CPC · California Plumbing Code

What clearances and accessibility are required for water heaters?

Q: What if the manufacturer’s instructions say less clearance than 12 inches?

For listed appliances, follow the listing/manufacturer’s instructions; listed clearances control for listed units as described in § 504.3.1 . For unlisted units, the code requires 12 in on all sides per § 504.3.2 .

Q: Can the T&P valve discharge go into the pan?

No. Discharge from a relief valve into a drainage pan is prohibited by § 507.5 (4) and discharge piping rules in § 608.5 .

Q: How big must the pan drain be and where must it terminate?

The pan drain must be at least 3/4 in (20 mm) diameter and terminate to an approved location with the terminating end readily visible , per § 507.5 (1) .

Q: Is 30 inches of clearance always required in front of the heater?

The code’s default service/work space is 30 in (depth, width, height) per § 507.25 , unless another section or the appliance listing specifies otherwise.

Homeowners: Listed water heaters must be installed per the manufacturer so they don’t block combustion air or service access; unlisted units need at least 12 inches of clearance on every side. If the heater is in an attic or could leak into the structure, the CPC requires a corrosion‑resistant pan (≥1½ in deep) with a visible drain of at least 3/4 in, and the relief valve must not discharge into that pan.

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Last reviewed: July 6, 2026

What the code requires — plain English

Water heaters must be installed so they do not block required combustion air, the draft hood or vent relief, or access needed for servicing. For listed water heaters follow the appliance listing and the manufacturer’s instructions; unlisted water heaters must have at least 12 inches (305 mm) clearance on all sides and combustible floors under them must be protected. These rules are established in § 504.3 and its subsections.

The single most important rule: Listed units must be installed per their listing/manufacturer so they do not interfere with combustion air, draft hood relief, or servicing; unlisted units require a minimum 12 in clearance on all sides. § 504.3.

Requirements in detail

Which clearance rule applies

Listed water heaters — follow the clearances in the listing and the manufacturer’s installation instructions; clearances must not interfere with combustion air, draft hood relief, or accessibility for servicing. § 504.3.1.
Unlisted water heaters — minimum 12 inches (305 mm) on all sides; combustible floors under unlisted units must be protected. § 504.3.2.

Working/Service space

Installations must allow access for repair or replacement and maintenance tasks. Unless otherwise specified, maintain not less than 30 inches (762 mm) of working space (depth, width, and height) to permit servicing and removal of the appliance. § 507.25.

Drainage pan requirements (attics and locations where leaks can cause damage)

When a water heater is in an attic (or in/on assemblies where leaking causes damage) a watertight pan is required with the following minimum features per § 507.5:

Pan must be made of corrosion‑resistant material.
Pan drain: not less than 3/4 inch (20 mm) diameter to an approved, readily visible termination.
Pan depth: not less than 1 1/2 inches (38 mm).
Drain piping must be rated for the water temperature and approved for the discharge medium.
Discharge from a relief valve into a drainage pan is prohibited. (Also see discharge piping rules in § 608.5.)

Short decision table (quick reference)

Issue / dimension	Required value or rule	Code reference
Clearance for unlisted water heaters	12 in (305 mm) on all sides; protect combustible floor under unit	§ 504.3.2
Clearance for listed water heaters	Follow listing and manufacturer’s instructions; must not interfere with combustion air, draft hood relief, or servicing	§ 504.3.1 § 504.3
Minimum working/service space (unless otherwise specified)	30 in (762 mm) depth, width, and height	§ 507.25
Water‑heater drainage pan required (attic / where leaks cause damage)	Watertight, corrosion‑resistant pan; pan depth ≥ 1½ in (38 mm)	§ 507.5 (2)
Pan drain	≥ 3/4 in (20 mm) diameter to approved location; terminating end readily visible	§ 507.5 (1)
Pan drain piping	Rated for water temp and approved for liquid discharged	§ 507.5 (3)
Relief valve discharge into pan	Prohibited	§ 507.5 (4) § 608.5

Exceptions & special cases

Manufacturer listings: If the appliance listing or manufacturer instructions specify different clearances, those listed clearances control for listed appliances (see § 504.3.1).
Attic / roof / confined spaces: Additional access and passageway rules (for attic installations, see the appliance-access rules and Section 508.4) may apply — confirm access route and working space per the referenced sections.
Unlisted appliances must be approved by the Authority Having Jurisdiction before installation and must meet the 12 in clearance and combustible-floor protection requirements in § 504.3.2.

Common mistakes

Assuming “no clearance” because a unit is compact — always check the appliance listing and manufacturer instructions for listed units; otherwise apply § 504.3.2 for unlisted units.
Routing a temperature/pressure relief (T&P) valve discharge into a water‑heater pan — this is explicitly prohibited. § 507.5 (4) and § 608.5.
Providing too little working space in front of the unit — the default 30 in working space is commonly overlooked. § 507.25.
Forgetting to make the pan‑drain terminating point readily visible, or using drain piping not rated for hot water — both are required by § 507.5.

