CMC · California Mechanical Code

What plumbing connection and backflow protections apply to mechanical equipment?

Q: Is an air gap ever acceptable for mechanical equipment?

Yes — an approved air gap can be acceptable for many inlets (tanks, sumps, pools) where an open discharge prevents backflow. Air gaps must meet the minimum dimensions in the CPC (Table 603.3.1) or be part of a listed assembly .

Q: When is a reduced‑pressure (RP) assembly mandatory?

When the system can create backpressure (pumps, booster pumps) or when chemicals or other high‑hazard contaminants can enter the water (chemical injectors, antifreeze), the CPC requires an RP (see § 603.5.6.1 and § 603.5.6.3 ) .

If mechanical equipment connects to potable water and can create backsiphonage or backpressure (pumps, boilers, chemical injection, water‑cooled equipment), the California Plumbing Code requires an approved backflow prevention method (air gap, vacuum breaker, double‑check, or reduced‑pressure assembly depending on the hazard). The uploaded California Mechanical Code files did not contain the exact text of **§ 312.0** or **§ 312.1**, so device selection and testing rules are cited from the CPC (**§ 602.0**, **§ 603.0** and subparts, Table 603.2) ; the Mechanical Code file shows Chapter 312 heading (fuel gas piping) but the specific sections requested were not available in the provided CMC files .

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Last reviewed: July 6, 2026

What the code requires

Mechanical Code sections § 312.0 and § 312.1 requested by the user were not found in the uploaded California Mechanical Code (CMC) files (the Mechanical Code copy in the files shows the Chapter 312 heading for fuel gas piping but the specific text of § 312.0 / § 312.1 was not available) . Because the CMC text for those exact sections is not present in the provided files, I cannot quote or summarize those specific CMC paragraphs.

Where potable-water connections to mechanical equipment are concerned, the applicable requirements for backflow prevention are contained in the California Plumbing Code (CPC) — specifically the cross‑connection / backflow provisions in § 603.0 and its subparts and the unlawful‑connection rules in § 602.0. For example, the CPC requires cross‑connection control for any water‑operated equipment that can contaminate or cause backflow into the potable supply, and it lists device choices and application rules (air gap, AVB, PVB, DC, RP, etc.) in Chapter 6, Table 603.2 and sections § 603.3 / § 603.5 .

The single most important point: any mechanical equipment that can cause backsiphonage or backpressure to the potable system must be protected with an approved backflow prevention method — follow the CPC cross‑connection rules (Chapter 6) for the device selection and installation requirements (e.g., § 603.0, Table 603.2) .

Requirements in detail

Scope & applicability (what kinds of mechanical equipment)

Any equipment connected to the potable water supply that can contaminate or return water (used water, cooling water, chemical‑treated fluids, boiler water, etc.) is within cross‑connection control per § 602.0 and § 603.0 of the CPC .
The CPC explicitly calls out: water‑cooled equipment (compressors, degreasers, etc.), steam/hot water boilers, chemical injectors, and many equipment‑mounted inlets as requiring backflow protection (see § 603.5.8, § 603.5.10, § 603.5.6.3) .

Types of protection required — decision table

The code choice depends on the degree of hazard (pollution vs contamination) and on whether backpressure or backsiphonage is possible. Use Table 603.2 to select the device. Key practical rules are summarized below.

Equipment / situation	Degree of hazard	Typical required protection	Code Reference
Water‑cooled compressors, chillers, degreasers	Potential contamination or backpressure (depends on fluid)	Backflow preventer suitable to degree of hazard (double check or reduced‑pressure where chemical/backpressure present)	§ 603.5.8, Table 603.2
Potable supply to steam/hot‑water boilers	Often contamination if treatment chemicals present	Double check assembly, RP (reduced‑pressure) or backflow preventer with intermediate vent + PRV; RP required when chemicals introduced
Irrigation / sprinklers with pumps or chemical injection	Backpressure possible; chemicals	Reduced‑pressure principle (RP) (mandatory with pumps/chemical injectors)
Tanks, vats, sumps, pool fill lines	Backsiphonage risk	Approved air gap or listed vacuum breaker or appropriate backflow assembly per Table 603.2
Hose‑end outlets on mechanical equipment	Backsiphonage risk	Non‑removable hose bibb backflow preventer, hose vacuum breaker, or AVB ≥ 6 in above usage point (critical level)

(For exact device selection, consult Table 603.2 in the CPC and the specific sub‑sections § 603.3–§ 603.5 for device definitions and permitted uses) .

Installation & maintenance highlights

Devices must be approved by the Authority Having Jurisdiction and be tested to accepted standards; installations must follow the device listing instructions (§ 603.2, § 603.4) .
Backflow assemblies must be tested at installation and at least annually thereafter, or more often if the AHJ requires, by a certified tester (per CPC) .
Air‑gaps must meet the minimum distances in Table 603.3.1 (air‑gap sizing) and device‑mounted vacuum breakers must be installed at their listed critical level .

How to decide between DC (double check) and RP (reduced pressure)

Use RP (reduced‑pressure principle assembly) for high‑hazard contamination (toxic chemicals, health hazards) or systems capable of creating backpressure (pumps, chemical injectors) — the CPC requires RP in those cases (see § 603.5.6.1, § 603.5.6.3) .
Double check (DC) assemblies may be acceptable for lower‑hazard situations where there is no chemical injection and the hazard is pollution rather than contamination; check Table 603.2 for each application .

Exceptions & special cases

If the mechanical equipment discharges only to an open atmospheric receiver and cannot generate backpressure or draw return water, an air gap may be acceptable in lieu of a mechanical assembly; follow air gap sizing rules in Table 603.3.1 .
Where the plumbing code allows specific alternatives (equipment‑mounted, listed vacuum breakers, or special ASSE/IAPMO listed devices) use the device in accordance with its listing and manufacturer’s instructions (§ 603.5.13) .
For fire‑protection systems, special rules apply (hydraulic considerations, antifreeze/chemicals require RP) — see the CPC fire‑system cross‑connection subsections (§ 603.5.14 et seq.) .

If you need a CMC‑only quote for § 312.0 / § 312.1, I cannot provide it because those specific paragraphs were not present in the uploaded CMC files; the CMC file only shows the chapter heading for 312 (Fuel Gas Piping) in the available copy .

Common mistakes

Assuming mechanical code covers potable‑water backflow for equipment — in California the CPC (Plumbing Code) contains the cross‑connection/backflow rules that apply to water connections on mechanical equipment (see § 603.0) .
Installing the wrong device for the degree of hazard (e.g., installing a DC when chemicals or pumps require an RP) — check Table 603.2 and § 603.5 subitems before finalizing device selection .
Forgetting annual testing and certification requirements — assemblies must be tested at installation and at least annually by a certified tester (§ 603.2, testing requirements) .
Mounting a vacuum breaker at the wrong height — many vacuum breaker listings require a minimum critical level (for example, 1 in for some deck‑mounts, 6 in for others) — follow § 603.3.1 / § 603.5.13 and device listing .

Worked example

Scenario: A rooftop packaged chiller uses potable water for cooling condenser tubes. The chiller has a booster pump on the condenser water side and glycol may be introduced seasonally for freeze protection.

Hazard analysis: Because a pump and chemical (glycol) are present, the system can create backpressure and introduces a chemical contamination hazard.
Code requirement: The CPC requires protection where pumps or chemical injectors are present — RP (reduced‑pressure principle backflow prevention assembly) is required in this scenario per § 603.5.6.1 and § 603.5.6.3 (systems with pumps / chemical injectors) and Table 603.2 .
Installation steps (high level):
- Specify a listed RP assembly sized for the chiller inlet flow and the system pressures.
- Install the RP on the potable supply to the chiller upstream of any shutoff valves in accordance with the manufacturer and CPC installation requirements (§ 603.4) .
- Provide space for testing (isolation valves, test cocks) and arrange for the assembly to be tested at installation and annually by a certified tester (§ 603.2) .

