CMC · California Mechanical Code
How do I size gas piping (tables, equations, altitude adjustments)?
For a homeowner: the California Mechanical Code says your gas lines must be sized to handle the total of all appliance inputs (or use code table defaults if an appliance rating isn’t shown), you must convert Btu/h to cubic feet using the local gas heating value from your supplier, adjust for altitude above 2,000 ft, and then pick the pipe size from the code’s tables or equations so every appliance still gets its required inlet pressure.
Last reviewed: July 6, 2026
What the code requires — 2–4 sentences
Gas piping must be sized so the system can supply the maximum gas demand and deliver gas to each appliance at or above the appliance’s minimum inlet pressure — see § 1308.3 . The required volumetric flow rate is the sum of the maximum inputs of the appliances served and must be adjusted for altitude when the installation is above 2,000 feet (610 m) — see § 1308.3.1 . When an appliance rating is not marked, use Table 1308.3.1 (Approximate Gas Input for Typical Appliances) to estimate inputs .
The single most important rule: size piping on the sum of the appliances’ maximum inputs (convert to volumetric flow), adjust for altitude above 2,000 ft, and then choose pipe sizes from the code tables or equations so each appliance still sees its required minimum inlet pressure. See § 1308.3 and § 1308.3.1.
Requirements in detail
1) Basis for sizing
- “Maximum gas demand” = the sum of the maximum rated input (Btu/h) of every appliance on the system; that total is the starting point for sizing. § 1308.3.1 requires this and the volumetric flow to be adjusted for altitude above 2,000 ft (610 m).
- If an appliance’s input rating is not indicated, the code allows using the approximate inputs listed in Table 1308.3.1.
- The code assumes all appliances could operate simultaneously unless you use an approved load diversity allowance (the Exception in § 1308.3.1).
2) How to convert appliance input to volumetric flow
- The code requires converting appliance input (Btu/h) to gas volumetric flow (ft3/h or m3/h) by dividing by the local average heating value (Btu per cubic foot) of the gas. That heating value must be obtained from the serving gas supplier (see related conversion guidance in the fuel-gas sections).
3) Allowed sizing methods (high level)
- The piping may be sized using: the pipe sizing tables or sizing equations in the chapter, manufacturer’s listed tables, or engineering methods — see § 1308.3.2 (note: this section appears adjacent to §1308.3 in the code).
Quick reference table — decision‑relevant thresholds/values
| Decision item | Value / action | Code Reference |
|---|---|---|
| Basis for sizing | Sum of maximum appliance inputs (assume simultaneous operation unless diversity is used) | § 1308.3.1 |
| Altitude threshold for adjustment | Above 2,000 ft (610 m) — volumetric flow must be adjusted | § 1308.3.1 |
| Use this when appliance rating unknown | Table 1308.3.1 — approximate inputs (Btu/h) for typical appliances | Table 1308.3.1 |
| Convert Btu/h → ft3/h | Divide appliance Btu/h by local Btu/ft3 heating value (get value from gas supplier) | See fuel-gas volume conversion guidance (e.g., §1314.3) |
| Permitted sizing methods | Code tables/equations in chapter, listed manufacturer tables, or engineering methods | § 1308.3.2 |
Exceptions & special cases
- Load diversity: The code allows using established diversity factors instead of the sum of all maximum inputs (this is an exception within § 1308.3.1) — but diversity must be established/approved.
- Unmarked appliance inputs: If an appliance’s input rating is unknown, the code explicitly allows using Table 1308.3.1 to estimate typical inputs.
- Altitude: The code requires an adjustment for altitude above 2,000 ft but does not give a single numeric multiplier inside § 1308.3.1; for full engineering sizing (including altitude/density effects) the code points users to the chapter’s sizing equations and factors (see the pipe sizing equations and factors elsewhere in the chapter).
If you need to apply altitude/density corrections numerically, the code’s sizing equations and correction factors in the piping-sizing portion of the chapter (e.g., the Cr/Y factors and sizing equations) should be used — those appear in the chapter’s sizing-equation tables and text.
