to be altered, repaired, or renovated, the Authority Having Jurisdiction has discretionary powers to permit deviation from the provisions of this code, provided that such proposal to deviate is first submitted for proper determination in order that health and safety requirements, as they pertain to mechanical systems, shall be observed.
302.2 Alternate Materials and Methods of Construc- tion Equivalency. Nothing in this code is intended to pre
2025 CALIFORNIA MECHANICAL CODE 51
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CMC § 108.6 Medium relevance — show source text
[A] 108.6 Refunds. The applicable governing authority is authorized to establish a refund policy.
SECTION 109—INSPECTIONS
[A] 109.1 Inspection authority. The fire code official is authorized to enter and examine any building, structure, marine vessel, vehicle or premises in accordance with Section 104.4 for the purpose of enforcing this code.
[A] 109.2 Inspections. The fire code official is authorized to conduct such inspections as are deemed necessary to determine the extent of compliance with the provisions of this code and to approve reports of inspection by approved agencies or individuals. Reports of such inspections shall be prepared and submitted in writing for review and approval. Inspection reports shall be certified by a responsible officer of such approved agency or by the responsible individual. The fire code official is authorized to engage such expert opinion as deemed necessary to report on unusual, detailed or complex technical issues subject to the approval of the governing body.
[A] 109.2.1 Inspection requests. It shall be the duty of the holder of the permit or their duly authorized agent to notify the fire code official when work is ready for inspection. It shall be the duty of the permit holder to provide access to and means for inspections of such work that are required by this code.
[A] 109.2.2 Approval required. Work shall not be done beyond the point indicated in each successive inspection without first obtaining the approval of the fire code official. The fire code official, on notification, shall make the requested inspections and shall either indicate the portion of the construction that is satisfactory as completed, or notify the permit holder or his or her agent wherein the same fails to comply with this code. Any portions that do not comply shall be corrected, and such portion shall not be covered or concealed until authorized by the fire code official.
[A] 109.3 Concealed work. It shall be the duty of the permit applicant to cause the work to remain visible and able to be accessed for inspection purposes. Where any installation subject to inspection prior to use is covered or concealed without having first been inspected, the fire code official shall have the authority to require that such work be made visible and able to be accessed for inspection. Neither the fire code official nor the jurisdiction shall be liable for expense entailed in the removal or replacement of any material required to allow inspection.
[A] 109.4 Approvals. Approval as the result of an inspection shall not be construed to be an approval of a violation of the provisions of this code or of other ordinances of the jurisdiction. Inspections presuming to give authority to violate or cancel provisions of this code or of other ordinances of the jurisdiction shall not be valid.
SECTION 110—MAINTENANCE
[A] 110.1 Maintenance of safeguards. Where any device, equipment, system, condition, arrangement, level of protection, or any other feature is required for compliance with the provisions of this code, or otherwise installed, such device, equipment, system, condition, arrangement, level of protection, or other feature shall thereafter be continuously maintained in accordance with this code and applicable referenced standards.
[A] 110.2 Testing and operation. Equipment requiring periodic testing or operation to ensure maintenance shall be tested or operated as specified in this code.
[A] 110.2.1 Reinspection and testing. Where any work or installation does not pass an initial test or inspection, the necessary corrections shall be made so as to achieve compliance with this code. The work or installation shall then be resubmitted to the fire code official for inspection and testing.
CMC § 904.3 Medium relevance — show source text
Exception: In existing buildings, where the selling space is under 5000 square feet (465 m [2] ) no more than one check-out aisle complying with Section 11B- 904.3 shall be required .
TABLE 11B-227.2 —CHECK-OUT AISLES Col2 NUMBER OF CHECK-OUT AISLES OF EACH FUNCTION MINIMUM NUMBER OF CHECK-OUT AISLES OF EACH FUNCTION
REQUIRED TO COMPLY WITH_11B-_904.31 to 4 1 5 to 8 2 9 to 15 3 16 and over 3, plus 20 percent of additional aisles 11B- 227.2.1 Altered check-out aisles. Where check-out aisles are altered, at least one of each check-out aisle serving each function shall comply with Section 11B- 904.3 until the number of check-out aisles complies with Section 11B- 227.2.