Numeric illustration: if the chiller makes a nominal inlet demand of 50 gpm, select an RP rated above that flow and ensure pressure drop through the RP is accounted for in the chiller’s inlet pressure calculations (the CPC notes hydraulic effects must be considered where backflow devices are installed in fire or pressurized systems; similar prudence applies to mechanical service connections) .

Related provisions (CMC / CPC)

California Plumbing Code — § 602.0 (Unlawful connections / cross‑contamination) .
California Plumbing Code — § 603.0 (Cross‑connection control; device approval / Table 603.2) .
California Plumbing Code — § 603.3 through § 603.5 (Definitions of devices and application rules; equipment‑specific subsections such as § 603.5.8 for water‑cooled equipment and § 603.5.10 for boilers) .
California Mechanical Code — Chapter heading § 312 (Fuel gas piping) — available in the Mechanical Code file but the specific § 312.0 / § 312.1 text was not present in the uploaded Mechanical Code files; see chapter heading in the provided CMC file .
California Mechanical Code — refrigeration / machinery room provisions (example relevant CMC sections: § 1106.11 series for refrigerating machinery rooms) — mechanical code text present in uploaded files (useful when mechanical equipment contains refrigerants or special room conditions) .

Code references

Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:

CMC § 302.2 High relevance — show source text
E 302.2 Water Service Outlet. Each manufactured home lot shall be provided with a water service outlet delivering potable water. The water service outlet riser shall be not less than [3] ⁄ 4 of an inch (20 mm) nominal pipe size and capable of delivering 12 water supply fixture units.

E 302.2.1 Connection. A manufactured home shall be connected to the park water service outlet by a flexible connector, such as copper or copper alloy or other approved material not less than [3] ⁄ 4 of an inch nominal (20 mm) interior diameter.

E 302.2.2 Water Supply Fixture Units. Park water distribution systems shall be designed to deliver a minimum of 12 water supply fixture units to each lot and installed with materials in accordance with Chapter 6, Appendix A, or both of this code.

E 302.2.3 Pressure. Each manufactured home park water distribution system shall be so designed and maintained as to provide a pressure of not less than 20 poundsforce per square inch (psi) (138 kPa) at each manufactured home lot at maximum operating conditions.

E 302.2.4 Location. Each lot water service outlet shall be located in the third rear section and within 4 feet (1219 mm) of the proposed location of the manufactured home.

E 302.3 Shutoff Valve. A separate water shutoff valve shall be installed in each water service outlet at each manufactured home lot. Where a listed backflow protective device is installed, the service shutoff shall be located on the supply side of such device.

E 302.4 Backflow Preventer. Where a condition exists in the plumbing of a manufactured home that creates a crossconnection, a listed backflow preventer shall be installed in the water service line to the manufactured home at or near the

water service outlet. Where a hose bibb or outlet is installed on the supply outlet riser in addition to the service connector, a listed backflow preventer shall be installed on each additional outlet.

E 302.5 Pressure-Relief Valve. Where it is required to install a backflow preventer at the manufactured home lot service outlet, a listed pressure-relief valve shall be installed in the water service line on the discharge side of the backflow preventer. Pressure-relief valves shall be set to release at a pressure at a maximum of 150 psi (1034 kPa). Pressurerelief valves shall discharge toward the ground. Backflow preventers and pressure-relief valves shall be not less than 12 inches (305 mm) above the ground.

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APPENDIX E

E 302.6 Mechanical Protection. Park water service out lets, backflow preventers, and pressure-relief valves shall be protected from damage by vehicles or other causes. Such protection shall be permitted to consist of posts, fencing, or other permanent barriers.

E 302.7 Water-Conditioning Equipment. A permit shall be obtained from the Authority Having Jurisdiction before installing water-conditioning equipment on a manufactured home lot. Approval of the park operator is required on applications for a permit to install such equipment. Where the water-conditioning equipment is of the regenerating type, and the park drainage system discharges into a public sewer, approval of the sanitary district or agency having jurisdiction over the public sewer is required.

CMC § 603.5.6.1 High relevance — show source text

(1) Atmospheric vacuum breaker (AVB)

(2) Pressure vacuum breaker backflow prevention assembly (PVB)

(3) Spill-resistant pressure vacuum breaker (SVB)

(4) Reduced-pressure principle backflow prevention assembly (RP)

(5) A valve complying with IAPMO PS 72 603.5.6.1 Systems with Pumps. Where sprinkler and irrigation systems have pumps, connections for pumping equipment, or auxiliary air tanks, or are otherwise capable of creating backpressure, the potable water supply shall be protected by the following type of device where the backflow device is located upstream from the source of backpressure:

(1) Reduced-pressure principle backflow prevention assembly (RP) 603.5.6.2 Systems with Backflow Devices. Where systems have a backflow device installed downstream from a potable water supply pump or a potable water supply pump connection, the device shall be one of the following:

(1) Atmospheric vacuum breaker (AVB)

(2) Pressure vacuum breaker backflow prevention assembly (PVB)

(3) Spill-resistant pressure vacuum breaker (SVB)

(4) Reduced-pressure principle backflow prevention assembly (RP) 603.5.6.3 Systems with Chemical Injectors. Where systems include a chemical injector or provisions for chemical injection, the potable water supply shall be protected by a reduced-pressure principle backflow prevention assembly (RP).

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WATER SUPPLY AND DISTRIBUTION

TABLE 603.2 BACKFLOW PREVENTION DEVICES, ASSEMBLIES, AND METHODS	Col2	Col3	Col4	Col5	Col6	Col7
DEGREE OF HAZARD	DEGREE OF HAZARD	DEGREE OF HAZARD	DEGREE OF HAZARD	DEGREE OF HAZARD	DEGREE OF HAZARD	DEGREE OF HAZARD
DEVICE, ASSEMBLY, OR METHOD1	APPLICABLE STANDARDS	POLLUTION (LOW HAZARD)	POLLUTION (LOW HAZARD)	CONTAMINATION (HIGH HAZARD)	CONTAMINATION (HIGH HAZARD)	INSTALLATION2,3
DEVICE, ASSEMBLY, OR METHOD1	APPLICABLE STANDARDS	BACK- SIPHONAGE	BACK- PRESSURE	BACK- SIPHONAGE	BACK- PRESSURE	BACK- PRESSURE
Air gap	ASME A112.1.2	X	––	X	––	See Table 603.3.1 in this chapter.
Air gap fittings for use with plumbing fixtures, appliances, and appurte- nances	ASME A112.1.3	X	––	X	––	Air gap fitting is a device with an internal air gap, and typical installation includes plumbing fixtures, appliances,