Common mistakes
- Assuming the meter size or service pressure alone governs pipe sizing — the code requires sizing by actual maximum gas demand and allowable pressure drop so each appliance gets its minimum inlet pressure (§ 1308.3).
- Forgetting to get the local Btu per cubic foot heating value from the gas supplier before converting Btu/h to ft3/h — the code requires that conversion be based on the local gas heating value (see conversion guidance).
- Ignoring altitude: failing to adjust volumetric flow when installations are above 2,000 ft (610 m) violates § 1308.3.1.
- Using appliance nameplate Btu only and not verifying the inlet pressure or allowable pressure drop; the sizing must ensure each appliance receives at least its minimum rated supply pressure (§ 1308.3).
Worked example — concrete scenario (demonstration only)
Scenario: a single‑family dwelling with these appliances (inputs from Table 1308.3.1 when not marked):
- Furnace: 100,000 Btu/h
- Water heater: 40,000 Btu/h
- Range: 65,000 Btu/h
Total nameplate/input sum = 205,000 Btu/h (this is the maximum gas demand per § 1308.3.1) .
Step 1 — Convert to volumetric flow:
- The code requires dividing the Btu/h sum by the local heating value (Btu/ft3) to get ft3/h. The code requires obtaining that heating value from the gas supplier (do not assume): see the chapter guidance on volume conversion. For this example only, assume the local gas heating value is 1,000 Btu/ft3 (example assumption — obtain actual from supplier). Then:
- 205,000 Btu/h ÷ 1,000 Btu/ft3 = 205 ft3/h.
Step 2 — Altitude check:
- If the site is above 2,000 ft (610 m), the code requires an altitude adjustment to the volumetric flow before selecting pipe sizes (§ 1308.3.1). This example assumes sea level (no adjustment). If above 2,000 ft, proceed to the chapter’s sizing equations/correction factors (see sizing-equation tables and Cr/Y factors) to determine the correct volumetric rate to use.
Step 3 — Select pipe size:
- With the computed volumetric flow (example 205 ft3/h) and the measured or tabulated run length, use the code’s pipe sizing tables or sizing equations in the chapter to pick the minimum internal pipe diameter that will supply the load while keeping pressure at or above appliance minimum. The code permits using the chapter tables or equations (or listed manufacturer’s tables or engineering methods) — see § 1308.3.2 and the chapter tables (e.g., the pipe sizing tables that follow the sizing equations).
Note: the numeric conversion and final pipe selection in this worked example used an assumed heating value solely for illustration. The code requires the actual heating value from the serving gas supplier and, where necessary, use of the chapter sizing tables/equations (and altitude corrections) to finalize pipe sizes.
Related provisions (quick list)
- § 1308.3.2 — permitted sizing methods (tables, equations, engineering methods).
- § 1308.3.3 — allowable pressure drop: design pressure loss must ensure each appliance gets its required minimum inlet pressure.
- Table 1308.3.1 — approximate gas input (Btu/h) for typical appliances (use when nameplate rating is missing).
- § 1314.3 — converting Btu/h to cubic feet per hour; obtain average Btu per cubic foot from the serving gas supplier.
- Table 1315.3 / § 1315.3 — sizing-equation factors (Cr and Y) and sizing equations used for engineering methods and altitude/density corrections in the chapter.
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 5.5.2.4 High relevance — show source text
Threaded copper, copper alloy, or aluminum alloy pipe shall not be used with gases corrosive to such material. [NFPA 54:5.5.2.4]
1308.4.2.4 Aluminum Alloy Pipe. Aluminum alloy pipe shall comply with ASTM B241 (except that the use of alloy 5456 is prohibited), and shall be marked at each end of each length indicating compliance. Aluminum alloy pipe shall be coated to protect against external corrosion where it is in contact with masonry, plaster, or insulation or is subject to repeated wettings by such liquids as water, detergents, or sewage. [NFPA 54:5.5.2.5]
Aluminum alloy pipe shall not be used in exterior locations or underground. [NFPA 54:5.5.2.6]
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ular supply shall be permitted to be used for this purpose.
