CMC · California Mechanical Code
Piping, hangers, and air‑system limits
This hub summarizes CMC requirements for supporting and protecting piping (materials, hanger sizes and spacing), fuel‑gas piping limits and air‑system constraints including return‑air and balancing, with key sections and tables cited.
Last reviewed: July 6, 2026
Overview
This portion of the California Mechanical Code (CMC) covers requirements for supporting and protecting piping and tubing (materials, hanger rod sizes, spacing and alignment), basic limits for fuel‑gas piping placement and support, and basic limits and balancing requirements for heating/cooling air systems. See the CMC provisions on hangers, supports and anchors at §313.0 for general support rules and hanger‑rod sizing (including Table 313.6) , fuel‑gas support, spacing and protective requirements at §1310.3.5 and Table 1310.3.5.1 , and air‑system limits such as return‑air restrictions and balancing at §311.0–§314.0 .
These rules matter because proper hangers, spacing, anchors and system limits control vibration, thermal movement, structural loads, and safety (including combustion‑air and fuel‑gas routing). The CMC cross‑references standards (for example MSS SP‑58 for hangers) and requires adherence to manufacturer instructions and the Authority Having Jurisdiction; fuel‑gas hangers and spacing are specifically called out to prevent undue strain and corrosion and to allow expansion/contraction . Where seismic performance or exceptions apply, the Building Code/ASCE provisions alter or add limits for hanger assemblies and pipe sizing — see the additional ASCE 7 piping provisions adopted in the Building Code for seismic exceptions (13.6.7.3) .
Key CMC reference points in this topic include §313.0 (Hangers, supports and anchors; Table 313.6), §1310.3.5 (fuel‑gas piping supports and spacing; Table 1310.3.5.1), §311.0–§314.0 (heating/cooling air system limits, return‑air limitations, and balancing), plus associated testing and condensate rules; consult those sections and the listed tables for spacing, rod sizes, and specific prohibitions and exceptions .
In this section
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 1310.3.4 High relevance — show source text
1310.3.4 Prohibited Locations. Gas piping inside any building shall not be installed in or through a clothes chute, chimney or gas vent, dumbwaiter, elevator shaft, or air duct, other than combustion air ducts. [NFPA 54:7.2.5]
Exception: Ducts used to provide ventilation air in accordance with Section 701.0 or to above-ceiling spaces in accordance with Section 1310.3.3.1.
1310.3.5 Hangers, Supports, and Anchors. Piping shall be supported with metal pipe hooks, metal pipe straps, metal bands, metal brackets, metal hangers, or building structural components, suitable for the size of piping, of adequate strength and quality, and located at intervals so as to prevent or damp out excessive vibration. Piping shall be anchored to prevent undue strains on connected appliances and equipment and shall not be supported by other piping. Pipe hangers and supports shall conform to the requirements of MSS SP-58. [NFPA 54:7.2.6.1]
1310.3.5.1 Spacing. Spacing of supports in gas piping installations shall not be greater than shown in Table 1310.3.5.1. Spacing of supports of CSST shall be in accordance with the CSST manufac turer’s instructions. [NFPA 54:7.2.6.2]
TABLE 1310.3.5.1
SUPPORT OF PIPING
[NFPA 54: TABLE 7.2.6.2]
STEEL PIPE,
NOMINAL SIZE
OF PIPE(inches)SPACING OF
SUPPORTS
(feet)NOMINAL SIZE
OF TUBING
SMOOTH WALL
(inches O.D.)SPACING OF
SUPPORTS
(feet)1⁄2 6 1⁄2 4
3⁄4 or 18 5⁄8 or3⁄4 6
11⁄4 or larger
(horizontal)10 7⁄8 or 1
(horizontal)8
11⁄4 or larger
(vertical)Every floor
level1 or larger
(vertical)Every floor
levelFor SI units: 1 inch = 25 mm, 1 foot = 304.8 mm
1310.3.5.2 Expansion and Contraction. Supports, hangers, and anchors shall be installed so as not to interfere with the free expansion and contraction of the piping between anchors. All parts of the supporting system shall be designed and installed so they are not disengaged by movement of the supported piping. [NFPA 54:7.2.6.3]
1310.3.5.3 Piping on Roofs. Gas piping installed on the roof surfaces shall be supported in accordance with Table 1310.3.5.1. Gas piping shall be elevated not less than 3½ inches (89 mm) above the roof surface. [NFPA 54:7.2.6.4.1, 7.2.6.4.2]
CMC § 13.3 High relevance — show source text
or
b. The duct is supported by individual rod hangers [3] / 8 inch (10 mm) or [1] / 2 inch (13 mm) in diameter, and each hanger in the duct run is 12 inches (305 mm) or less in length from the duct support point to the connection at the supporting structure, and the total weight supported by any single rod is 50 pounds (220 N) or less. 2. Design for the seismic forces and relative displacements of Section 13.3 shall not be required where provisions are made to avoid impact with other ducts or mechanical components or to protect the ducts in the event of such impact, the distribution system is positively attached to the structure; and HVACR ducts have a cross-sectional area of less than 6 square feet (0.557 m [2] ) and weigh 20 lb/ft (292 N/m) or less.