Worked example — attic gas storage water heater replacement

Scenario: Replace an existing 40‑gal gas storage water heater located in an attic where a leak would damage the ceiling below.

Steps to comply (numbers pulled from the CPC):

Determine whether the replacement unit is listed. If the new heater is listed, obtain and follow the manufacturer’s required clearances so as not to interfere with combustion air, draft hood relief, or servicing (§ 504.3.1).
If the replacement were unlisted, provide 12 in (305 mm) clearance on all sides and protect combustible floor beneath the unit (§ 504.3.2).
Provide at least 30 in (762 mm) of working space where required for servicing and removal, unless the manufacturer/listing requires more (§ 507.25).
Install a watertight, corrosion‑resistant pan under the heater because it is in the attic. Select a pan with depth ≥ 1½ in (38 mm) and fit a drain of at least 3/4 in (20 mm) diameter. Route the drain to an approved, readily visible termination (for example, into an accessible roof drain receptor or a visible overflow to the exterior) using piping rated for hot water per § 507.5 (1)–(3).
Ensure the T&P valve discharge is piped per § 608.5 — do not route the T&P discharge into the drainage pan (this is prohibited by § 507.5 (4) and reinforced by § 608.5).

Practical numbers recap for this attic example: pan depth ≥ 1.5 in, pan drain ≥ 3/4 in, service clearance ≥ 30 in in front (unless manufacturer specifies differently), and side clearances per listing or 12 in if unlisted.

Related provisions (quick pointers)

§ 504.3 — General clearance direction; see subsections § 504.3.1 and § 504.3.2.
§ 504.3.1 — Listed water heaters: follow listing and manufacturer instructions.
§ 504.3.2 — Unlisted water heaters: 12 in clearance and combustible-floor protection.
§ 507.5 — Drainage pan requirements (attic/locations where leaks cause damage).
§ 507.25 — Accessibility for service; default 30 in working space.
§ 507.26 — Clearance to combustible materials (see for specifics on combustible clearances).
§ 506.0 — Combustion air requirements (ensure clearances do not interfere with required combustion air).
§ 608.5 — Discharge piping rules for relief valves (no discharge into pan; piping size, routing, termination visibility).

Code references

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

CPC § 3.785 High relevance — show source text
For SI units: 1 gallon = 3.785 L

Notes: 1 The first-hour rating is found on the “Energy Guide” label. 2 Solar water heaters shall be sized to meet the appropriate first-hour rating as shown in the table.

2025 CALIFORNIA PLUMBING CODE 83

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WATER HEATERS

Exception: Where acceptable to the Authority Having Jurisdiction, gasketing of non-combustible or limitedcombustible material shall be permitted to be applied to the frame, provided closing and latching of the door are not inhibited.

504.2 Vent. Water heaters of other than the direct-vent type shall be located as close as practical to the chimney or gas vent. 504.3 Clearance. The clearance requirements for water heaters shall comply with Section 504.3.1 or Section 504.3.2.

504.3.1 Listed Water Heaters. The clearances shall not be such as to interfere with combustion air, draft hood clearance and relief, and accessibility for servicing. Listed water heaters shall be installed in accordance with their listings and the manufacturer’s installation instructions. 504.3.2 Unlisted Water Heaters. Except as otherwise permitted in this code, unlisted water heaters shall be approved by the Authority Having Jurisdiction prior to being installed. Clearance for unlisted water heaters shall be not less than 12 inches (305 mm) on all sides. Combustible floors under unlisted water heaters shall be protected in an approved manner. {NFPA 54-2018:10.27.2.2} 504.4 Pressure-Limiting Devices. A water heater installation shall be provided with overpressure protection using an approved, listed device installed in accordance with the terms of its listing and the manufacturer’s installation instructions. Pressure relief devices shall have a pressure setting greater than the water service pressure and not exceed 150 psi (1034 kPa) as required in Section 608.4. 504.5 Temperature Limiting Devices. A water heater installation or a hot water storage vessel installation shall be provided with overtemperature protection by means of an approved, listed device installed in accordance with the terms of its listing and the manufacturer’s installation instructions. {NFPA 54:10.26.5} 504.6 Temperature, Pressure, and Vacuum Relief Devices. Temperature, pressure, and vacuum relief devices or combinations thereof, and automatic gas shutoff devices shall be installed in accordance with the terms of their listings and the manufacturer’s installation instructions. A shutoff valve shall not be placed between the relief valve and the water heater or on discharge pipes between such valves and the atmosphere. The hourly British thermal units (Btu) (kW•h) discharge capacity or the rated steam relief capacity of the device shall be not less than the input rating of the water heater. {NFPA 54:10.26.6} Discharge piping shall be installed in accordance with Section 608.5.