CMC § 603.2 High relevance — show source text

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REFERENCED STANDARDS

TABLE 1701.1 (continued) REFERENCED STANDARDS

STANDARD NUMBER	STANDARD TITLE	APPLICATION	REFERENCED SECTION
ASSE 1012-2009	Backflow Preventers with an Intermediate Atmospheric Vent	Backflow Protection	Table 603.2
ASSE 1013-2021	Reduced Pressure Principle Backflow Prevention Assemblies	Backflow Protection	Table 603.2
ASSE 1014-2020	Backflow Prevention Devices for Hand-Held Showers	Backflow Protection	417.3
ASSE 1015-2021	Double Check Backflow Prevention	Backflow Protection	Table 603.2
ASSE 1016-2017/ASME A112.1016-2017/CSA B125.16-2017	Automatic Compensating Valves for Individual Showers and Tub/Shower Combinations	Valves	408.4, 408.4.2(1)
ASSE 1018-2001 (R2021)	Trap Seal Primer Valves - Potable Water Supplied	Valves	1007.2
ASSE 1019-2011 (R2016)	Wall Hydrant with Backflow Protection and Freeze Resistance	Backflow Protection	Table 603.2
ASSE 1020-2020	Pressure Vacuum Breaker Assemblies	Backflow Protection	Table 603.2
ASSE 1022-2021	Backflow Preventer for Beverage Dispensing Equipment	Backflow Protection	Table 603.2, 603.5.12
ASSE 1023-2020	Electrically Heated or Cooled Water Dispensers	Appliances	417.6
ASSE 1024-2017 (R2021)	Dual Check Backflow Preventers	Backflow Protection	Table 603.2, 603.5.12
ASSE 1032-2004 (R2021)	Dual Check Valve Type Backflow Preventers for Carbonated Beverage Dispensers, Post Mix Type	Backflow Protection	603.5.12
ASSE 1035-2020	Laboratory Faucet Backflow Preventers	Backflow Protection	Table 603.2, 603.3.11
ASSE 1037-2020/ASME A112.1037-2020/CSA B125.37-2020	Pressurized Flushing Devices for Plumbing Fixtures	Backflow Protection	413.2
ASSE 1044-2015 (R2020)	Trap Seal Primer - Drainage Types and Electric Design Types	DWV Components	1007.

CMC § 602.4 High relevance — show source text
602.4 Approval by Authority. No water piping supplied by a private water supply system shall be connected to any other source of supply without the approval of the Authority Having Jurisdiction, Health Department, or other department having jurisdiction.

603.0 Cross-Connection Control.

603.1 General. Cross-connection control shall be provided in accordance with the provisions of this chapter.

No person shall install a water-operated equipment or mechanism, or use a water-treating chemical or substance, where it is found that such equipment, mechanism, chemical, or substance causes pollution or contamination of the domestic water supply. Such equipment or mechanism shall be permitted where equipped with an approved backflow prevention device or assembly.

603.2 Approval of Devices or Assemblies. Before a device or an assembly is installed for the prevention of backflow, it shall have first been approved by the Authority Having Jurisdiction. Devices or assemblies shall be tested in accordance with recognized standards or other standards acceptable to the Authority Having Jurisdiction. Backflow prevention devices and assemblies shall comply with Table 603.2, except for specific applications and provisions as stated in Section 603.5.1 through Section 603.5.22.

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WATER SUPPLY AND DISTRIBUTION

Devices or assemblies installed in a potable water supply system for protection against backflow shall be maintained in good working condition by the person or persons having control of such devices or assemblies. Such devices or assemblies shall be tested at the time of installation, repair, or relocation and not less than on an annual schedule thereafter, or more often where required by the Authority Having Jurisdiction. Where found to be defective or inoperative, the device or assembly shall be repaired or replaced. No device or assembly shall be removed from use or relocated or other device or assembly substituted, without the approval of the Authority Having Jurisdiction.

Testing or maintenance shall be performed by a certified backflow assembly tester or repairer certified in accordance with ASSE/IAPMO/ANSI Series 5000 or any other additional certification approved by the Authority Having Jurisdiction.

603.3 Backflow Prevention Devices, Assemblies, and Methods. Backflow prevention devices, assemblies, and methods shall comply with Section 603.3.1 through Section 603.3.12.

603.3.1 Air Gap. The minimum air gap to afford backflow protection shall be in accordance with Table 603.3.1. 603.3.2 Atmospheric Vacuum Breaker (AVB). An atmospheric vacuum breaker consists of a body, a checking member, and an atmospheric port.

603.3.3 Hose Connection Backflow Preventer. A hose connection backflow preventer consists of two independent check valves with an independent atmospheric vent between and a means of field testing and draining.

603.3.4 Double Check Valve Backflow Prevention Assembly (DC). A double check valve backflow prevention assembly consists of two independently acting internally loaded check valves, four properly located test cocks, and two isolation valves.

603.3.5 Pressure Vacuum Breaker Backflow Pre- vention Assembly (PVB). A pressure vacuum breaker backflow prevention assembly consists of a loaded air inlet valve, an internally loaded check valve, two properly located test cocks, and two isolation valves.
CMC § 603.5.2 High relevance — show source text
603.5.2 Ballcock. Water closet and urinal tanks shall be equipped with a ballcock. The ballcock shall be installed with the critical level not less than 1 inch (25.4 mm) above the full opening of the overflow pipe. In cases where the ballcock has no hush tube, the bottom of the water supply inlet shall be installed 1 inch (25.4 mm) above the full opening of the overflow pipe.

603.5.3 Backflow Prevention. Water closet flushometer tanks shall be protected against backflow by an approved backflow prevention assembly, device, or method.

603.5.4 Heat Exchangers. Heat exchangers used for heat transfer, heat recovery, or solar heating shall protect the potable water system from being contaminated by the

heat-transfer medium. Single-wall heat exchangers used in indirect-fired water heaters shall meet the requirements of Section 505.4.1. Double-wall heat exchangers shall separate the potable water from the heat-transfer medium by providing a space between the two walls that are vented to the atmosphere. 603.5.5 Water Supply Inlets. Water supply inlets to tanks, vats, sumps, swimming pools, and other receptors shall be protected by one of the following means:

(1) An approved air gap.

(2) A listed vacuum breaker installed on the discharge side of the last valve with the critical level not less than 6 inches (152 mm) or in accordance with its listing.

(3) A backflow preventer suitable for the degree of hazard, installed in accordance with the requirements for that type of device or assembly as set forth in this chapter. 603.5.6 Protection from Lawn Sprinklers and Irri- gation Systems. Potable water supplies to systems having no pumps or connections for pumping equipment, and no chemical injection or provisions for chemical injection, shall be protected from backflow by one of the following devices:

(1) Atmospheric vacuum breaker (AVB)

(2) Pressure vacuum breaker backflow prevention assembly (PVB)

(3) Spill-resistant pressure vacuum breaker (SVB)

(4) Reduced-pressure principle backflow prevention assembly (RP)

(5) A valve complying with IAPMO PS 72 603.5.6.1 Systems with Pumps. Where sprinkler and irrigation systems have pumps, connections for pumping equipment, or auxiliary air tanks, or are otherwise capable of creating backpressure, the potable water supply shall be protected by the following type of device where the backflow device is located upstream from the source of backpressure:

(1) Reduced-pressure principle backflow prevention assembly (RP) 603.5.6.2 Systems with Backflow Devices. Where systems have a backflow device installed downstream from a potable water supply pump or a potable water supply pump connection, the device shall be one of the following:

(1) Atmospheric vacuum breaker (AVB)

(2) Pressure vacuum breaker backflow prevention assembly (PVB)

(3) Spill-resistant pressure vacuum breaker (SVB)

(4) Reduced-pressure principle backflow prevention assembly (RP) 603.5.6.3 Systems with Chemical Injectors. Where systems include a chemical injector or provisions for chemical injection, the potable water supply shall be protected by a reduced-pressure principle backflow prevention assembly (RP).

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CMC § 602.0 High relevance — show source text
602.0 Unlawful Connections.

602.1 Prohibited Installation. No installation of potable water supply piping, or part thereof, shall be made in such a manner that it will be possible for used, unclean, polluted, or contaminated water, mixtures, or substances to enter a portion of such piping from a tank, receptor, equipment, or plumbing fixture by reason of backsiphonage, suction, or other cause, either during normal use and operation thereof, or where such tank, receptor, equipment, or plumbing fixture is flooded or subject to pressure exceeding the operating pressure in the hot or cold water piping. 602.2 Cross-Contamination. No person shall make a connection or allow one to exist between pipes or conduits carrying domestic water supplied by a public or private building supply system, and pipes, conduits, or fixtures containing or carrying water from any other source or containing or carrying water that has been used for any purpose whatsoever, or piping carrying chemicals, liquids, gases, or substances whatsoever, unless there is provided a backflow prevention device approved for the potential hazard and maintained in accordance with this code. Each point of use shall be separately protected where potential cross-contamination of individual units exists.