[NFPA 54:5.2.2.1 – 5.2.2.2] 1308.3 Sizing of Gas Piping Systems. Gas piping systems shall be of such size and so installed as to provide a supply of gas sufficient to meet the maximum demand and supply gas to each appliance inlet at not less than the minimum supply pressure required by the appliance. [NFPA 54:5.3.1]
1308.3.1 Maximum Gas Demand. The volumetric flow rate of gas to be provided shall be the sum of the maximum input of the appliances served. The volumetric flow rate of gas to be provided shall be adjusted for altitude where the installation is above 2 000 feet (610 m). [NFPA 54:5.3.2.1 – 5.3.2.2] Where the input rating is not indicated, the gas supplier, appliance manufacturer, or a qualified agency shall be contacted or the rating from Table 1308.3.1 shall be used for estimating the volumetric flow rate of gas to be supplied. The total connected hourly load shall be used as the basis for piping sizing, assuming all appliances are operating at full capacity simultaneously. Exception: Sizing shall be permitted to be based upon established load diversity factors. [NFPA 54:5.3.2.3] 1308.3.2 Sizing Methods. Gas piping shall be sized in accordance with one of the following: (1) Pipe sizing tables or sizing equations in this chapter.
(2) Sizing tables included in a listed piping system manufacturer’s installation instructions.
(3) Engineering methods. [NFPA 54:5.3.3] 1308.3.3 Allowable Pressure Drop. The design pressure loss in a piping system from the point of delivery to the inlet connection of all appliances served shall be such that the supply pressure at each appliance inlet is greater than or equal to the minimum pressure required by the appliance. [NFPA 54:5.3.4] 1308.4 Acceptable Piping Materials and Joining Methods. Materials used for piping systems shall comply with the requirements of Section 1308.4.1 through Section 1308.4.4.2.3. {NFPA 54:5.5.1.1} 1308.4.1 Used Materials. Pipe, fittings, valves, or other materials shall not be used again unless they are free of foreign materials and have been ascertained to be adequate for the service intended.
California Mechanical Code High relevance — show source text
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5California Mechanical Code High relevance — show source text
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5CMC § 207.1.1 High relevance — show source text
**
A6.207.1.1 Efficiency.
A6.207.1.2 Controls for heat pumps with supplementary electric resistance heaters.
A6.207.1.3 Thermostats.
A6.207.1.4 Gas-and oil-fired furnace standby loss controls.||
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|| |A6.207.2 Space conditioning systems.
A6.207.2.1 Supply air temperature reset controls.
A6.207.2.2 Electric resistance heating.
A6.207.2.3 Heat rejection systems.
A6.207.2.4 Hydronic system measures.
A6.207.2.5 Air distribution system duct leakage sealing.
A6.207.2.6 Variable air volume control for single zone systems.||
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|| |A6.207.3 Service water-heating systems and equipment.
A6.207.3.1 Certification by manufacturers.
A6.207.3.2 Efficiency.
A6.207.3.3 Installation.||
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|| |A6.207.4 Natural gas central furnaces, cooking equipment and pool and spa heaters.
Pilot lights prohibited.||||| |A6.207.5 Controls for space-conditioning systems.
A6.207.5.1 Thermostatic controls for each zone.
A6.207.5.2 Criteria for zonal thermostatic controls.
A6.207.5.3 Heat pump controls.
A6.207.5.4 Dampers for air supply and exhaust equipment.
A6.207.5.5 Automatic demand shed controls.||
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|| |A6.207.6 Pipe insulation.||||| |SECTION A6.209 Lighting||||| |A6.209.1 Lighting control devices, ballasts and luminaires.
A6.209.1.1 All devices: Instructions and calibration.
A6.209.1.2 Indicator lights.
**A6.209.1.3 Automatic time switch control devices.CMC § 3105F.8.1 Medium relevance — show source text
3105F.8.1 Quick release hooks. For new MOTs or berthing systems, a minimum of three quick release hooks are required for each breasting line location for tankers greater than or equal to 50,000 DWT. At least two hooks at each location shall be provided for breasting lines for tankers less than 50,000 DWT. Remote release may be considered for emergency situations.