504.7 Lead Content. Water heaters shall comply with the lead content requirements of Section 604.2.
CPC § 9.1.20 High relevance — show source text
** The installer shall conform to the appliance and equipment manufacturers’ recommendations in completing an installation. The installer shall leave the manufacturers’ installation, operating, and maintenance instructions on the premises. [NFPA 54:9.1.20] 507.24 Protection of Outdoor Appliances. Appliances not listed for outdoor installation but installed outdoors shall be provided with protection to the degree that the environment requires. Appliances listed for outdoor installation shall be permitted to be installed without protection in accordance with the manufacturer’s installation instructions. [NFPA 54:9.1.21] 507.25 Accessibility for Service. All appliances shall be located with respect to building construction and other equipment so as to permit access for repair or replacement of the appliance. Clearance shall be maintained to permit removal of the appliance; cleaning of heating surfaces; the replacement of filters, blowers, motors, burners, controls, and vent connections; the lubrication of moving parts where necessary; the adjustment and cleaning of burners and pilots; and the proper functioning of explosion vents, if provided. For attic installation, the passageway and servicing area adjacent to the appliance shall be in accordance with Section 508.4. {NFPA 54:9.2.1}

Unless otherwise specified, clearances of not less than 30 inches (762 mm) in depth, width, and height of working space shall be maintained. 507.26 Clearance to Combustible Materials. Appliances and their vent connectors shall be installed with clearances from combustible material so their operation does not create a hazard to persons or property. Minimum clearances between combustible walls and the back and sides of various conventional types of appliances and their vent connectors are specified in Section 509.0. [NFPA 54:9.2.2]

508.0 Appliances on Roofs, in Attics or Under-Floor Spaces. 508.1 General. Appliances on roofs shall be designed or enclosed so as to withstand climatic conditions in the area in which they are installed. Where enclosures are provided, each enclosure shall permit easy entry and movement, shall be of reasonable height, and shall have at least a 30 inch (762 mm) clearance between the entire service access panel(s) of the appliance, and the wall of the enclosure. [NFPA 54:9.4.1.1] 508.1.1 Load Capacity. Roofs on which appliances are to be installed shall be capable of supporting the additional load or shall be reinforced to support the additional load. [NFPA 54:9.4.1.2]

508.1.2 Fasteners. All access locks, screws, and bolts shall be of corrosion-resistant material. [NFPA 54:9.4.1.3]

90 2025 CALIFORNIA PLUMBING CODE

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WATER HEATERS

are utilized in lieu of guards or rails, they shall be a minimum of 42 inches (1067 mm) in height. [NFPA 54:9.4.3.3] 508.3.3 Permanent Lighting. Permanent lighting shall be provided at the roof access. The switch for such lighting shall be located inside the building near the access means leading to the roof. [NFPA 54:9.4.3.4] **508.4 Appliances in Attics and Under-Floor Spaces.

CPC § 504.0 High relevance — show source text

No appliance or part thereof shall be covered or concealed until the same has been inspected and approved by the Authority Having Jurisdiction.

504.0 Water Heater Requirements.

504.1 Location. Water heater installations in bedrooms and

bathrooms shall comply with one of the following [NFPA 54:10.27.1]:

(1) Water heater shall be of the direct-vent type. [NFPA 54:10.27.1(2)]

(2) Fuel-burning water heaters shall be permitted to be installed in a closet located in the bedroom or bathroom provided the closet is equipped with a listed, gasketed door assembly and a listed self-closing device. The selfclosing door assembly shall meet the requirements of Section 504.1.1. The door assembly shall be installed with a threshold and bottom door seal and shall meet the requirements of Section 504.1.2. Combustion air for such installations shall be obtained from the outdoors in accor dance with Section 506.4. The closet shall be for the

exclusive use of the water heater.

504.1.1 Self-Closing Doors. Self-closing doors shall swing easily and freely, and shall be equipped with a self-closing device to cause the door to close and latch each time it is opened. The closing mechanism shall not have a hold-open feature.

504.1.2 Gasketing. Gasketing on gasketed doors or frames shall be furnished in accordance with the published listings of the door, frame, or gasketing material manufacturer.

TABLE 501.1(2) FIRST HOUR RATING [1]

Number of Bathrooms	1 to 1.5	Col3	Col4	2 to 2.5	Col6	Col7	Col8	3 to 3.5	Col10	Col11	Col12
Number of Bedrooms	1	2	3	2	3	4	5	3	4	5	6
First Hour Rating,2 Gallons	38	49	49	49	62	62	74	62	74	74	74

For SI units: 1 gallon = 3.785 L

Notes: 1 The first-hour rating is found on the “Energy Guide” label. 2 Solar water heaters shall be sized to meet the appropriate first-hour rating as shown in the table.

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WATER HEATERS

Exception: Where acceptable to the Authority Having Jurisdiction, gasketing of non-combustible or limitedcombustible material shall be permitted to be applied to the frame, provided closing and latching of the door are not inhibited.