Components that are installed in line with the duct system and have an operating weight greater than 75 pounds (334 N), such as fans, terminal units, heat exchangers and humidifiers, shall be supported and laterally braced independent of the duct system, and such braces shall meet the force requirements of Section 13.3.1. Components that are installed in line with the duct system, have an operating weight of 75 pounds (334 N) or less, such as small terminal units, dampers, louvers and diffusers, and are otherwise not independently braced shall be positively attached with mechanical fasteners to the rigid duct on both sides. Piping and conduit attached to in-line equipment shall be provided with adequate flexibility to accommodate the seismic relative displacements of Section 13.3.2.
16-42 2025 CALIFORNIA BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
STRUCTURAL DESIGN
1617.12.16 ASCE 7, Section 13.6.7.3. Replace ASCE 7, Section 13.6.7.3 with the following:
13.6.7.3 Additional provisions for piping and tubing systems. A) Design for the seismic forces of Section 13.3 shall not be required for piping systems where flexible connections, expansion loops or other assemblies are provided to accommodate the relative displacement between component and piping, where the piping system is positively attached to the structure, and where any of the following conditions apply:
- Trapeze assemblies are supported by [3] / 8 -inch (10 mm) or [1] / 2 -inch (13-mm) diameter rod hangers not exceeding 12 inches (305 mm) in length from the pipe support point to the connection at the supporting structure, and no single pipe exceeds the diameter limits set forth in item 2b or 2 inches (50 mm) where I p is greater than 1.0 and the total weight supported by any single trapeze is 100 pounds (445 N) or less; or 2. Piping is supported by rod hangers and provisions are made to avoid impact with other structural or nonstructural components or to protect the piping in the event of such impact; or pipes are supported by individual rod hangers [3] / 8 inch (10 mm) or [1] / 2 inch (13 mm) in diameter, where each hanger in the pipe run is 12 inches (305 mm) or less in length from the pipe support point to the connection at the supporting structure,
CMC § 1617A.1.26 High relevance — show source text
1617A.1.26 ASCE 7, Section 13.6.7.3. Replace ASCE 7, Section 13.6.7.3 with the following:
13.6.7.3 Additional Provisions for Piping and Tubing Systems. A) Design for the seismic forces of Section 13.3 shall not be required for piping systems where flexible connections, expansion loops or other assemblies are provided to accommodate the relative displacement between component and piping, where the piping system is positively attached to the structure, and where any of the following conditions apply:
- Trapeze assemblies are supported by [3] / 8 -inch (10 mm) or [1] / 2 -inch (13 mm) diameter rod hangers not exceeding 12 inches (305 mm) in length from the pipe support point to the connection at the supporting structure, and no single pipe exceeds the diameter limits set forth in item 2b below or 2 inches (50 mm) where I p is greater than 1.0 and the total weight supported by any single trapeze is 100 pounds (445 N) or less; or 2. Piping is supported by rod hangers and provisions are made to avoid impact with other structural or nonstructural components or to protect the piping in the event of such impact; or pipes are supported by individual rod hangers [3] / 8 inch (10 mm) or [1] / 2 inch (13 mm) in diameter, where each hanger in the pipe run is 12 inches (305 mm) or less in length from the pipe support point to the connection at the supporting structure, and the total weight supported by any single hanger is 50 pounds (220 N) or less. In addition, the following