602.3 Backflow Prevention. No plumbing fixture, device, or construction shall be installed or maintained, or shall be connected to a domestic water supply, where such installation or connection provides a possibility of polluting such water supply or cross-connection between a distributing system of water for drinking and domestic purposes and water that becomes contaminated by such plumbing fixture, device, or construction unless there is provided a backflow prevention device approved for the potential hazard.

602.4 Approval by Authority. No water piping supplied by a private water supply system shall be connected to any other source of supply without the approval of the Authority Having Jurisdiction, Health Department, or other department having jurisdiction.

603.0 Cross-Connection Control.

603.1 General. Cross-connection control shall be provided in accordance with the provisions of this chapter.

No person shall install a water-operated equipment or mechanism, or use a water-treating chemical or substance, where it is found that such equipment, mechanism, chemical, or substance causes pollution or contamination of the domestic water supply. Such equipment or mechanism shall be permitted where equipped with an approved backflow prevention device or assembly.

603.2 Approval of Devices or Assemblies. Before a device or an assembly is installed for the prevention of backflow, it shall have first been approved by the Authority Having Jurisdiction. Devices or assemblies shall be tested in accordance with recognized standards or other standards acceptable to the Authority Having Jurisdiction. Backflow prevention devices and assemblies shall comply with Table 603.2, except for specific applications and provisions as stated in Section 603.5.1 through Section 603.5.22.

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WATER SUPPLY AND DISTRIBUTION
CMC § 603.5.9 High relevance — show source text
603.5.9 Aspirators. Water inlets to water-supplied aspirators shall be equipped with a vacuum breaker installed in accordance with its listing requirements and this chapter. The discharge shall drain through an air gap. Where the tailpiece of a fixture to receive the discharge of an aspirator is used, the air gap shall be located above the flood-level rim of the fixture.

603.5.10 Steam or Hot Water Boilers. Potable water connections to steam or hot water boilers shall be protected from backflow by a double check valve backflow prevention assembly, backflow preventer with intermediate atmospheric vent and pressure reducing valve, or reduced pressure principle backflow prevention assembly in accordance with Table 603.2. Where chemicals are introduced into the system a reduced pressure principle backflow prevention assembly shall be provided in accordance with Table 603.2.

603.5.11 Nonpotable Water Piping. In cases where it is impractical to correct individual cross-connections on the domestic waterline, the line supplying such outlets

shall be considered a nonpotable water line. No drinking or domestic water outlets shall be connected to the nonpotable waterline. Where possible, portions of the nonpotable waterline shall be exposed, and exposed portions shall be properly identified in a manner satisfactory to the Authority Having Jurisdiction. Each outlet on the nonpotable waterline that is permitted to be used for drinking or domestic purposes shall be posted: “CAUTION: NONPOTABLE WATER, DO NOT DRINK.”

[HCD 1 & HCD 2] An international symbol of a glass in a circle with a slash through it shall be provided sim- ilar to that shown in Figure 601.

603.5.12 Beverage Dispensers. Potable water supply to carbonated beverage dispensers shall be protected by an air gap or a vented backflow preventer that complies with ASSE 1022. For carbonated beverage dispensers, piping material installed downstream of the backflow preventer shall not be affected by carbon dioxide gas. Non-carbonated beverage dispensers, such as ice makers and coffee machines, shall be protected by an air gap or dual check backflow preventer that comply with ASSE 1032 or ASSE 1024.

603.5.13 Deck-Mounted and Equipment- Mounted Vacuum Breakers. Deck-mounted or equipment-mounted vacuum breakers shall be installed in accordance with their listing and the manufacturer’s installation instructions, with the critical level not less than 1 inch (25.4 mm) above the flood-level rim.

603.5.14 Protection from Fire Systems.

Note: Fire Protection Systems has not been adopted by the State Fire Marshal. This section cannot be adopted or enforced pursuant to California Health and Safety Code 13114.7(a), which is being cited for reference. California Health and Safety Code 13114.7.

(a) For the purposes of this section the following are definitions of class I and class II systems:

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WATER SUPPLY AND DISTRIBUTION
CMC § 302.5 High relevance — show source text
water service outlet. Where a hose bibb or outlet is installed on the supply outlet riser in addition to the service connector, a listed backflow preventer shall be installed on each additional outlet.

E 302.5 Pressure-Relief Valve. Where it is required to install a backflow preventer at the manufactured home lot service outlet, a listed pressure-relief valve shall be installed in the water service line on the discharge side of the backflow preventer. Pressure-relief valves shall be set to release at a pressure at a maximum of 150 psi (1034 kPa). Pressurerelief valves shall discharge toward the ground. Backflow preventers and pressure-relief valves shall be not less than 12 inches (305 mm) above the ground.

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APPENDIX E

E 302.6 Mechanical Protection. Park water service out lets, backflow preventers, and pressure-relief valves shall be protected from damage by vehicles or other causes. Such protection shall be permitted to consist of posts, fencing, or other permanent barriers.

E 302.7 Water-Conditioning Equipment. A permit shall be obtained from the Authority Having Jurisdiction before installing water-conditioning equipment on a manufactured home lot. Approval of the park operator is required on applications for a permit to install such equipment. Where the water-conditioning equipment is of the regenerating type, and the park drainage system discharges into a public sewer, approval of the sanitary district or agency having jurisdiction over the public sewer is required.

E 302.7.1 Approval. Regenerating water-conditioning equipment shall be listed and labeled by an approved listing agency.

E 302.7.2 Installation. Regenerating units shall discharge the effluent of regeneration into a trap not less than 1 [1] ⁄ 2 inches (40 mm) in diameter connected to the manufactured home park drainage system. An approved air gap shall be installed on the discharge line a minimum of 12 inches (305 mm) above the ground.

E 302.8 Testing. Installations shall be tested and inspected in accordance with Chapter 3 of this code.

E 401.0 Fuel Supply.

E 401.1 Fuel Gas Piping Systems. All fuel gas piping systems serving manufactured homes, accessory buildings, or structures and communities shall be designed and constructed in accordance with any applicable provisions of NFPA 54 and NFPA 58. NFPA 31 shall apply to oil fuel-burning systems and shall conform to the criteria of the Authority Having Jurisdiction. [NFPA 501A:4.1.1.1 – 4.1.1.2]

E 401.2 Gas Supply Connections. Gas supply connections at sites, where provided from an underground gas supply piping system, shall be located and arranged to permit attachment to a manufactured home occupying the site.

For the installation of liquefied petroleum gas (LP-Gas) storage systems, the provisions of NFPA 58 shall be followed. [NFPA 501A:4.1.2.1 – 4.1.2.2]

E 401.3 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.
CMC § 25.4 High relevance — show source text
2 Vertical walls, ribs, or similar obstructions extending from the water surface to or above the horizontal plane of the spout opening other than specified in Footnote 1 above. The effect of three or more such vertical walls or ribs has not been determined. In such cases, the air gap shall be measured from the top of the wall. 3 The effective opening shall be the minimum cross-sectional area at the seat of the control valve or the supply pipe or tubing that feeds the device or outlet. Where two or more lines supply one outlet, the effective opening shall be the sum of the cross-sectional areas of the individual supply lines or the area of the single outlet, whichever is smaller. 4 Air gaps less than 1 inch (25.4 mm) shall be approved as a permanent part of a listed assembly that has been tested under actual backflow conditions with vacuums of 0 to 25 inches of mercury (85 kPa).