504.2 Vent. Water heaters of other than the direct-vent type shall be located as close as practical to the chimney or gas vent. 504.3 Clearance. The clearance requirements for water heaters shall comply with Section 504.3.1 or Section 504.3.2.

504.3.1 Listed Water Heaters. The clearances shall not be such as to interfere with combustion air, draft hood clearance and relief, and accessibility for servicing.

CPC § 0.024 High relevance — show source text
024 inch (nominal 24 gauge)
sheet metal with ventilated air
space|18|12|9|6|6|4|5|3|3|2| |(6)
1⁄2 of an inch thick insulation
board with ventilated air space|18|12|9|6|6|4|5|3|3|3| |(7)
0.024 inch (nominal 24 gauge)
sheet metal with ventilated air
space over 0.024 inch (nomi-
nal 24 gauge) sheet metal with
ventilated air space|18|12|9|6|6|4|5|3|3|3| |(8)
1 inch glass fiber or mineral
wool batts sandwiched
between two sheets 0.024 inch
(nominal 24 gauge) sheet
metal with ventilated air space|18|12|9|6|6|4|5|3|3|3|

For SI units: 1 inch = 25.4 mm

Notes: 1 Reduction of clearances from combustible materials shall not interfere with combustion air, draft hood clearance and relief, and accessibility of servicing. 2 All clearances shall be measured from the outer surface of the combustible material to the nearest point on the surface of the appliance, disregarding any intervening protection applied to the combustible material. 3 Spacers and ties shall be of noncombustible material. No spacer or tie shall be used directly opposite the appliance or connector. 4 Where all clearance reduction systems use a ventilated air space, adequate provision for air circulation shall be provided as described. [See Figure 509.7.3.4(2) and Figure 509.7.3.4(3)] 5 At least 1 inch (25.4 mm) shall be between clearance reduction systems and combustible walls and ceilings for reduction systems using a ventilated air space. 6 Where a wall protector is installed on a single flat wall away from corners, it shall have a minimum 1 inch (25.4 mm) air gap. To provide adequate air circulation, the bottom and top edges, or only the side and top edges, or all edges shall be left open. 7 Mineral wool batts (blanket or board) shall have a minimum density of 8 pounds per cubic foot (lb/ft 3 ) (128 kg/m 3 ) and a minimum melting point of 1500°F (816°C). 8 Insulation material used as part of a clearance reduction system shall have a thermal conductivity of 1.0 British thermal unit inch per hour square foot degree Fahrenheit [Btu•in/(h•ft [2] - °F)] [0.1 W/(m•K)] or less. 9 At least 1 inch (25.4 mm) shall be between the appliance and the protector. The clearance between the appliance and the combustible surface shall not be

reduced below that allowed in this table. 10 All clearances and thicknesses are minimum; larger clearances and thicknesses are acceptable. 11 Listed single-wall connectors shall be installed in accordance with the terms of their listing and the manufacturer’s installation instructions.

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WATER HEATERS

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CPC § 17958.5. High relevance — show source text
Note: [HCD 1 & HCD 2] Reference Health and Safety Code Section 19211(a) which addresses new, replacement, and existing water heaters. Note: The applicable subsection of Health and Safety Code Sec- tion 19211(a) which addresses new, replacement, and existing water heaters is repeated here for clarity and reads as follows: Section 19211(a) Notwithstanding Section 19100, all new and replacement water heaters, and all existing residential water heaters shall be braced, anchored, or strapped to resist falling or horizontal displacement due to earthquake motion. At a minimum, any water heater shall be secured in accor- dance with the California Plumbing Code, or modifications made thereto by a city, county, or city and county pursuant to Section 17958.5.

507.3 Appliance Support. Appliances and equipment shall be furnished either with load distributing bases or with a suf

ficient number of supports to prevent damage to either the building structure or the appliance and the equipment. [NFPA 54:9.1.8.1] 507.3.1 Structural Capacity. At the locations selected for installation of appliances and equipment, the dynamic and static load carrying capacities of the building structure shall be checked to determine whether they are adequate to carry the additional loads. The appliances and equipment shall be supported and shall be connected to the piping so as not to exert undue stress on the connections. [NFPA 54:9.1.8.2] 507.4 Ground Support. A water heater supported from the earth shall rest on level concrete or other approved base extending not less than 3 inches (76 mm) above the adjoining ground level. 507.5 Drainage Pan. Where a water heater is located in an attic, in or on an attic ceiling assembly, floor-ceiling assembly, floor-subfloor assembly or where damage results from a leaking water heater, a watertight pan of corrosion-resistant materials shall be installed beneath the water heater in accordance with the following: (1) The drainage pan shall be provided with not less than [3] ⁄ 4 of an inch (20 mm) diameter drain to an approved location. The terminating end of the drainpipe shall be readily visible. (2) The drainage pan shall be not less than 1 [1] ⁄ 2 inches (38 mm) in depth. (3) Where a drainage pan pipe is installed, the material of the piping shall be rated for the temperature rating of the water heater and shall be approved for use with the liquid being discharged. (4) Discharge from a relief valve into a drainage pan shall be prohibited. 507.6 Added or Converted Equipment or Appliances. When additional or replacement appliances or equipment is installed or an appliance is converted to gas from another fuel, the location in which the appliances or equipment is to be operated shall be checked to verify the following: (1) Air for combustion and ventilation is provided where required, in accordance with the provisions of Section 506.0. Where existing facilities are not adequate, they shall be upgraded to meet Section 506.0 specifications. (2) The installation components and appliances meet the clearances to combustible material provisions of Section 507.26. It shall be determined that the installation and operation of the additional or replacement appliances do not render the remaining appliances unsafe for continued operation. (3) The venting system is constructed and sized in accordance with the provisions of Section 509.0.
CPC § 501.3.1 High relevance — show source text
E 501.3.1, E 501.6

