501.1 Applicability — 2025 California Plumbing Code

The regulations of this chapter shall govern the construction, location, and installation of fuel-burning and other types of water heaters heating potable water, together with chimneys, vents, and their connectors. The minimum capacity for storage water heaters shall be in accordance with the first-hour rating listed in Table 501.1(2). A list of accepted water heater appliance standards is referenced in Table 501.1(1). Listed appliances shall be installed in accordance with the manufacturer’s installation instructions. Unlisted water heaters shall be permitted in accordance with Section 504.3.2.

Water heaters shall be installed in accordance with the

manufacturer’s installation instructions. The final installation shall be approved by the Authority Having Jurisdiction.

TABLE 501.1(1)

WATER HEATERS

TYPE*	STANDARD
Electric, Household Storage	UL 174
Oil-Fired Storage Tank	UL 732
Gas-Fired, 75 000 Btu/h or less, Storage	CSA/ANSI Z21.10.1/CSA 4.1
Gas-Fired, Above 75 000 Btu/h, Storage and Instantaneous	CSA/ANSI Z21.10.3/CSA 4.3
Electric, Commercial Storage	UL 1453
Solid Fuel-Fired	UL 2523
Electric Instantaneous	UL 499

For SI units: 1000 British thermal units per hour = 0.293 kW

Dual purpose water heaters shall be installed in accordance with this code and the manufacturer’s installation instructions.

TABLE 501.1(2) FIRST HOUR RATING [1]

Number of Bathrooms	1 to 1.5			2 to 2.5				3 to 3.5
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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