603.5.7 Outlets with Hose Attachments. Potable water outlets with hose attachments, other than water heater drains, boiler drains, and clothes washer connections, shall be protected by a nonremovable hose bibbtype backflow preventer, a nonremovable hose bibb-type vacuum breaker, or by an atmospheric vacuum breaker installed not less than 6 inches (152 mm) above the highest point of usage located on the discharge side of the last valve. In climates where freezing temperatures occur, a listed self-draining frost-proof hose bibb with an integral backflow preventer or vacuum breaker shall be used. 603.5.8 Water-Cooled Equipment. Water-cooled compressors, degreasers, or other water-cooled equipment shall be protected by a backflow preventer installed in accordance with the requirements of this chapter. Water-cooled equipment that produces backpressure shall be equipped with the appropriate protection. 603.5.9 Aspirators. Water inlets to water-supplied aspirators shall be equipped with a vacuum breaker installed in accordance with its listing requirements and this chapter. The discharge shall drain through an air gap. Where the tailpiece of a fixture to receive the discharge of an aspirator is used, the air gap shall be located above the flood-level rim of the fixture.

603.5.10 Steam or Hot Water Boilers. Potable water connections to steam or hot water boilers shall be protected from backflow by a double check valve backflow prevention assembly, backflow preventer with intermediate atmospheric vent and pressure reducing valve, or reduced pressure principle backflow prevention assembly in accordance with Table 603.2. Where chemicals are introduced into the system a reduced pressure principle backflow prevention assembly shall be provided in accordance with Table 603.2.

603.5.11 Nonpotable Water Piping. In cases where it is impractical to correct individual cross-connections on the domestic waterline, the line supplying such outlets

shall be considered a nonpotable water line. No drinking or domestic water outlets shall be connected to the nonpotable waterline. Where possible, portions of the nonpotable waterline shall be exposed, and exposed portions shall be properly identified in a manner satisfactory to the Authority Having Jurisdiction. Each outlet on the nonpotable waterline that is permitted to be used for drinking or domestic purposes shall be posted: “CAUTION: NONPOTABLE WATER, DO NOT DRINK.”

[HCD 1 & HCD 2] An international symbol of a glass in a circle with a slash through it shall be provided sim- ilar to that shown in Figure 601.
CMC § 601.8.1.1 High relevance — show source text
601.8.1.1 Equipment using potable water shall be so installed as to prevent back-siphonage into the potable water system.

601.8.1.2 Non-potable water is permitted only in those parts of o ffi cial plants where no edible product is han- dled or prepared, and then only for limited purposes, such as on ammonia condensers not connected with the potable water supply, in vapor lines serving inedi- ble product rendering tanks, in connection with equip- ment used for washing and washing inedible products preparatory to tanking, and in sewer lines for moving heavy solids in sewage. In all cases, non-potable water lines shall be clearly identi fi ed and shall not be cross connected with the potable water supply.

Exception: Cross connection is permitted if this is necessary for fi re protection, and such connection is of a type with a break to ensure against accidental contamination, and is approved by local authorities or by the Department.

601.8.2 All pipelines, reservoirs, tanks, cooling towers, and like equipment employed in handling reused water shall be constructed and installed so as to facilitate their cleaning and inspection.

601.8.3 Hot water for cleaning rooms and equipment shall be delivered under pressure to outlets and shall be of such temperature as to accomplish a thorough cleanup.

601.8.3.1 An ample supply of water at not less than 180°F (82°C) shall be available when used for san- itizing purposes.

601.8.4 Pens, alleys, and runways shall have hose con- nections for cleanups purposes.

602.0 Unlawful Connections.

602.1 Prohibited Installation. No installation of potable water supply piping, or part thereof, shall be made in such a manner that it will be possible for used, unclean, polluted, or contaminated water, mixtures, or substances to enter a portion of such piping from a tank, receptor, equipment, or plumbing fixture by reason of backsiphonage, suction, or other cause, either during normal use and operation thereof, or where such tank, receptor, equipment, or plumbing fixture is flooded or subject to pressure exceeding the operating pressure in the hot or cold water piping. 602.2 Cross-Contamination. No person shall make a connection or allow one to exist between pipes or conduits carrying domestic water supplied by a public or private building supply system, and pipes, conduits, or fixtures containing or carrying water from any other source or containing or carrying water that has been used for any purpose whatsoever, or piping carrying chemicals, liquids, gases, or substances whatsoever, unless there is provided a backflow prevention device approved for the potential hazard and maintained in accordance with this code. Each point of use shall be separately protected where potential cross-contamination of individual units exists.

602.3 Backflow Prevention. No plumbing fixture, device, or construction shall be installed or maintained, or shall be connected to a domestic water supply, where such installation or connection provides a possibility of polluting such water supply or cross-connection between a distributing system of water for drinking and domestic purposes and water that becomes contaminated by such plumbing fixture, device, or construction unless there is provided a backflow prevention device approved for the potential hazard.
CMC § 603.3 High relevance — show source text
Testing or maintenance shall be performed by a certified backflow assembly tester or repairer certified in accordance with ASSE/IAPMO/ANSI Series 5000 or any other additional certification approved by the Authority Having Jurisdiction.

603.3 Backflow Prevention Devices, Assemblies, and Methods. Backflow prevention devices, assemblies, and methods shall comply with Section 603.3.1 through Section 603.3.12.

603.3.1 Air Gap. The minimum air gap to afford backflow protection shall be in accordance with Table 603.3.1. 603.3.2 Atmospheric Vacuum Breaker (AVB). An atmospheric vacuum breaker consists of a body, a checking member, and an atmospheric port.

603.3.3 Hose Connection Backflow Preventer. A hose connection backflow preventer consists of two independent check valves with an independent atmospheric vent between and a means of field testing and draining.

603.3.4 Double Check Valve Backflow Prevention Assembly (DC). A double check valve backflow prevention assembly consists of two independently acting internally loaded check valves, four properly located test cocks, and two isolation valves.

603.3.5 Pressure Vacuum Breaker Backflow Pre- vention Assembly (PVB). A pressure vacuum breaker backflow prevention assembly consists of a loaded air inlet valve, an internally loaded check valve, two properly located test cocks, and two isolation valves. This device shall be permitted to be installed indoors where provisions for spillage are provided. 603.3.6 Spill-Resistant Pressure Vacuum Breaker (SVB). A pressure-type vacuum breaker backflow prevention assembly consists of one check valve force loaded closed and an air inlet vent valve force loaded open to atmosphere, positioned downstream of the check valve and located between and including two tightly closing shutoff valves and test cocks. 603.3.7 Reduced-Pressure Principle Backflow Prevention Assembly (RP). A reduced-pressure principle backflow prevention assembly consists of two independently acting internally loaded check valves, a differential pressure relief valve, four properly located test cocks, and two isolation valves.

603.3.8 Double Check Detector Fire Protection Backflow Prevention Assembly. A double check valve backflow prevention assembly with a parallel

detector assembly consisting of a water meter and a double check valve backflow prevention assembly (DC).

603.3.9 Reduced Pressure Detector Fire Protec- tion Backflow Prevention Assembly. A reducedpressure principle backflow prevention assembly with a parallel detector assembly consisting of a water meter and a reduced-pressure principle backflow prevention assembly (RP).

603.3.10 Dual Check Backflow Preventer. A dual check backflow preventer consists of two independently acting check valves, force loaded to a normally closed position.