Prohibited . . . . . . . . . . . . . . . . . . . . . . . . . .405.1, 910.7

Seats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .411.3

Water consumption . . . . . . . . . . . . . . . . .411.2, L 402.2

WATER-CONSERVING

FIXTURES AND FITTINGS . . . . . . . . . . . . . 401.3, L 402.0

WATER CONSUMPTION

Lavatories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .407.2

Showerhead & body sprays . . . . . . . . . . . .408.2, 408.3

Water closets . . . . . . . . . . . . . . . . . . . . . . . . . . . . .411.2

WATER HAMMER ARRESTORS . . . . . . . . . .225.0, 609.11

WATER HEATERS . . . . . . . . . . . . . . . . . . . . . . . .Chapter 5

Access . . . . . . . . . . . . . . . . . . . . . . . .504.3.1, 507.13.2,

507.25, 508.4

Approval requirements . . . . . . . . . . . . . . . . . . . . . .501.1 Approved standards . . . . . .Table 501.1(1), 505.3, 505.4 Clearances. . . . . . . . . . . . . . . . . . . . . . 504.3 – 504.3.2,

508.1, 508.2.1

Combustion air required . . . . . . . . . . . . . . . . . . . .506.0

Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . .604.13

Dual purpose, definition . . . . . . . . . . . . . . . . . . . .225.0

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .225.0

Garages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .507.13 Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .503.2

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .507.0

Location . . . . . . . . . . . . . . . . . . .504.1, 507.12 – 507.15
CPC § 54-2018 High relevance — show source text
Clearance for unlisted water heaters shall be not less than 12 inches (305 mm) on all sides. Combustible floors under unlisted water heaters shall be protected in an approved manner. {NFPA 54-2018:10.27.2.2} 504.4 Pressure-Limiting Devices. A water heater installation shall be provided with overpressure protection using an approved, listed device installed in accordance with the terms of its listing and the manufacturer’s installation instructions. Pressure relief devices shall have a pressure setting greater than the water service pressure and not exceed 150 psi (1034 kPa) as required in Section 608.4. 504.5 Temperature Limiting Devices. A water heater installation or a hot water storage vessel installation shall be provided with overtemperature protection by means of an approved, listed device installed in accordance with the terms of its listing and the manufacturer’s installation instructions. {NFPA 54:10.26.5} 504.6 Temperature, Pressure, and Vacuum Relief Devices. Temperature, pressure, and vacuum relief devices or combinations thereof, and automatic gas shutoff devices shall be installed in accordance with the terms of their listings and the manufacturer’s installation instructions. A shutoff valve shall not be placed between the relief valve and the water heater or on discharge pipes between such valves and the atmosphere. The hourly British thermal units (Btu) (kW•h) discharge capacity or the rated steam relief capacity of the device shall be not less than the input rating of the water heater. {NFPA 54:10.26.6} Discharge piping shall be installed in accordance with Section 608.5.

504.7 Lead Content. Water heaters shall comply with the lead content requirements of Section 604.2.

505.0 Oil-Burning and Other Water Heaters. 505.1 Water Heaters. Water heaters deriving heat from fuels or types of energy other than gas shall comply with the standards referenced in Table 501.1(1), Section 505.3, or Section 505.4. Vents or chimneys for such appliances shall be of approved types. An adequate supply of air for combustion and for adequate ventilation of heater rooms or compartments shall be provided. Each such appliance shall be installed in a

location approved by the Authority Having Jurisdiction and local and state fire-prevention agencies. 505.2 Safety Devices. Storage-type water heaters and hot water boilers deriving heat from fuels or types of energy other than gas, shall be provided with, in addition to the primary temperature controls, an over-temperature safety protection device that complies with and is installed in accordance with nationally recognized applicable standards for such devices and a combination temperature and pressure-relief valve.

505.3 Oil-Fired Water Heaters. Oil-fired water heaters

shall be installed in accordance with NFPA 31.