All hooks and supporting structures shall withstand the minimum breaking load (MBL) of the strongest line with a safety factor of 1.2 or greater. Only one mooring line shall be placed on each quick release hook (N/E).
For multiple quick release hooks, the minimum horizontal load for the design of the tie-down shall be:
Equation 5-4 F d = 1.2 × MBL × [1 + 0.75 (n-1)]
where:
F d = Minimum factored demand for assembly tie-down.
n = Number of hooks on the assembly.
The capacity of the supporting structures must be larger than F d (See Section 3107F.6).
3105F.8.2 Other fittings. Other fittings include cleats, bitts and bollards.
If the allowable working loads for existing fittings are not available, the values listed in Table 31F-5-4 may be used for typical sizes, bolt patterns and layout. The allowable working loads are defined for mooring line angles up to 60 degrees from the horizontal. The combination of vertical and horizontal loads shall be considered.
TABLE 31F-5-4—ALLOWABLE WORKING LOADS Col2 Col3 Col4 TYPE OF FITTINGS NO. OF BOLTS BOLT SIZE
(in)WORKING LOAD
(kips)30 inch Cleat 4 11/8 20 42 inch Cleat 6 11/8 40 Low Bitt 10 15/8 60 per column High Bitt 10 13/4 75 per column 441/2 inch Fit. Bollard 4 13/4 70 441/2 inch Fit. Bollard 8 21/4 200 48 inch Fit. Bollard 12 23/4 450 Note:_ This table is modified from Table 6-11 of UFC 4-159-03 [5.5]_ Note:_ This table is modified from Table 6-11 of UFC 4-159-03 [5.5]_ Note:_ This table is modified from Table 6-11 of UFC 4-159-03 [5.5]_ Note:_ This table is modified from Table 6-11 of UFC 4-159-03 [5.5]_ 3105F.8.3 Base bolts. Base bolts are subjected to both shear and uplift. Forces on bolts shall be determined using the following factors:
1. Height of load application on bitts or bollards.
CMC § 1208.0 Medium relevance — show source text
1208.0 Gas Piping System Design, Materials, and Components. 1208.1 Installation of Piping System. Where required by the Authority Having Jurisdiction, a piping sketch or plan shall be prepared before proceeding with the installation. The plan shall show the proposed location of piping, the size of different branches, the various load demands, and the location of the point of delivery. [NFPA 54:5.1.1] 1208.1.1 Addition to Existing System. When additional appliances are being connected to a gas piping system, the existing piping shall be checked to determine whether it has adequate capacity. If the capacity of the system is determined to be inadequate for the additional appliances, the existing system shall be enlarged as required, or separate gas piping of adequate capacity shall be provided. [NFPA 54:5.1.2] 1208.2 Interconnections Supplying Separate Users. Where two or more meters, or two or more service regulators where meters are not provided, are located on the same premises and supply separate users, the gas piping systems shall not be interconnected on the outlet side of the meters or service regulators. [NFPA 54:5.2.1] 1208.2.1 Interconnections for Standby Fuels. Where a supplementary gas for standby use is connected downstream from a meter or a service regulator where a meter is not provided, equipment to prevent backflow shall be installed. A three-way valve installed to admit the standby supply and at the same time shut off the regular supply shall be permitted to be used for this purpose.
[NFPA 54:5.2.2.1 – 5.2.2.2] 1208.3 Sizing of Gas Piping Systems. Gas piping systems shall be of such size and so installed as to provide a supply of gas sufficient to meet the maximum demand and supply gas to each appliance inlet at not less than the minimum supply pressure required by the appliance. [NFPA 54:5.3.1]
1208.3.1 Maximum Gas Demand. The volumetric flow rate of gas to be provided shall be the sum of the maximum input of the appliances served. The volumetric flow rate of gas to be provided shall be adjusted for altitude where the installation is above 2000 feet (610 m). [NFPA 54:5.3.2.1 – 5.3.2.2] Where the input rating is not indicated, the gas supplier, appliance manufacturer, or a qualified agency shall be contacted, or the rating from Table 1208.3.1 shall be used for estimating the volumetric flow rate of gas to be supplied.