603.3.11 Laboratory Faucet Backflow Preven- ters. Laboratory faucet backflow preventers shall comply with ASSE 1035.

603.3.12 Backflow Preventer with Intermediate Atmospheric Vent. A backflow preventer with intermediate atmospheric vent consists of two independently acting check valves, force loaded to a normally closed position, and an intermediate chamber with a means for automatically venting to atmosphere, force loaded to a normally open position. 603.4 General Requirements. Assemblies shall comply with listed standards and be acceptable to the Authority Having Jurisdiction, with jurisdiction over the selection and installation of backflow prevention assemblies.

**603.4.1 Backflow Prevention Valve.
CMC § 5703.6.4 High relevance — show source text
Exception: Vapor-recovery piping is allowed to be tested using an inert gas.

5703.6.4 Protection from vehicles. Guard posts or other approved means shall be provided to protect piping, valves or fittings subject to vehicular damage in accordance with Section 312.

5703.6.5 Protection from external corrosion and galvanic action. Where subject to external corrosion, piping, related fluidhandling components and supports for both underground and above-ground applications shall be fabricated from noncorrosive materials, and coated or provided with corrosion protection. Dissimilar metallic parts that promote galvanic action shall not be joined.

5703.6.6 Valves. Piping systems shall contain a sufficient number of manual control valves and check valves to operate the system properly and to protect the plant under both normal and emergency conditions. Piping systems in connection with pumps shall contain a sufficient number of such valves to control properly the flow of liquids in normal operation and in the event of physical damage or fire exposure.

5703.6.6.1 Backflow protections. Connections to pipelines or piping by which equipment (such as tank cars, tank vehicles or marine vessels) discharges liquids into storage tanks shall be provided with check valves or block valves for automatic protection against backflow where the piping arrangement is such that backflow from the system is possible. Where loading and unloading is done through a common pipe system, a check valve is not required. However, a block valve, located in an area where it is provided with ready access or remotely operable, shall be provided.

5703.6.6.2 Manual drainage. Manual drainage-control valves shall be located at approved locations remote from the tanks, diked area, drainage system and impounding basin to ensure their operation in a fire condition.

5703.6.7 Connections. Above-ground tanks with connections located below normal liquid level shall be provided with internal or external isolation valves located as close as practical to the shell of the tank. Except for liquids whose chemical characteristics are incompatible with steel, such valves, where external, and their connections to the tank shall be of steel.

5703.6.8 Piping supports. Piping systems shall be substantially supported and protected against physical damage and excessive stresses arising from settlement, vibration, expansion, contraction or exposure to fire. The supports shall be protected against exposure to fire by one of the following:
1. Draining liquid away from the piping system at a minimum slope of not less than 1 percent.
2. Providing protection with a fire-resistance rating of not less than 2 hours.
3. Other approved methods.
5703.6.9 Flexible joints. Flexible joints shall be listed and approved and shall be installed on underground liquid, vapor and vent piping at all of the following locations:
1. Where piping connects to underground tanks.
2. Where piping ends at pump islands and vent risers.
3. At points where differential movement in the piping can occur.
5703.6.9.1 Fiberglass-reinforced plastic piping. Fiberglass-reinforced plastic (FRP) piping is not required to be provided with flexible joints in locations where both of the following conditions are present:
1. Piping does not exceed 4 inches (102 mm) in diameter.
2. Piping has a straight run of not less than 4 feet (1219 mm) on one side of the connection where such connections result in a change of direction.
In lieu of the minimum 4-foot (1219 mm) straight run length, approved and listed flexible joints are allowed to be used under dispensers and suction pumps, at submerged pumps and tanks, and where vents extend above ground.
CMC § 603.5.14.2 High relevance — show source text
(1) Reduced pressure principle backflow prevention assembly (RP)

(2) Reduced pressure detector fire protection backflow prevention assembly

Nonpotable water sources include fire department vehicles carrying water of questionable quality or water that is treated with antifreeze, corrosion inhibitors, or extinguishing agents. 603.5.14.2 Chemicals. Where antifreeze, corrosion inhibitors, or other chemicals are added to a fire protection system supplied from a potable water supply, the potable water system shall be protected by one of the following:

(1) Reduced pressure principle backflow prevention assembly (RP)

(2) Reduced pressure detector fire protection backflow prevention assembly 603.5.14.3 Hydraulic Design. Where a backflow device is installed in the potable water supply to a fire protection system, the hydraulic design of the system shall account for the pressure drop through the backflow device. Where such devices are retrofitted for an existing fire protection system, the hydraulics of the sprinkler system design shall be checked to verify that there will be sufficient water pressure available for satisfactory operation of the fire sprinklers. 603.5.15 Health Care or Laboratory Areas. Vacuum breakers for washer-hose bedpans shall be located not less than 5 feet (1524 mm) above the floor. Hose con

nections in health care or laboratory areas shall be not less than 6 feet (1829 mm) above the floor. 603.5.16 Special Equipment. Portable cleaning equipment and dental vacuum pumps shall be protected from backflow by an air gap, an atmospheric vacuum breaker, a spill-resistant vacuum breaker, or a reduced pressure principle backflow preventer.

603.5.17 Potable Water Outlets and Valves. Potable water outlets, freeze-proof yard hydrants, combination stop-and-waste valves, or other fixtures that incorporate a stop and waste feature that drains into the ground shall not be installed underground. 603.5.18 Pure Water Process Systems. The water supply to a pure water process system, such as dialysis water systems, semiconductor washing systems, and similar process piping systems, shall be protected from backpressure and backsiphonage by a reduced-pressure principle backflow preventer. 603.5.18.1 Dialysis Water Systems. The individual connections of the dialysis related equipment to the dialysis pure water system shall not require additional backflow protection. 603.5.19 Garbage Can Washers. Where garbage can washers are connected to a potable water supply system, the connection shall be protected against backflow in accordance with Table 603.2.

603.5.20 Plumbing Fixture Fittings. Plumbing fixture fittings with integral backflow protection shall comply with ASME A112.18.1/CSA B125.1. 603.5.21 Swimming Pools, Spas, and Hot Tubs. Potable water supply to swimming pools, spas, and hot tubs shall be protected by an air gap or a reduced pressure principle backflow preventer in accordance with the following:

(1) The unit is equipped with a submerged fill line.

(2) The potable water supply is directly connected to the unit circulation system. 603.5.22 Chemical Dispensers. The water supply to chemical dispensers shall be protected against backflow by one of the following:

CMC § 1501.7 High relevance — show source text

348 2025 CALIFORNIA PLUMBING CODE

REFERENCED STANDARDS

TABLE 1701.1 (continued) REFERENCED STANDARDS

STANDARD NUMBER	STANDARD TITLE	APPLICATION	REFERENCED SECTION
IAPMO/ANSI Z601-2018	Scale Reduction Devices	Water Conditioning, Water Treatment	611.1.2
ANSI/CAN/IAPMO Z1001- 2021	Prefabricated Gravity Grease Interceptors	Fixtures	Table 1009.1, 1014.1,

CMC § 1503.1.1 High relevance — show source text
(1) [HCD 1] The prohibition in Subsection (F) includes, but is not limited to, home photo labs or other similar hobbyist or home occupational activities.

(2) [BSC-CG] Photo labs or similar activities.

(G) Exemption from construction permit requirements of this code shall not be deemed to grant authorization for any

gray water system to be installed in a manner that vio- lates other provisions of this code or any other laws or ordinances of the Enforcing Agency.

(H) An operation and maintenance manual shall be provided to the owner. Directions shall indicate that the manual is to remain with the building throughout the life of the system and upon change of ownership or occupancy.

(I) A gray water system shall not be connected to any potable water system without an air gap, reduced-pressure prin- ciple backflow preventer, or other physical device which prevents backflow and shall not cause ponding or runoff of gray water.