505.4 Indirect-Fired Water Heaters. Indirect-fired water heaters shall be in accordance with the applicable sections of the ASME Boiler and Pressure Vessel Code or shall comply with one of the other applicable standards shown in Table 501.1(1). Each water heater shall bear a label in accordance with ASME requirements, or an approved testing agency, certifying and attesting that such an appliance has been tested, inspected and meets the requirements of the applicable standards or code. 505.4.1 Single-Wall Heat Exchanger. An indirectfired water heater that incorporates a single-wall heat exchanger shall be in accordance with the following requirements:
CPC § 501.1 High relevance — show source text
Table 501.1(1) Water Heaters . . . . . . . . . . . . . . . .83

501.2 California Energy Code Water Heating System Requirements . . . . . . . . . . . . . . . . .83

502.0 Permits . . . . . . . . . . . . . . . . . . . . . .83

502.1 General . . . . . . . . . . . . . . . . . . . . . .83

503.0 Inspection . . . . . . . . . . . . . . . . . . . .83

503.1 Inspection of Chimneys or Vents . . .83

503.2 Final Water Heater Inspection . . . .83

504.0 Water Heater Requirements . . . . . .83

504.1 Location . . . . . . . . . . . . . . . . . . . . .83

Table 501.1(2) First Hour Rating . . . . . . . . . . . . . .83

504.2 Vent . . . . . . . . . . . . . . . . . . . . . . . .84

504.3 Clearance . . . . . . . . . . . . . . . . . . . .84

504.4 Pressure-Limiting Devices . . . . . . .84

504.5 Temperature-Limiting Devices . . . .84

504.6 Temperature, Pressure, and Vacuum Relief Devices . . . . . . . . .84

504.7 Lead Content . . . . . . . . . . . . . . . . .84

505.0 Oil-Burning and Other Water Heaters . . . . . . . . . . . . . . . . . . . . . .84

505.1 Water Heaters . . . . . . . . . . . . . . . .84

505.2 Safety Devices . . . . . . . . . . . . . . . .84

505.3 Oil-Fired Water Heaters . . . . . . . . .84

505.4 Indirect-Fired Water Heaters . . . . .84

506.0 Air for Combustion and

Ventilation . . . . . . . . . . . . . . . . . . . .84

506.1 General . . . . . . . . . . . . . . . . . . . . . .84

506.2 Indoor Combustion Air . . . . . . . . . .85

506.3 Indoor Opening Size and Location . . . . . . . . . . . . . . . . . . . . .85

506.4 Outdoor Combustion Air . . . . . . . . .85

506.5 Combination Indoor and

Outdoor Combustion Air . . . . . . . . .87

506.6 Engineered Installations . . . . . . . . .87

506.7 Mechanical Combustion Air Supply . . . . . . . . . . . . . . . . . . . . . . .87

506.8 Louvers, Grilles, and Screens . . . .87

506.9 Combustion Air Ducts . . . . . . . . . . .87

507.0 Appliance and Equipment Installation Requirements . . . . . . . .88

507.1 Dielectric Insulator . . . . . . . . . . . . .88
CPC § 916.4 High relevance — show source text
vent instead of the rear wall of the unit heater. A unit

heater listed for reduced clearances shall be installed in accordance with its listing and the manufacturer’s installation instructions.

(2) Floor-mounted-type unit heaters installed on combustible floors shall be listed for such installation.

(3) Combustible floors under unlisted floor-mounted unit heaters shall be protected in an approved man ner.

(4) Clearances for servicing shall be in accordance with the manufacturer’s instructions.

916.4 Combustion and Circulating Air. Combustion and circulating air shall be provided in accordance with Section 701.0. [NFPA 54:10.24.4]

916.5 Ductwork. A unit heater shall not be attached to a warm air duct system unless listed and marked for such installation. [NFPA 54:10.24.5] 916.6 Installation in Commercial Garages and Air- craft Hangars. Unit heaters installed in garages for more than three motor vehicles or in aircraft hangars shall be installed in accordance with Section 303.11 and Section 303.12. [NFPA 54:10.24.6]

916.7 Oil-Fired Unit Heaters. Oil-fired unit heaters shall comply with UL 731 and installed in accordance with the manufacturer’s installation instructions.

917.0 Food Service Appliance, Floor-Mounted. 917.1 Application. Floor-mounted food service appliances shall be listed in accordance with ANSI Z83.11/CSA 1.8.