limitations on the size of piping shall be observed: a. In structures assigned to Seismic Design Category D, E or F where I p is greater than 1.0, the nominal pipe size shall be 1 inch (25 mm) or less. b. In structures assigned to Seismic Design Category D, E or F where I p = 1.0, the nominal pipe size shall be 3 inches (80 mm) or less. 3. Pneumatic tube systems supported with trapeze assemblies using [3] / 8 inch (10 mm) in diameter rod hangers not exceeding 12 inches (305 mm) in length from the tube support point to the connection at the supporting structure and the total weight supported by any single trapeze is 100 pounds (445 N) or less. 4. Pneumatic tube systems supported by individual rod hangers [3] / 8 inch (10 mm) or [1] / 2 inch (13 mm) in diameter, and each hanger in the run is 12 inches (305 mm) or less in length from the tube support point to the connection at the supporting structure, and the total weight supported by any single rod is 50 pounds (220 N) or less. B) Flexible connections in piping required in Section 13.6.7.3 are not required where pipe is rigidly attached to the same floor or wall that provides vertical and lateral support for the equipment, or to a fixture. C) Flexible connections in piping are required at seismic separation joints and shall be detailed to accommodate the seis- mic relative displacements at connections.
CMC § 312.0 High relevance — show source text
312.0 Plumbing Connections. 312.1 General. Water supply, sanitary drainage, and backflow protection shall be in accordance with the California Plumbing Code .
313.0 Hangers, Supports, and Anchors. 313.1 General. Piping, tubing, appliances, and appurtenances shall be supported in accordance with this code, the manufacturer’s installation instructions, and in accordance with the Authority Having Jurisdiction. Seismic restraints shall be in accordance with the building code. 313.2 Material. Hangers, supports, and anchors shall be of sufficient strength to support the weight of the pipe or tubing and its contents. Piping or tubing shall be isolated from incompatible materials.
313.3 Suspended Piping. Suspended piping or tubing shall be supported at intervals not to exceed those shown in Table 313.3.
313.4 Alignment. Piping or tubing shall be supported in such a manner as to maintain its alignment and prevent sagging.
313.5 Underground Installation. Piping or tubing in the ground shall be laid on a firm bed for its entire length; where other support is otherwise provided, it shall be approved in accordance with Section 302.0.
313.6 Hanger Rod Sizes. Hanger rod sizes shall be not smaller than those shown in Table 313.6.
TABLE 313.6
HANGER ROD SIZES
PIPE AND TUBE SIZE
(inches)ROD SIZES
(inches)
1⁄2 - 43⁄8
5 - 81⁄2
10 - 125⁄8 For SI units: 1 inch = 25.4 mm
313.7 Gas Piping. Gas piping shall be supported by metal straps or hooks at intervals not to exceed those shown in Table 1310.3.5.1.
314.0 Balancing.
314.1 General. Heating, ventilating, and air-conditioning systems (including hydronic systems) shall be balanced in accordance with one of the following methods:
TABLE 313.6
HANGER ROD SIZES
(1) AABC National Standards for Total System Balance
(2) ACCA Manual B
(3) ASHRAE 111
(4) NEBB Procedural Standards for Testing Adjusting Balancing of Environmental Systems
(5) SMACNA HVAC Systems Testing, Adjusting, and Balancing
315.0 Louvers in Hurricane Prone Regions.
315.1 General. Louvers located in areas within hurricane prone regions that are within 1 mile (2 km) of the coastal mean high water line where the basic wind speed is 110 miles per hour (mi/h) (49.2 m/s) or more; or portions of hurricane-prone regions where the basic wind speed is 120 mi/h (53.6 m/s) or more; or Hawaii, shall be tested in accordance with Section 315.1.1 and Section 315.1.2.