11B- 227.3 Counters. Where provided, at least one of each type of sales counter and service counter shall comply with Section 11B- 904.4. Where counters are dispersed throughout the building or facility, counters complying with Section 11B- 904.4 also shall be dispersed.
11B- 227.4 Food service lines. Food service lines shall comply with Section 11B- 904.5. Where self-service shelves are provided, at least 50 percent, but no fewer than one, of each type provided shall comply with Section 11B- 308 .
11B- 227.5 Queues and waiting lines. Queues and waiting lines servicing counters or check-out aisles required to comply with Sections 11B- 904.3 or 11B- 904.4 shall comply with Section 11B- 403 .
SECTION 11B- 228—DEPOSITORIES, VENDING MACHINES, CHANGE MACHINES, MAIL BOXES, FUEL DISPENSERS AND ELECTRIC VEHICLE CHARGING STATIONS
11B- 228.1 General. Where provided, at least one of each type of depository, vending machine, change machine and fuel dispenser shall comply with Section 11B- 309 . Electric vehicle charging stations shall comply with Section 11B-228.3.
Exception: Drive-up only depositories shall not be required to comply with Section 11B- 309 .
11B- 228.2 Mail boxes. Where mail boxes are provided in an interior location, at least 5 percent, but no fewer than one, of each type shall comply with Section 11B- 309. In residential facilities, where mail boxes are provided for each residential dwelling unit, mail boxes complying with Section 11B- 309 shall be provided for each residential dwelling unit required to provide mobility features complying with Sections 11B- 809.2 through 11B- 809.4 and adaptable features complying with Sections 11B-809.6 through 11B-809.12.
11B-228.3 Electric vehicle charging stations.
CMC § 203.11 Medium relevance — show source text
11B- 203.11 Water slides. Water slides shall not be required to comply with these requirements or to be on an accessible route. An accessible route complying with Division 4 shall be provided to the ground- or floor-level entry points, where provided, of stairs, ladders or other means of reaching the raised elements or areas.
11B- 203.12 Animal containment areas. Animal containment areas that are not for public use shall not be required to comply with these requirements or to be on an accessible route. Animal containment areas for public use shall be on an accessible route.
11B- 203.13 Raised boxing or wrestling rings. Raised boxing or wrestling rings shall not be required to comply with these requirements or to be on an accessible route. An accessible route complying with Division 4 shall be provided to the ground- or floor-level entry points, where provided, of stairs, ladders or other means of reaching the raised elements or areas.
11B- 203.14 Raised diving boards and diving platforms. Raised diving boards and diving platforms shall not be required to comply with these requirements or to be on an accessible route. An accessible route complying with Division 4 shall be provided to the ground- or floor-level entry points, where provided, of stairs, ladders or other means of reaching the raised elements or areas.
SECTION 11B- 204—PROTRUDING OBJECTS
11B- 204.1 General. Protruding objects on circulation paths shall comply with Section 11B- 307 .
Exceptions:
Within areas of sport activity, protruding objects on circulation paths shall not be required to comply with Section 11B- 307 .
Within play areas, protruding objects on circulation paths shall not be required to comply with Section 11B- 307 provided that ground level accessible routes provide vertical clearance in compliance with Section 11B- 1008.2.
SECTION 11B- 205—OPERABLE PARTS
11B- 205.1 General. Operable parts on accessible elements, accessible routes, and in accessible rooms and spaces shall comply with Section 11B- 309 .
Exceptions:
Operable parts that are intended for use only by service or maintenance personnel shall not be required to comply with Section 11B- 309 .
Electrical or communication receptacles serving a dedicated use shall not be required to comply with Section 11B- 309 .
Reserved.
Floor electrical receptacles shall not be required to comply with Section 11B- 309 .
HVAC diffusers shall not be required to comply with Section 11B- 309 .
Except for light switches, where redundant controls are provided for a single element, one control in each space shall not be required to comply with Section 11B- 309 .
Cleats and other boat securement devices shall not be required to comply with Section 11B- 309.3.
Exercise machines and exercise equipment shall not be required to comply with Section 11B- 309 . 9. In residential dwelling units with mobility features where receptacles are provided in a kitchen at a corner work surface, one receptacle shall be located 36 inches (915 mm) from either wall at the inside corner.