The total connected hourly load shall be used as the basis for piping sizing, assuming all appliances are operating at full capacity simultaneously.
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216 2025 CALIFORNIA PLUMBING CODE
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
FUEL GAS PIPING
the inlet connection of all appliances served shall be such that the supply pressure at each appliance inlet is greater than or equal to the minimum pressure required by the appliance. [NFPA 54:5.3.4]
1208.4 Maximum Operating Pressure in Buildings. The maximum operating pressure for any piping systems located inside buildings shall not exceed 5 psi (34 kPa) unless one or more of the following conditions are met:
(1) The piping joints are welded or brazed.
CMC § 5.1.2 Medium relevance — show source text
[ASHRAE 15:5.1.2] Double Indirect Open Spray System. A system in which the secondary substance for an indirect open spray system is heated or cooled by the secondary coolant circulated from a second enclosure. [ASHRAE 15:5.1.2.2] Indirect Closed System. A system in which a secondary coolant passes through a closed circuit in the air or other substance to be cooled or heated. [ASHRAE 15:5.1.2.3] Indirect Open Spray System. A system in which a secondary coolant is in direct contact with the air or other substance to be cooled or heated. [ASHRAE 15:5.1.2.1] Refrigeration System, Mechanical. A combination of interconnected refrigerant-containing parts constituting one closed refrigerant circuit in which a refrigerant is circulated for the purpose of extracting heat and in which a compressor(s) is/are used for compressing the refrigerant vapor.
Refrigeration System, Self-Contained. A complete factory-assembled and tested system that is shipped in one or more sections and has no refrigerant-containing parts that are joined in the field by other than companion or block valves.
Registered Design Professional. An individual who is registered or licensed by the laws of the state to perform such design work in the jurisdiction.
Relief Valve, Vacuum. A device which automatically opens or closes for relieving a vacuum with the system, depending on whether the vacuum is above or below a predetermined value.
Removable. Capable of being transferred to another location with a limited application of effort and tools. [NFPA 96:3.3.42]
Replacement Air. See Air, Makeup.
Residential Building. A building or portion thereof designed or used for human habitation.
Riser Heat Pipe. A duct that extends at an angle of 45 degrees (0.79 rad) from the horizontal. This definition shall not include any boot connection.
Room Heater. A freestanding, nonrecessed, environmental heating appliance installed in the space being heated and not connected to ducts.
Room Heater, Unvented. An unvented, self-contained, freestanding, nonrecessed, fuel gas-burning appliance for furnishing warm air by gravity or fan circulation to the space in which installed, directly from the heater without duct connection. [NFPA 54:3.3.56.6]
Rupture Member. A pressure-relief device that operates by the rupture of a diaphragm within the device on a rise to a predetermined pressure.
221.0 – S –
Seam, Welded. See Joint, Welded.
Secondary Filtration. Fume incinerators, thermal recovery units, air pollution control devices or other filtration media installed in ducts or hoods located in the path of travel of exhaust products after the initial filtration.
Self-Contained. Having all essential working parts, except energy and control connections, so contained in a case or framework that they do not depend on appliances or fastenings outside of the machine.
Service Corridor. A fully enclosed passage used for transporting hazardous production materials and purposes other than required exiting.
Service Piping. The piping and equipment between the street gas main and the gas piping system inlet that is installed by, and is under the control and maintenance of, the serving gas supplier.
CMC § 4.1.2.1 Medium relevance — show source text
[NFPA 501A:4.1.2.1 – 4.1.2.2] D 101.3 Location of Gas Supply Connection. The gas supply to the manufactured home shall be located within 4 feet (1219 mm) of the manufactured home stand. Exception: The requirement of Section D 101.3 shall not apply to gas supply connections for manufactured homes located on all-weather wood, concrete, or concrete block foundation systems or on foundations constructed in accordance with the local building code or, in the absence of a local code, with a recognized model building code. [NFPA 501A:4.1.3] D 101.4 Recreational Vehicle Park Fuel-Gas Equip- ment and Installations. Fuel gas equipment and installations shall comply with this appendix, except as otherwise permitted or required by this code.