315.1.1 Testing. Louvers that protect air intake or exhaust openings shall be tested in accordance with AMCA 550 for resistance to wind-driven rain.
315.1.2 Impact Resistance Test. Upon request by the Authority Having Jurisdiction, louvers protecting intake and exhaust ventilation ducts that are not fixed in the
CMC § 1617.12.16 Medium relevance — show source text
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
STRUCTURAL DESIGN
1617.12.16 ASCE 7, Section 13.6.7.3. Replace ASCE 7, Section 13.6.7.3 with the following:
13.6.7.3 Additional provisions for piping and tubing systems. A) Design for the seismic forces of Section 13.3 shall not be required for piping systems where flexible connections, expansion loops or other assemblies are provided to accommodate the relative displacement between component and piping, where the piping system is positively attached to the structure, and where any of the following conditions apply:
- Trapeze assemblies are supported by [3] / 8 -inch (10 mm) or [1] / 2 -inch (13-mm) diameter rod hangers not exceeding 12 inches (305 mm) in length from the pipe support point to the connection at the supporting structure, and no single pipe exceeds the diameter limits set forth in item 2b or 2 inches (50 mm) where I p is greater than 1.0 and the total weight supported by any single trapeze is 100 pounds (445 N) or less; or 2. Piping is supported by rod hangers and provisions are made to avoid impact with other structural or nonstructural components or to protect the piping in the event of such impact; or pipes are supported by individual rod hangers [3] / 8 inch (10 mm) or [1] / 2 inch (13 mm) in diameter, where each hanger in the pipe run is 12 inches (305 mm) or less in length from the pipe support point to the connection at the supporting structure, and the total weight supported by any single hanger is 50 pounds (220 N) or less. In addition, the following limitations on the size of piping shall be observed: a. In structures assigned to Seismic Design Category D, E or F where I p is greater than 1.0, the nominal pipe size shall be 1 inch (25 mm) or less. b. In structures assigned to Seismic Design Category D, E or F where I p = 1.0, the nominal pipe size shall be 3 inches (80 mm) or less. 3. Pneumatic tube systems supported with trapeze assemblies using [3] / 8 -inch (10 mm) diameter rod hangers not exceeding 12 inches (305 mm) in length from the tube support point to the connection at the supporting structure and the total weight supported by any single trapeze is 100 pounds (445 N) or less. 4. Pneumatic tube systems supported by individual rod hangers [3] / 8 inch (10 mm) or [1] / 2 inch (13 mm) in diameter, and each hanger in the run is 12 inches (305 mm) or less in length from the tube support point to the connection at the supporting structure, and the total weight supported by any single rod is 50 pounds (220 N) or less. B) Flexible connections in piping required in Section 13.6.7.3 are not required where pipe is rigidly attached to the same floor or wall that provides vertical and lateral support for the equipment, or to a fixture. C) Flexible connections in piping are required at seismic separation joints and shall be detailed to accommodate the seis- mic relative displacements at connections.
CMC § 1310.3.1 Medium relevance — show source text
1310.3.1 Protective Coating. Where piping is in contact with a material or an atmosphere corrosive to the piping system, the piping and fittings shall be coated with a corrosion-resistant material. Any such coating used on piping or components shall not be considered as adding strength to the system. [NFPA 54:7.2.2]
1310.3.2 Building Structure. The installation of gas piping shall not cause structural stresses within building components to exceed allowable design limits. Approval shall be obtained before any beams or joists are cut or notched. [NFPA 54:7.2.3.1 – 7.2.3.2]
1310.3.3 Gas Piping to be Sloped. Piping for other than dry gas conditions shall be sloped not less than [1] ⁄ 4 inch in 15 feet (1.4 mm/m) to prevent traps. [NFPA 54:7.2.4]
1310.3.3.1 Ceiling Locations. Gas piping shall be permitted to be installed in accessible spaces between a fixed ceiling and a dropped ceiling, whether or not such spaces are used as a plenum. Valves shall not be located in such spaces.
Exception: Appliance or equipment shutoff valves required by this code shall be permitted to be installed in accessible spaces containing vented appliances.