[NFPA 54:10.11.1] 917.2 Clearance for Listed Appliances. Floor-mounted food service appliances, such as ranges for hotels and restaurants, deep fat fryers, unit broilers, kettles, steam cookers, steam generators, and baking and roasting ovens, shall be installed not less than 6 inches (152 mm) from combustible material except that at least a 2 inch (51 mm) clearance shall be maintained between a draft hood and combustible material. Floor-mounted food service appliances listed for installation at lesser clearances shall be installed in accordance with its listing and the manufacturer’s installation instructions. Appliances designed and marked, “For use only in noncombustible locations,” shall not be installed elsewhere. [NFPA 54:10.11.2] 917.3 Mounting on Combustible Floors. Floor-mounted food service appliances that are listed specifically for installation on floors constructed of combustible material shall be permitted to be installed on combustible floors in accordance with its listing and the manufacturer’s installation instructions. [NFPA 54:10.11.3.1]

917.3.1 Not Listed for Mounting on Combustible Floors. Floor-mounted food service appliances that are not listed for installation on a combustible floor shall be

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such as to interfere with combustion air and accessibility. Unlisted room heaters shall be installed with clearances from combustible material not less than the following:

(1) Circulating type room heaters having an outer jacket surrounding the combustion chamber, arranged with openings at top and bottom so that air circulates between the inner and outer jacket, and without openings in the outer jacket to permit direct radiation, shall have clearance at sides and rear of not less than 12 inches (305 mm).

CPC § 4.1 Medium relevance — show source text

Access
and clearance shall be in accordance with the
manufacturer’s instructions, and not less than
a 12 inch clearance at the bottom for mainte-
nance. May need platform/ladder for test and
repair. May discharge water.
Installation includes a fire protection system
and is designed to operate under continuous
pressure conditions.| |Reduced Pressure Princi-
ple Backflow Prevention
Assembly (two independ-
ently acting loaded check
valves, a differential pres-
sure relief valve and
means for field testing)|ASSE 1013;
AWWA C511;
CSA B64.4 or
CSA B64.4.1|X|X|X|X|Horizontal unless otherwise listed. Access
and clearance shall be in accordance with the
manufacturer’s instructions, and not less than
a 12 inch clearance at the bottom for mainte-
nance. May need platform/ladder for test and
repair. May discharge water.| |Spill-Resistant Pressure
Vacuum Breaker (single
check valve with air
inlet vent and means of
field testing)|ASSE 1056|X|––|X|––|Upright position. Minimum of 12 inches or
listed distance above all downstream piping
and flood-level rim of receptor.5| |Vacuum breaker wall
hydrants, hose bibbs,
freeze resistant, auto-
matic draining type|ASSE 1019 or
CSA B64.2.1.1|X|––|X|––|Installation includes wall hydrants and hose
bibbs. Such devices are not for use under con-
tinuous pressure conditions (means of shutoff
downstream of device is prohibited).4,5|

For SI units: 1 inch = 25.4 mm

Notes: 1 See the description of devices and assemblies in this chapter. 2 Installation in pit or vault requires previous approval by the Authority Having Jurisdiction. 3 Refer to the general and specific requirement for installation. 4 Not to be subjected to operating pressure for more than 12 hours in a 24-hour period. 5 For deck-mounted and equipment-mounted vacuum breaker, see Section 603.5.13. 6 Shall be installed in accordance with Section 603.5.7.

2025 CALIFORNIA PLUMBING CODE 143

WATER SUPPLY AND DISTRIBUTION

TABLE 603.3.1 MINIMUM AIR GAPS FOR WATER DISTRIBUTION [4]

FIXTURES	WHERE NOT AFFECTED BY SIDEWALLS1 (inches)	WHERE AFFECTED BY SIDEWALLS2 (inches)
Effective openings3 not greater than1⁄2 of an inch in diameter	1	11⁄2
Effective openings3 not greater than3⁄4 of an inch in diameter	11⁄2	21⁄4
Effective openings3 not greater than 1 inch in diameter	2	3
Effective openings3 greater than 1 inch in diameter	Two times the diameter of effective opening	Three times the diameter of effective opening

For SI units: 1 inch = 25.4 mm

CPC § 608.3 Medium relevance — show source text
The expansion tank shall be properly sized, securely fastened to the structure, and installed in accordance with the manufacturer’s installation instructions and listing. Systems designed by a licensed plumbing contractor or registered design professionals shall be permitted to use approved pressure relief valves in lieu of expansion tanks provided such relief valves have a maximum pressure relief setting of 100 psi (689 kPa) or less. 608.3 Expansion Tanks, and Combination Tempera- ture and Pressure-Relief Valves. A water system provided with a check valve, backflow preventer, or other normally closed device that prevents dissipation of building pressure back into the water main, independent of the type of water heater used, shall be provided with an approved, listed, and adequately sized expansion tank or other approved device having a similar function to control thermal expansion. Prepressurized water expansion tanks shall comply with IAPMO/ANSI Z1088. Such expansion tank or other approved device shall be installed on the building side of the check valve, backflow preventer, or other device and shall be sized, securely fastened to the structure, and installed in accordance with the manufacturer’s installation instructions.

A water system containing storage water heating equipment shall be provided with an approved, listed, adequately sized combination temperature and pressure-relief valve, except for listed nonstorage instantaneous heaters having an inside diameter of not more than 3 inches (80 mm). Each such approved combination temperature and pressure-relief valve shall be installed on the water-heating device in an approved location based on its listing requirements and the manufacturer’s installation instructions. Each such combination temperature and pressure-relief valve shall be provided with a drain in accordance with Section 608.5.