2025 CALIFORNIA BUILDING CODE 11B-11
CMC § 506.8.1 Medium relevance — show source text
506.8.1 Loads. Duct supports shall be designed to carry the weight of the duct half filled with material. Where sprinkler protection is provided or cleaning of the duct will be performed, the hanger’s design shall include the weight of any expected liquid accumulation. Duct supports shall be designed to prevent placing loads on connected equipment. [NFPA 91:4.6.1 – 4.6.3]
506.8.2 Corrosion. Hangers and supports exposed to corrosive atmospheres shall be resistant to the corrosive atmospheres. [NFPA 91:4.6.4]
506.8.3 Vibration and Stress. To avoid vibration and stress on the duct, hangers and supports shall be securely fastened to the building or structure. [NFPA 91:4.6.5]
506.8.4 Expansion and Contraction. Hangers and supports shall be designed to allow for expansion and contraction. [NFPA 91:4.6.6]
506.9 Protection from Physical Damage. Ducts and exhaust equipment installed in locations where they are subject to physical damage shall be protected by guards.
506.10 Duct Clearances. Unless the conditions stipulated in Section 506.10.1 or Section 506.10.2 exist, all duct systems and system components shall have a clearance of at least 6 inches (152 mm) from stored combustible materials, and not less than [1] ⁄ 2 of an inch (13 mm) clearance from combustible construction. [NFPA 91:4.7.1]
506.10.1 Protection Provided. Where stored combustible material or combustible construction is protected from ductwork by the use of materials or products listed for protection purposes, clearance shall be maintained in accordance with those listings. [NFPA 91:4.7.1.1]
506.10.2 Systems Conveying Combustible Mate- rials. Unless the conditions stipulated in Section 506.10.3 exist, all duct systems and system components handling combustible materials shall have a clearance of not less than 18 inches (457 mm) from stored combustible materials or combustible construction. [NFPA 91:4.7.2]
506.10.3 Reduced Clearance Permitted. When the ductwork system is operating at 140°F (60°C) or below and is equipped with an approved automatic extinguishing system designed for the specific hazard, the clearance shall be permitted to be reduced to 6 inches (152 mm) from combustible materials and [1] ⁄ 2 of an inch (12.7 mm) from combustible construction. [NFPA 91:4.7.2.1]
506.10.4 Clearance Increases. All duct systems and system components operating at temperatures above 140°F (60°C) shall have clearances from stored combustible materials or combustible construction not less
than those listed in Table 506.10.4. [NFPA 91:4.7.3]
TABLE 506.10.4
BASIC MINIMUM CLEARANCES TO UNPROTECTED SURFACES
[NFPA 91: TABLE 4.7.3]
Frequently asked questions
Can I use an epoxy or sealant to stop a refrigerant or condensate leak?
No. § 309.2 expressly prohibits concealing cracks, holes, or other imperfections by using paint, tar, solvent cement or other leak‑sealing/repair agents; the proper repair or component replacement must be made and verified.
Do I have to follow the equipment manufacturer’s instructions exactly?
Yes. § 309.3 requires installations to be in accordance with the Code, applicable standards, and the manufacturer’s installation instructions; manufacturer instructions are part of the required compliance.
What does “accepted engineering practices” mean in practice?
It means using recognized calculation methods, referenced standards, listed materials, proper supports and good workmanship so the installation achieves the Code’s intended results — the general requirement is in § 309.1. For specifics, consult applicable referenced standards and the materials/marking requirements in the Code.
If the building is existing, can the AHJ allow deviations from these requirements?
The AHJ has discretionary powers in certain existing‑building situations to permit deviations, but any deviation must be formally approved by the AHJ and demonstrate equivalent safety/performance; the CMC contains provisions related to alternates and existing building approvals. The retrieved § 309 text itself does not list exceptions.
What should I include in construction documents to satisfy § 309.3?
At minimum: equipment schedules (manufacturer, model, nameplate info), location and clearances, duct/pipe routing and supports, service access, venting, condensate disposal and control methods, and references to manufacturer instructions and referenced standards. These documents must be approved by the AHJ before concealing work.
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