1503.1.1 Clothes Washer System. [HCD 1] A clothes washer system in compliance with all of the fol- lowing is exempt from the construction permit specified in Section 1.8.4.1 and may be installed or altered with- out a construction permit:

(1) If required, notification has been provided to the enforcing agency regarding the proposed location and installation of a gray water irrigation or dis- posal system.

(2) The design shall allow the user to direct the flow to the irrigation or disposal field or the building sewer. The direction control of the gray water shall be clearly labeled and readily accessible to the user.

(3) The installation, change, alteration, or repair of the system does not include a potable water connection or a pump and does not affect other building, plumb- ing, electrical, or mechanical components including structural features, egress, fire-life safety, sanitation, potable water supply piping, or accessibility.

Note: The pump in a clothes washer shall not be considered part of the gray water system.

(4) The gray water shall be contained on the site where it is generated.

(5) Gray water shall be directed to and contained within an irrigation or disposal field.

(6) Ponding or runoff is prohibited and shall be consid- ered a nuisance.

(7) Gray water may be released above the ground sur- face provided at least two (2) inches (51 mm) of mulch, rock, or soil, or a solid shield covers the release point. Other methods which provide equiva- lent separation are also acceptable.

(8) Gray water systems shall be designed to minimize contact with humans and domestic pets.

(9) Water used to wash diapers or similarly soiled or infectious garments shall not be used and shall be diverted to the building sewer.

(10)Gray water shall not contain hazardous chemicals derived from activities such as cleaning car parts, washing greasy or oily rags, or disposing of waste solutions from home photo labs or similar hobbyist or home occupational activities.

312 2025 CALIFORNIA PLUMBING CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

ALTERNATE WATER SOURCES FOR NONPOTABLE APPLICATIONS
CMC § 1501.0 Medium 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
CMC § 1502.4 Medium relevance — show source text
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

1504.2 Required Area of Subsurface Irrigation Fields, Subsoil Irrigation Fields, and Mulch Basins . . . . . . . . . . . . . . . .316

1504.3 Determination of Maximum

Absorption Capacity . . . . . . . . . . .316

Table 1504.2 Design of Six Typical Soils . . . . . .316

1504.4 Groundwater Level . . . . . . . . . . . .316

1504.5 Irrigation, Disposal Field and Mulch Basin Construction . . . . . .316

Table 1504.5.3 Subsoil Irrigation Field Construction . . . . . . . . . . . . . . . . .318

Table 1504.5.5 Subsurface Irrigation Design Criteria for Six Typical Soils . . . . .318

1504.6 Reserved . . . . . . . . . . . . . . . . . . .318

1504.7 Reserved . . . . . . . . . . . . . . . . . . .318

1504.8 Gray Water System Color and Marking Information . . . . . . . .318

1504.9 Other Collection and

Distribution Systems . . . . . . . . . . .318

1504.10 Testing . . . . . . . . . . . . . . . . . . . . .318

1504.11 Maintenance . . . . . . . . . . . . . . . . .318

1505.0 Recycled Water Supply Systems in Buildings . . . . . . . . . .318
California Mechanical Code Medium relevance — show source text
RATING IN THOUSANDS OF BTU PER HOUR**|APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR| |HEIGHT
H
(feet)|LATERAL
L
(feet)|MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR| |6|0
2
5|39
31
28|70
55
51|116
94
88|170
141
128|232
194
177|312
260
242|500
415
390|750
620
600| |8|0
2
5
10|42
32
29
24|76
61
56
49|126
102
95
86|185
154
141
131|252
210
194
180|340
284
264
250|542
451
430
406|815
680
648
625| |10|0
2
5
10
15|45
35
32
27
NA|84
67
61
54
46|138
111
104
94
84|202
168
153
143
130|279
233
215
200
186|372
311
289
274
258|606
505
480
455
432|912
760
724
700
666| |15|0
2
5
10
15
20|49
39
35
30
NA
NA|91
72
67
58
50
NA|151
122
110
103
93
82|223
186
170
158
144
132|312
260
240
223
207
195|420
350
325
308
291
273|684
570
540
514
488
466|1040
865
825
795
760
726| |20|0
2
5
California Mechanical Code Medium relevance — show source text

2
5
10
15
20
30|184
175
215
265
312
360
461|1168
823
806
777
750
723
670|647
533
521
501
481
461
426|229
219
269
327
379
433
541|1542
1069
1049
1017
985
955
895|852
698
684
662
638
615
574|312
296
366
440
507
570
704|1971
1346
1324
1287
1251
1216
1147|1056
863
846
821
794
768
720|454
424
524
620
702
780
937|2996
1999
1971
1927
1884
1841
1759|1545
1308
1283
1243
1205
1166
1101| |50|0
2
5
10
15
20
30|176
168
204
253
299
345
442|1292
971
953
923
894
866
809|704
613
602
583
562
543
502|220
209
257
313
363
415
521|1724
1273
1252
1217
1183
1150
1086|948
811
795
765
736
708
649|295
280
347
418
481
544
674|2223
1615
1591
1551
1512
1473
1399|1189
1007
991
963
934
906
848|428
401
496
589
668
741
892|3432
2426
2396
2347
2299
2251
2159|1818
1509
1490
1455
1421
1387
1318| |100|0
2
5
CMC § 1220.4.2 Medium relevance — show source text
8|1220.4.2 – 1220.4.6| |1221.7|1221.6| |1308.2 – 1308.4.1|1308.3 – 1308.5.1| |Table 1308.3.1|Table 1308.4.1| |1308.4.2|1308.5.2| |1308.4.2.2 – 1308.6.4|1308.5.2.1 – 1308.7.3| |Table 1308.4.6.2|Table 1308.5.6.2| |1308.6.5 – 1308.13.1|1308.7.7 – 1308.14.1| |1312.1.2 – 1312.1.3|1312.1.1 – 1312.1.2| |Chapter 17|Appendix F| |Chapter 18|Chapter 17| |D 103.2|D 103.1| |E 503.5.6.7|E 503.5.6.6| |E 503.5.7.2 – E 503.5.7.6|E 503.5.7.1 – E 503.5.7.5| |Table E 503.5.7.2|Table E 503.5.7.1| |Table E 503.5.7.6|Table E 503.5.7.5| |Table E 503.5.10.1.2(1)|Table E 503.5.10(1)| |Table E 503.5.10.1.2(2)|Table E 503.5.10(2)| |E 503.5.10.1.2|E 503.5.10| |E 503.5.10.2 – E 503.5.10.2.2|E 503.5.10.1 – E 503.5.10.1.2| |E 503.5.12.1|E 503.5.12| |E 503.5.12.2|E 503.5.12.1| |E 503.6.5.4|E 503.6.5.4.1|

xxii 2025 CALIFORNIA MECHANICAL CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

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Uniform Mechanical Code – 2024 Edition:

The Uniform Mechanical Code contains complete requirements for the installation and maintenance of heating, ventilating, cooking and refrigeration systems.

Uniform Mechanical Code Illustrated Training Manual:
CMC § 2024 Medium relevance — show source text
Important Notices and Disclaimers The 2024 edition of the Uniform Mechanical Code is developed through a consensus standards development process approved by the American National Standards Institute. This process brings together volunteers representing varied viewpoints and interests to achieve consensus on mechanical issues. While the International Association of Plumbing and Mechanical Officials (IAPMO) administers the process and establishes rules to promote fairness in the development of consensus, it does not independently test, evaluate, or verify the accuracy of any information or the soundness of any judgments contained in its codes

and standards.

IAPMO disclaims liability for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, or reliance on this document. IAPMO also makes no guarantee or warranty as to the accuracy or completeness of any information published

herein.

In issuing and making this document available, IAPMO is not undertaking to render professional or other services for or on behalf of any person or entity. Nor is IAPMO undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances.