D 102.0 Single and Multiple Manufactured Home Site Fuel Supply Systems. D 102.1 Underground Installation. Underground gas piping system installations shall comply with any applicable building code and Section D 102.1.1 and Section D 102.1.2.
[NFPA 501A:4.2.1] D 102.1.1 Open-Ended Gastight Conduit. Underground gas piping shall not be installed beneath that portion of a manufactured home site reserved for the
location of a manufactured home or manufactured home accessory building or structure unless installed in the open-ended gastight conduit of Section D 102.1.2.
[NFPA 501A:4.2.1.1] D 102.1.2 Requirements. The open-ended gastight conduit shall conform to the requirements in the following: (1) The conduit shall be not less than Schedule 40 pipe that is approved for underground installation beneath buildings. (2) The interior diameter of the conduit shall be not less than [1] ⁄ 2 of an inch (15 mm) larger than the outside diameter of the gas piping.
(3) The conduit shall extend to a point not less than 4 inches (102 mm) beyond the outside wall of the manufactured home or accessory building or structure, and the outer ends shall not be sealed.
(4) Where the conduit terminates within a manufactured home or accessory building or structure, it shall be accessible and the space between the conduit and the gas piping shall be sealed to prevent leakage of gas into the building. [NFPA 501A:4.2.1.2 – 4.2.1.2.4]
D 103.0 Manufactured Home Site Gas Shutoff Valve.
D 103.1 General. Gas shutoff valves shall conform to Section D 103.2, except for manufactured homes located on foundations constructed in accordance with the local building code or, in the absence of a local code, with a recognized model building code. [NFPA 501A:4.2.2] D 103.2 Shutoff Valve Location. Each manufactured home site shall have a listed gas shutoff valve installed upstream of the manufactured home site gas outlet. The gas shutoff valve shall be located on the outlet riser at a height of not less than 6 inches (152 mm) above grade. A gas shutoff valve shall not be located under any manufactured home. The outlet shall be equipped with a cap or plug to prevent discharge of gas whenever the manufactured home site outlet is not connected to a manufactured home.
CMC § 5.3.2.3 Medium relevance — show source text
The total connected hourly load shall be used as the basis for piping sizing, assuming all appliances are operating at full capacity simultaneously. Exception: Sizing shall be permitted to be based upon established load diversity factors. [NFPA 54:5.3.2.3] 1308.3.2 Sizing Methods. Gas piping shall be sized in accordance with one of the following: (1) Pipe sizing tables or sizing equations in this chapter.
(2) Sizing tables included in a listed piping system manufacturer’s installation instructions.
(3) Engineering methods. [NFPA 54:5.3.3] 1308.3.3 Allowable Pressure Drop. The design pressure loss in a piping system from the point of delivery to the inlet connection of all appliances served shall be such that the supply pressure at each appliance inlet is greater than or equal to the minimum pressure required by the appliance. [NFPA 54:5.3.4] 1308.4 Acceptable Piping Materials and Joining Methods. Materials used for piping systems shall comply with the requirements of Section 1308.4.1 through Section 1308.4.4.2.3. {NFPA 54:5.5.1.1} 1308.4.1 Used Materials. Pipe, fittings, valves, or other materials shall not be used again unless they are free of foreign materials and have been ascertained to be adequate for the service intended. [NFPA 54:5.5.1.2] 1308.4.2 Metallic Pipe. Metallic pipe shall be in accordance with Section 1308.4.2.1 through Section 1308.4.2.4.
1308.4.2.1 Cast Iron. Cast-iron pipe shall not be used. [NFPA 54:5.5.2.1] 1308.4.2.2 Steel, Stainless Steel, and Wrought-Iron. Steel, stainless steel, and wroughtiron pipe shall be at least Schedule 40 and shall comply with the dimensional standards of ASME B36.10M and one of the following: (1) ASTM A53 (2) ASTM A106 (3) ASTM A312 {NFPA 54:5.5.2.2}
TABLE 1308.3.1
APPROXIMATE GAS INPUT FOR TYPICAL APPLIANCES
[NFPA 54: TABLE A.5.3.2.1]
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2025 CALIFORNIA MECHANICAL CODE 277
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
FUEL GAS PIPING
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1308.4.3 Metallic Tubing. Tubing shall not be used with gases corrosive to the tubing material. [NFPA 54:5.5.3.1] 1308.4.3.1 Steel Tubing. Steel tubing shall comply with ASTM A254. [NFPA 54:5.5.3.2] **1308.4.3.2 Stainless Steel Tubing.