1310.3.4 Prohibited Locations. Gas piping inside any building shall not be installed in or through a clothes chute, chimney or gas vent, dumbwaiter, elevator shaft, or air duct, other than combustion air ducts. [NFPA 54:7.2.5]
Exception: Ducts used to provide ventilation air in accordance with Section 701.0 or to above-ceiling spaces in accordance with Section 1310.3.3.1.
1310.3.5 Hangers, Supports, and Anchors. Piping shall be supported with metal pipe hooks, metal pipe straps, metal bands, metal brackets, metal hangers, or building structural components, suitable for the size of piping, of adequate strength and quality, and located at intervals so as to prevent or damp out excessive vibration. Piping shall be anchored to prevent undue strains on connected appliances and equipment and shall not be supported by other piping. Pipe hangers and supports shall conform to the requirements of MSS SP-58. [NFPA 54:7.2.6.1]
1310.3.5.1 Spacing. Spacing of supports in gas piping installations shall not be greater than shown in Table 1310.3.5.1. Spacing of supports of CSST shall be in accordance with the CSST manufac turer’s instructions. [NFPA 54:7.2.6.2]
TABLE 1310.3.5.1
SUPPORT OF PIPING
[NFPA 54: TABLE 7.2.6.2]
CMC § 16A-40 Medium relevance — show source text
16A-40 2025 CALIFORNIA BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
STRUCTURAL DESIGN
the duct system and associated components, the duct system is positively attached to the structure, and where one of the following apply: a. Trapeze assemblies with [3] / 8 -inch (10 mm) or [1] / 2 -inch (13 mm) diameter rod hangers not exceeding 12 inches (305 mm) in length from the duct support point to the connection at the supporting structure are used to support duct, and the total weight supported by any single trapeze is less than 10 lb/ft (146 N/m) and 100 pounds or less; or b. The duct is supported by individual rod hangers [3] / 8 inch (10 mm) or [1] / 2 inch (13 mm) in diameter, and each hanger in the duct run is 12 inches (305 mm) or less in length from the duct support point to the connection at the supporting structure, and the total weight supported by any single rod is 50 pounds (220 N) or less. 2. Design for the seismic forces and relative displacements of Section 13.3 shall not be required where provisions are made to avoid impact with other ducts or mechanical components or to protect the ducts in the event of such impact, the distribution system is positively attached to the structure; and HVACR ducts have a cross-sectional area of less than 6 square feet (0.557 m [2] ) and weigh 20 lb/ft (292 N/m) or less.
Components that are installed in line with the duct system and have an operating weight greater than 75 pounds (334 N), such as fans, terminal units, heat exchangers and humidifiers, shall be supported and laterally braced independent of the duct system, and such braces shall meet the force requirements of Section 13.3.1. Components that are installed in line with the duct system, have an operating weight of 75 pounds (334 N) or less, such as small terminal units, dampers, louvers and diffusers, and are otherwise not independently braced shall be positively attached with mechanical fasteners to the rigid duct on both sides. Piping and conduit attached to in-line equipment shall be provided with adequate flexibility to accommodate the seismic relative displacements of Section 13.3.2.
1617A.1.26 ASCE 7, Section 13.6.7.3. Replace ASCE 7, Section 13.6.7.3 with the following:
13.6.7.3 Additional Provisions for Piping and Tubing Systems. A) Design for the seismic forces of Section 13.3 shall not be required for piping systems where flexible connections, expansion loops or other assemblies are provided to accommodate the relative displacement between component and piping, where the piping system is positively attached to the structure, and where any of the following conditions apply:
- Trapeze assemblies are supported by [3] / 8 -inch (10 mm) or [1] / 2 -inch (13 mm) diameter rod hangers not exceeding 12 inches (305 mm) in length from the pipe support point to the connection at the supporting structure, and no single pipe exceeds the diameter limits set forth in item 2b below or 2 inches (50 mm) where I p _is greater than 1.