Updating IAPMO Codes Users of IAPMO codes should be aware that IAPMO codes may be amended from time to time through the issuance of Tentative Interim Amendments or corrected by Errata. IAPMO codes consist of the current edition of the document together with any Tentative Interim Amendments and any Errata in effect.

To access information for a specific code or to determine whether an IAPMO code has been amended through the issuance of Tentative Interim Amendments or corrected by Errata, please visit the IAPMO codes information page on the IAPMO’s website (https://www.iapmo.org/code-development). The codes information page provides a list of IAPMO codes with up-to-date specific information including any issued Tentative Interim

Amendments and Errata.

x 2025 CALIFORNIA MECHANICAL CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

FOREWORD

Origin and Development The industry has long recognized the advantages of a statewide adopted mechanical code. The first edition of the Uniform Mechanical Code [®] (UMC [®] ) was adopted by IAPMO in 1967. The widespread use of this code over the past five decades by jurisdictions throughout the United States and internationally is testament to its merit.

Publishing of the 2003 Uniform Mechanical Code was a significant milestone because it was the first time in the history of the United States a mechanical code was developed through a true consensus process. The 2024 edition represents the most current approaches in the mechanical field and is the eighth edition developed under the ANSI consensus process. Contributions to the content of this code consists of diverse interests as consumers, enforcing authorities, installers/maintainers, labor, manufacturers, research/standards/testing laboratories, special experts, and users.

CMC § 304.8 Medium relevance — show source text

226
206|342
295
263
240|573
498
447
409|664
579
520
477|1130
974
870
793|1320
1140
1020
936|2340
2030
1820
1660|2630
2280
2040
1860|

For SI units: 1 foot = 304.8 mm, 1 cubic foot per hour = 0.0283 m [3] /h, 1 pound-force per square inch = 6.8947 kPa, 1 inch water column = 0.249 kPa

Notes: 1 Table entries are rounded to 3 significant digits. 2 Table includes losses for four 90 degree (1.57 rad) bends and two end fittings. Tubing runs with larger numbers of bends, fittings, or both shall be increased by an equiv alent length of tubing to the following equation: L = 1.3 n, where L is additional length (ft) of tubing and n is the number of additional fittings, bends, or both . 3 EHD = Equivalent Hydraulic Diameter, which is a measure of the relative hydraulic efficiency between different tubing sizes. The greater the value of EHD, the

greater the gas capacity of the tubing.

312 2025 CALIFORNIA MECHANICAL CODE

FUEL GAS PIPING

Col2	Col3	Col4	Col5	2, 3, 4	Col11	Col12	Col13	Col14	Col15
				GAS:	GAS:	GAS:	NATURAL	NATURAL	NATURAL
				INLET PRESSURE:	INLET PRESSURE:	INLET PRESSURE:	2.0 psi	2.0 psi	2.0 psi
				PRESSURE DROP:	PRESSURE DROP:	PRESSURE DROP:	1.0 psi	1.0 psi	1.0 psi
				SPECIFIC GRAVITY:	SPECIFIC GRAVITY:	SPECIFIC GRAVITY:	0.60	0.60	0.60
TUBE SIZE (EHD)5	TUBE SIZE (EHD)5	TUBE SIZE (EHD)5	**TUBE SIZE

California Mechanical Code Medium relevance — show source text

5
10
15
20|NA
NA
NA
NA
NA|NA
NA
NA
NA
NA|38
35
NA
NA
NA|NA
NA
NA
NA
NA|NA
NA
NA
NA
NA|73
67
59
NA
NA|NA
NA
NA
NA
NA|NA
NA
NA
NA
NA|123
115
105
95
80|NA
NA
NA
NA
NA|NA
NA
NA
NA
NA|200
183
170
156
144|163
NA
NA
NA
NA|520
NA
NA
NA
NA|273
252
235
217
202| |30|2
5
10
15
20
30|NA
NA
NA
NA
NA
NA|NA
NA
NA
NA
NA
NA|41
NA
NA
NA
NA
NA|NA
NA
NA
NA
NA
NA|NA
NA
NA
NA
NA
NA|81
75
66
NA
NA
NA|NA
NA
NA
NA
NA
NA|NA
NA
NA
NA
NA
NA|136
127
113
105
88
NA|NA
NA
NA
NA
NA
NA|NA
NA
NA
NA
NA
NA|215
196
182
168
155
NA|158
NA
NA
NA
NA
NA|578
NA
NA
NA
NA
NA|302
279
260
240
223
182| |50|2
5
10
15
20
30|NA
NA
NA
NA
NA
NA|NA
NA
NA
NA
NA
NA|NA
NA
NA
NA
NA
NA|NA
NA
NA
NA
NA
NA|NA
NA
NA
NA
NA
NA|91
NA
NA
NA
NA
NA|NA
NA
NA
NA
NA
NA|NA
NA
NA
NA
NA
NA|160
149
136
124
NA
NA|NA
NA
NA
NA
NA
NA|NA
NA
NA
NA
NA
NA|250
228
212
195
180
NA|NA
NA
NA
NA
NA
NA|NA
NA
NA
NA
NA
NA|350
321
301
278
258
NA| |Minimum
internal area of
chimney
(square inches)|Minimum
internal
CMC § 304.8 Medium relevance — show source text
r>37
35
34|83
79
76
73
70|169
161
155
148
143|296
282
270
260
250|420
400
383
368
355|896
855
819
787
758|1610
1540
1470
1420
1360|2540
2430
2320
2230
2150|5300
5050
4840
4650
4480| |1600
1700
1800
1900
2000|1600
1700
1800
1900
2000|33
32
31
30
29|68
66
64
62
60|138
134
130
126
122|241
234
227
220
214|343
331
321
312
304|732
708
687
667
648|1320
1270
1240
1200
1170|2080
2010
1950
1890
1840|4330
4190
4060
3940
3830|

For SI units: 1 inch = 25 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 pound-force per square inch = 6.8947 kPa

Notes: 1 Table capacities are based on Type K copper tubing inside diameter (shown), which has the smallest inside diameter of the copper tubing products. 2 Table entries are rounded to 3 significant digits.

2025 CALIFORNIA MECHANICAL CODE 323

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Frequently asked questions

Do I follow the Mechanical Code or Plumbing Code for backflow on mechanical equipment?

You must follow the California Plumbing Code (CPC) cross‑connection rules for potable water connections and backflow prevention; the Mechanical Code may reference or rely on plumbing requirements but the CPC contains the specific backflow device selections and testing rules (see § 603.0 and related subsections) .

Is an air gap ever acceptable for mechanical equipment?

Yes — an approved air gap can be acceptable for many inlets (tanks, sumps, pools) where an open discharge prevents backflow. Air gaps must meet the minimum dimensions in the CPC (Table 603.3.1) or be part of a listed assembly .

When is a reduced‑pressure (RP) assembly mandatory?

When the system can create backpressure (pumps, booster pumps) or when chemicals or other high‑hazard contaminants can enter the water (chemical injectors, antifreeze), the CPC requires an RP (see § 603.5.6.1 and § 603.5.6.3) .

Who tests and maintains backflow assemblies?

Testing and maintenance must be performed by a certified backflow assembly tester/repairer; the CPC mandates testing at installation and at least annually (or more often if the AHJ requires) .

I need the exact text of CMC § 312.1 / § 312.0 — can you provide it?

I cannot provide or quote those CMC paragraphs because the uploaded CMC files did not include the specific text of § 312.0 or § 312.1; the available Mechanical Code copy shows the 312 chapter heading (fuel gas piping) but not the specific sections requested .

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Related in the CMC

How must HVAC condensate drains be sized and routed?

Where can condensate discharge and when are drainage pans required?

Condensate, drainage, and plumbing connections

California Mechanical Code