CMC § 0.293 Medium relevance — show source text
automatic storage
30 to 40 gallon tank
Water heater, automatic storage
50 gallon tank
Water heater, automatic instantaneous
Capacity at 2 gallons per minute
Capacity at 4 gallons per minute
Capacity at 6 gallons per minute
Water heater, domestic, circulating or
side-arm|
35 000
50 000
142 800
285 000
428 400
35 000| |
Cooking Appliances
Range, freestanding, domestic
Built-in oven or broiler unit, domestic
Built-in top unit, domestic|
65 000
25 000
40 000| |
Other Appliances
Refrigerator
Clothes dryer, Type 1 (domestic)
Gas fireplace direct-vent
Gas log
Barbecue
Gaslight|
3000
35 000
40 000
80 000
40 000
2500|For SI units: 1000 British thermal units per hour = 0.293 kW
1208.3.2 Sizing Methods. Gas piping shall be sized in accordance with one of the following:
(1) Pipe sizing tables or sizing equations in this chap ter.
(2) Sizing tables included in a listed piping system manufacturer’s installation instructions.
(3) Engineering methods. [NFPA 54:5.3.3]
1208.3.3 Allowable Pressure Drop. The design pressure loss in a piping system from the point of delivery to
TABLE 1208.3.1
APPROXIMATE GAS INPUT FOR
TYPICAL APPLIANCES
[NFPA 54: TABLE A.5.3.2.1]
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For SI units: 1000 British thermal units per hour = 0.293 kW
2025 CALIFORNIA PLUMBING CODE 217
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
FUEL GAS PIPING
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1208.5.4 Plastic Pipe, Tubing, and Fittings. Polyethylene plastic pipe, tubing, and fittings used to supply fuel gas shall conform to ASTM D2513. Pipe to be used shall be marked “gas” and “ASTM D2513.” Polyamide pipe, tubing, and fittings shall be identified in and conform to ASTM F2945. Pipe to be used shall be marked “gas” and “ASTM F2945.” Polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC) plastic pipe, tubing, and fittings shall not be used to supply fuel gas. [NFPA 54:5.5.4.1.1 – 5.5.4.1.3]
1208.5.5 Regulator Vent Piping. Plastic pipe and fittings used to connect regulator vents to remote vent terminations shall be PVC (Schedule 40 and 80). PVC vent piping shall not be installed indoors. {NFPA 54:5.5.4.2}
Frequently asked questions
How do I know when to use Table 1308.3.1 versus the manufacturer’s data?
Use Table 1308.3.1 only when the appliance input rating is not indicated; otherwise use the appliance manufacturer’s rated input. The code explicitly allows Table 1308.3.1 for estimating unknown inputs.
Do I always assume all appliances run at once?
Yes — the code’s default is to size for the total connected hourly load assuming simultaneous operation unless you apply an approved load diversity factor (the exception in § 1308.3.1).
What does “adjust for altitude” mean in practice?
The code requires an altitude adjustment above 2,000 ft (610 m) (§ 1308.3.1), but it does not give a single universal multiplier in that paragraph; you must apply the chapter’s sizing equations and correction factors (Cr/Y or engineering methods) or use manufacturer data that account for altitude.
Where do I get the Btu per cubic foot value to convert inputs to ft3/h?
Obtain the local average Btu/ft3 heating value from the serving gas supplier and use it to convert appliance Btu/h to ft3/h as required by the fuel‑gas sizing guidance in the chapter.
Can I use a listed CSST or manufacturer’s system table instead of the code tables?
Yes — § 1308.3.2 permits use of sizing tables included in a listed piping system manufacturer’s instructions in lieu of the chapter tables or equations.
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