CMC § 310.1 Medium relevance — show source text
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
313.0 Hangers, Supports, and Anchors . . 59
313.1 General. . . . . . . . . . . . . . . . . . . . . . 59
313.2 Material. . . . . . . . . . . . . . . . . . . . . . 59
313.3 Suspended Piping . . . . . . . . . . . . . 59
313.4 Alignment . . . . . . . . . . . . . . . . . . . . 59
313.5 Underground Installation . . . . . . . . 59
313.6 Hanger Rod Sizes . . . . . . . . . . . . . 59
Table 313.6 Hanger Rod Sizes . . . . . . . . . . . . . 59
313.7 Gas Piping . . . . . . . . . . . . . . . . . . . 59
314.0 Balancing . . . . . . . . . . . . . . . . . . . . 59
314.1 General. . . . . . . . . . . . . . . . . . . . . . 59
315.0 Louvers in Hurricane Prone
Regions . . . . . . . . . . . . . . . . . . . . . 59
315.1 General. . . . . . . . . . . . . . . . . . . . . . 59
2025 CALIFORNIA MECHANICAL CODE
316.0 Protection of Piping, Tubing, Materials, and Structures . . . . . . . . 59
316.1 General. . . . . . . . . . . . . . . . . . . . . . 59
CMC § 1210.3.4 Medium relevance — show source text
Exception: Appliance or equipment shutoff valves required by this code shall be permitted to be installed in accessible spaces containing vented appliances. 1210.3.4 Prohibited Locations. Gas piping inside any building shall not be installed in or through a clothes chute, chimney or gas vent, dumbwaiter, elevator shaft, or air duct, other than combustion air ducts. [NFPA 54:7.2.5]
Exception: Ducts used to provide ventilation air in accordance with Section 506.0 or to above-ceiling spaces in accordance with Section 1210.3.3.1.
1210.3.5 Hangers, Supports, and Anchors. Piping shall be supported with metal pipe hooks, metal pipe straps, metal bands, metal brackets, metal hangers, or building structural components, suitable for the size of piping, of adequate strength and quality, and located at intervals so as to prevent or damp out excessive vibration. Piping shall be anchored to prevent undue strains on connected appliances and equipment and shall not be supported by other piping. Pipe hangers and supports shall conform to the requirements of MSS SP-58. [NFPA 54:7.2.6.1] 1210.3.5.1 Spacing. Spacing of supports in gas piping installations shall not be greater than shown in Table 1210.3.5.1. Spacing of supports of CSST shall be in accordance with the CSST manufacturer’s instructions. [NFPA 54:7.2.6.2]
TABLE 1210.3.5.1
SUPPORT OF PIPING
[NFPA 54: TABLE 7.2.6.2]
STEEL PIPE,
NOMINAL SIZE
OF PIPE
(inches)SPACING OF
SUPPORTS
(feet)NOMINAL SIZE
OF TUBING
SMOOTH WALL
(inches O.D.)SPACING OF
SUPPORTS
(feet)
1⁄26 1⁄2 4 3⁄4 or 1 8 5⁄8 or3⁄4 6
11⁄4 or larger
(horizontal)10 7⁄8 or 1
(horizontal)8
11⁄4 or larger
(vertical)Every floor
level1 or larger
(vertical)Every floor
levelFor SI units: 1 inch = 25 mm, 1 foot = 304.8 mm
CMC § 313.0 Medium relevance — show source text
313.0 Hangers, Supports, and Anchors. 313.1 General. Piping, tubing, fixtures, appliances, and appurtenances shall be supported in accordance with this code, the manufacturer’s installation instructions, and in accordance with the Authority Having Jurisdiction. Seismic restraints shall be in accordance with the building code. 313.2 Material. Hangers, supports, and anchors shall be of sufficient strength to support the weight of the pipe or tubing and its contents. Piping or tubing shall be isolated from incompatible materials. 313.3 Suspended Piping. Suspended piping shall be supported at intervals not to exceed those shown in Table 313.3. 313.4 Alignment. Piping shall be supported in such a manner as to maintain its alignment and prevent sagging. 313.5 Underground Installation. Piping in the ground shall be laid on a firm bed for its entire length; where other support is otherwise provided, it shall be approved in accordance with Section 301.2.