Exception: An expansion tank shall not be required for an instantaneous non-storage water heater. 608.4 Pressure Relief Valves. Each pressure relief valve shall be an approved automatic type with drain, and each such relief valve shall be set at a pressure of not more than 150 psi (1034 kPa). No shutoff valve shall be installed between the relief valve and the system. 608.5 Discharge Piping. The discharge piping serving a temperature relief valve, pressure relief valve, or combination of both shall have no valves, obstructions, or means of isolation and be provided with the following:

(1) Not less than the size of the valve outlet and shall discharge full size to the flood level of the area receiving the discharge and pointing down.

(2) Materials shall be rated at not less than the operating temperature of the system and approved for such use or shall comply with ASME A112.4.1.

(3) Discharge pipe shall discharge independently by gravity through an air gap into the drainage system or outside of the building with the end of the pipe not exceeding 2 feet

154 2025 CALIFORNIA PLUMBING CODE

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

WATER SUPPLY AND DISTRIBUTION

(610 mm) and not less than 6 inches (152 mm) above the ground and pointing downwards.

(4) Discharge in such a manner that does not cause personal injury or structural damage. (5) No part of such discharge pipe shall be trapped or subject to freezing. (6) The terminal end of the pipe shall not be threaded. (7) Discharge from a relief valve into a water heater pan shall be prohibited. (8) The discharge termination point shall be readily observable.
CPC § 422.1 Medium relevance — show source text
422.1 Fixture Count . . . . . . . . . . . . . . . . .67

422.2 Separate Facilities . . . . . . . . . . . . .68

422.3 Fixture Requirements for Special Occupancies . . . . . . . . . . .68

422.4 Toilet Facilities Serving Employees and Customers . . . . . .68

422.5 Toilet Facilities for Workers . . . . . .69

422.6 Water Closet Compartment . . . . . .69

422.7 Urinal Partitions . . . . . . . . . . . . . . .69

422.8 Cosmetology . . . . . . . . . . . . . . . . .69

422.9 Cosmetology Establishments . . . . .69

422.10 Commissaries Serving Mobile Food Preparation Units . . . . . . . . .69

422.11 Employee Lavatories in Food Establishments . . . . . . . . . . .69

Table 422.1 Minimum Plumbing Facilities . . . . .70

Table 4-1 Occupant Load Factor

[BSC and DSA-SS] . . . . . . . . . . . .75

Table 4-2 Minimum Plumbing Facilities

[OSHPD 1, 2, 3, 4 & 5] . . . . . . . . .76

CHAPTER 5 WATER HEATERS . . . . . . . . . . . .81

501.0 General . . . . . . . . . . . . . . . . . . . . . .83

501.1 Applicability . . . . . . . . . . . . . . . . . . .83

Table 501.1(1) Water Heaters . . . . . . . . . . . . . . . .83

501.2 California Energy Code Water Heating System Requirements . . . . . . . . . . . . . . . . .83

502.0 Permits . . . . . . . . . . . . . . . . . . . . . .83

502.1 General . . . . . . . . . . . . . . . . . . . . . .83

503.0 Inspection . . . . . . . . . . . . . . . . . . . .83

503.1 Inspection of Chimneys or Vents . . .83

503.2 Final Water Heater Inspection . . . .83

504.0 Water Heater Requirements . . . . . .83

504.1 Location . . . . . . . . . . . . . . . . . . . . .83

Table 501.1(2) First Hour Rating . . . . . . . . . . . . . .83

504.2 Vent . . . . . . . . . . . . . . . . . . . . . . . .84

504.3 Clearance . . . . . . . . . . . . . . . . . . . .84

504.4 Pressure-Limiting Devices . . . . . . .84

504.5 Temperature-Limiting Devices . . . .84

504.6 Temperature, Pressure, and Vacuum Relief Devices . . . . . . . . .84

504.7 Lead Content . . . . . . . . . . . . . . . . .84

Frequently asked questions

Do I always need a pan under the water heater?

If the water heater is located in an attic or in/over an assembly where a leak would cause damage, yes — a watertight, corrosion‑resistant pan meeting § 507.5 is required.

What if the manufacturer’s instructions say less clearance than 12 inches?

For listed appliances, follow the listing/manufacturer’s instructions; listed clearances control for listed units as described in § 504.3.1. For unlisted units, the code requires 12 in on all sides per § 504.3.2.

Can the T&P valve discharge go into the pan?

No. Discharge from a relief valve into a drainage pan is prohibited by § 507.5 (4) and discharge piping rules in § 608.5.

How big must the pan drain be and where must it terminate?

The pan drain must be at least 3/4 in (20 mm) diameter and terminate to an approved location with the terminating end readily visible, per § 507.5 (1).

Is 30 inches of clearance always required in front of the heater?

The code’s default service/work space is 30 in (depth, width, height) per § 507.25, unless another section or the appliance listing specifies otherwise.

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California Plumbing Code