313.6 Hanger Rod Sizes. Hanger rod sizes shall be not smaller than those shown in Table 313.6.
TABLE 313.6
HANGER ROD SIZES
PIPE AND TUBE SIZE
(inches)ROD SIZE
(inches)
1⁄2 – 43⁄8
5 – 81⁄2
10 – 125⁄8 For SI units: 1 inch = 25.4 mm
313.7 Gas Piping. Gas piping shall be supported by metal straps or hooks at intervals not to exceed those shown in Table 1210.3.5.1.
313.8 [OSHPD 1, 2, 3, 4 & 5] Refer to Title 24, Part 2 of the California Building Code for seismic anchorage and bracing requirements and accommodations for building displace-
ments.
314.0 Trenching, Excavation, and Backfill.
314.1 Trenches. Trenches deeper than the footing of a building or structure, and paralleling the same, shall be located not less than 45 degrees (0.79 rad) from the bottom exterior edge of the footing, or as approved in accordance with Section 301.0.
314.2 Tunneling and Driving. Tunneling and driving shall be permitted to be done in yards, courts, or driveways of a building site. Where sufficient depth is available to permit, tunnels shall be permitted to be used between open-cut trenches.
Tunnels shall have a clear height of 2 feet (610 mm) above the pipe and shall be limited in length to one-half the depth of the trench, with a maximum length of 8 feet (2438 mm). Where pipes are driven, the drive pipe shall be not less than one size larger than the pipe to be laid.
314.3 Open Trenches. Excavations required to be made for the installation of a building drainage system or part thereof, within the walls of a building, shall be open trench work and shall be kept open until the piping has been inspected, tested, and accepted.
CMC § 0.03 Medium relevance — show source text
(5) A closet, bathroom, toilet room, kitchen, garage, boiler room, furnace room, or unconditioned attic.
(6) Rooms or spaces containing a fuel-burning appliance therein. Where such room or space serves as source of return-air.
Exceptions:
(1) This shall not apply to fireplaces, fireplace appliances, residential cooking appliances, direct vent appliances, enclosed furnaces, and domestic-type clothes dryers installed within the room or space.
(2) This shall not apply to a gravity-type or listed vented wall heating or cooling air system.
(3) This shall not apply to a blower-type heating or cooling air system installed in accordance with the following requirements:
(a) Where the return air is taken from a room or space having a volume exceeding 1 cubic foot (0.03 m [3] ) for each 10 Btu/h (0.003 kW) fuel input rating of fuel-burning appliances therein.
(b) Not less than 75 percent of the supply air is discharged back into the same room or space.
(c) Return-air inlets shall not be located within 10 feet (3048 mm) from an appliance firebox or draft diverter in the same enclosed room or confined space.
311.4 Return-Air Limitations. Return air from one dwelling unit shall not discharge into another dwelling unit through the heating or cooling air system.
58 2025 CALIFORNIA MECHANICAL CODE
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GENERAL REGULATIONS
311.5 California Energy Code Requirements for Res- idential Air Filtration. In mechanically ventilated residen- tial buildings, air filters shall be provided to clean outdoor air and return air prior to its delivery to occupied spaces where specified in California Energy Code Sections 150.0(m)12 and 160.2(b). The air filters shall comply with California Energy Code requirements for labeling, ventilation system design and installation, air filter efficacy, and air filter pressure drop.
312.0 Plumbing Connections. 312.1 General. Water supply, sanitary drainage, and backflow protection shall be in accordance with the California Plumbing Code .
313.0 Hangers, Supports, and Anchors. 313.1 General. Piping, tubing, appliances, and appurtenances shall be supported in accordance with this code, the manufacturer’s installation instructions, and in accordance with the Authority Having Jurisdiction. Seismic restraints shall be in accordance with the building code. 313.2 Material. Hangers, supports, and anchors shall be of sufficient strength to support the weight of the pipe or tubing and its contents. Piping or tubing shall be isolated from incompatible materials.
313.3 Suspended Piping. Suspended piping or tubing shall be supported at intervals not to exceed those shown in Table 313.3.
313.4 Alignment. Piping or tubing shall be supported in such a manner as to maintain its alignment and prevent sagging.
313.5 Underground Installation. Piping or tubing in the ground shall be laid on a firm bed for its entire length; where other support is otherwise provided, it shall be approved in accordance with Section 302.0.
313.6 Hanger Rod Sizes. Hanger rod sizes shall be not smaller than those shown in Table 313.6.
CMC § 7.2.1 Medium relevance — show source text
(4) Where piping is encased in a protective pipe sleeve, the annular spaces between the gas piping and the sleeve and between the sleeve and the wall opening shall be sealed.
(5) Piping installed outdoors shall be elevated not less than 3½ inches (89 mm) above the ground.
(6) Sealing materials shall be compatible with the piping and sleeve. [NFPA 54:7.2.1] 1210.3.1 Protective Coating. Where piping is in contact with a material or an atmosphere corrosive to the piping system, the piping and fittings shall be coated with a corrosion-resistant material. Any such coating used on piping or components shall not be considered as adding strength to the system. [NFPA 54:7.2.2] 1210.3.2 Building Structure. The installation of gas piping shall not cause structural stresses within building components to exceed allowable design limits. Approval shall be obtained before any beams or joists are cut or notched. [NFPA 54:7.2.3.1 – 7.2.3.2] 1210.3.3 Gas Piping to be Sloped. Piping for other than dry gas conditions shall be sloped not less than [1] ⁄ 4 inch in 15 feet (6.4 mm in 4.6 m) to prevent traps. [NFPA 54:7.2.4] 1210.3.3.1 Ceiling Locations. Gas piping shall be permitted to be installed in accessible spaces between a fixed ceiling and a dropped ceiling, whether or not such spaces are used as a plenum. Valves shall not be located in such spaces.
Exception: Appliance or equipment shutoff valves required by this code shall be permitted to be installed in accessible spaces containing vented appliances. 1210.3.4 Prohibited Locations. Gas piping inside any building shall not be installed in or through a clothes chute, chimney or gas vent, dumbwaiter, elevator shaft, or air duct, other than combustion air ducts. [NFPA 54:7.2.5]
Exception: Ducts used to provide ventilation air in accordance with Section 506.0 or to above-ceiling spaces in accordance with Section 1210.3.3.1.
1210.3.5 Hangers, Supports, and Anchors. Piping shall be supported with metal pipe hooks, metal pipe straps, metal bands, metal brackets, metal hangers, or building structural components, suitable for the size of piping, of adequate strength and quality, and located at intervals so as to prevent or damp out excessive vibration. Piping shall be anchored to prevent undue strains on connected appliances and equipment and shall not be supported by other piping. Pipe hangers and supports shall conform to the requirements of MSS SP-58. [NFPA 54:7.2.6.1] 1210.3.5.1 Spacing. Spacing of supports in gas piping installations shall not be greater than shown in Table 1210.3.5.1. Spacing of supports of CSST shall be in accordance with the CSST manufacturer’s instructions. [NFPA 54:7.2.6.2]
TABLE 1210.3.5.1
SUPPORT OF PIPING
[NFPA 54: TABLE 7.2.6.2]
Frequently asked questions
What spacing and rod size rules apply to suspended piping?
Spacing and hanger‑rod size limits are in §313.0 (see Table 313.6 for minimum hanger‑rod sizes and Table 313.3 for support spacing) and fuel‑gas spacing is specified in Table 1310.3.5.1; hangers must be sized for the pipe, resist vibration, and allow for thermal movement .
Do fuel‑gas lines have special hanger or routing prohibitions?
Yes. Fuel‑gas piping must meet the support and spacing rules in §1310.3.5 (including elevated roof clearances and prohibited locations such as air ducts), must conform to MSS SP‑58 for hangers, and must allow for expansion/contraction and protection from corrosion or structural stress .
How do air‑system limits interact with balancing and return‑air rules?
Air‑system limits (return‑air sources, allowed locations, and filtration) are in §311.0 and related sections; balancing requirements for HVAC and hydronic systems are in §314.0 and reference industry standards (AABC, ACCA, ASHRAE 111, NEBB, SMACNA) for testing and balancing procedures .
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