Section 160.4 — MANDATORY REQUIREMENTS FOR WATER-HEATING

(a) Water-heating recirculation loops serving multiple dwelling units shall meet the requirements of Section 110.3(c)4.

(b) Solar water-heating systems and collectors shall be certified and rated by the Solar Rating and Certification Corporation (SRCC), the International Association of Plumbing and Mechanical Officials, Research and Testing (IAPMO R&T), or a listing agency that is approved by the Executive Director.

(c) Instantaneous water heaters with an input rating greater than 6.8 kBTU/hr (2kW) shall meet the requirements of Section 110.3(c)6.

(d) Commercial boilers

Combustion air positive shut-off shall be provided on all newly installed boilers as follows: A. All boilers with an input capacity of 2.5 MMBtu/h (2,500,000 Btu/h) and above, in which the boiler is designed to operate with a nonpositive vent static pressure. B. All boilers where one stack serves two or more boilers with a total combined input capacity per stack of 2.5 MMBtu/h (2,500,000 Btu/h).
Boiler combustion air fans with motors 10 horsepower or larger shall meet one of the following for newly installed boilers: A. The fan motor shall be driven by a variable speed drive, or B. The fan motor shall include controls that limit the fan motor demand to no more than 30 percent of the total design wattage at 50 percent of design air volume.
Newly installed boilers with an input capacity 5 MMBtu/h (5,000,000 Btu/h) and greater shall maintain excess (stack-gas) oxygen concentrations at less than or equal to 5.0 percent by volume on a dry basis over firing rates of 20 percent to 100 percent. Combustion air volume shall be controlled with respect to firing rate or flue gas oxygen concentration. Use of a common gas and combustion air control linkage or jack shaft is prohibited. Exception to Section 160.4(d)3: Boilers with steady state full-load thermal combustion efficiency 90 percent or higher.

(e) Pipe insulation

All piping for multifamily domestic hot water systems shall be insulated and meet the applicable requirements in Items 1 through 3 below:

General requirements. A. The first 8 feet of inlet cold water piping from the storage tanks, including piping between a storage tank and a heat trap, shall be insulated. B. Insulation on the piping and domestic hot water system appurtenances shall be continuous. C. Pipe supports, hangers, and pipe clamps shall be attached on the outside of rigid pipe insulation to prevent thermal bridges. D. All pipe insulation seams shall be sealed. E. Insulation for pipe elbows shall be mitered, preformed, or site fabricated with PVC covers. F. Insulation for tees shall be notched, preformed, or site fabricated with PVC covers.

G. Extended stem isolation valves shall be installed.

H. All plumbing appurtenances on hot water piping from a heating source to heating plant, at the heating plant, and distribution supply and return piping shall be insulated to meet the following requirements: i. Where the outer diameter of the appurtenance is less than the outer diameter of the insulated pipe that it is attached to, the appurtenance shall be insulated flush with the insulation surrounding the pipe. ii. Where the outer diameter of the appurtenance is greater than the outer diameter of the insulated pipe that it is attached to, the appurtenance shall be insulated with a minimum thickness of 1 inch. iii. The insulation shall be removable and re-installable to ensure maintenance or replacement services can be completed. iv. Valves shall be fully functional without impediment from the insulation.

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

MULTIFAMILY BUILDINGS—MANDATORY REQUIREMENTS

Insulation thickness. All piping for multifamily domestic hot water systems shall meet the insulation thickness requirements specified in Table 160.4-A. A. For insulation conductivity in the range shown in Table 160.4-A for the applicable fluid temperature range, the insulation shall have the applicable minimum thickness or R -value shown in Table 160.4-A. B. If the insulation conductivity falls outside the range provided in Table 160.4-A applicable fluid temperature range, the insulation shall meet a minimum R -value as indicated in Table 160.4-A. Or, it can have a thickness determined using Equation 160.4-A.

(Equation 160.4-A)

[-] k [-]

T = PR 1 + ------ PRt – 1

TABLE 160.4-A—PIPE INSULATION THICKNESS—MULTIFAMILY DOMESTIC HOT WATER

FLUID OPERATING TEMPERATURE RANGE (°F)	INSULATION CONDUCTIVITY	INSULATION CONDUCTIVITY		NOMINAL PIPE DIAMETER (in inches)	NOMINAL PIPE DIAMETER (in inches)	NOMINAL PIPE DIAMETER (in inches)	NOMINAL PIPE DIAMETER (in inches)	NOMINAL PIPE DIAMETER (in inches)
FLUID OPERATING TEMPERATURE RANGE (°F)	Conductivity (in Btu·in/h·ft2· °F)	Mean Rating Temperature (°F)	Mean Rating Temperature (°F)	< 1	1 to < 1.5	1.5 to < 4	4 to < 8	8 and larger
Multifamily Domestic Hot Water Systems	Multifamily Domestic Hot Water Systems	Multifamily Domestic Hot Water Systems		Minimum Pipe Insulation Required (Thickness in inches or_R-_value)	Minimum Pipe Insulation Required (Thickness in inches or_R-_value)	Minimum Pipe Insulation Required (Thickness in inches or_R-_value)	Minimum Pipe Insulation Required (Thickness in inches or_R-_value)	Minimum Pipe Insulation Required (Thickness in inches or_R-_value)
105–1401	0.22–0.28	100	Inches	1.0	1.5	2.0	2.0	2.0
105–1401	0.22–0.28	100	_R-_value	R7.7	R12.5	R16	R12.5	R11
1. Multifamily and hotel/motel domestic hot water systems with water temperature above 140°F shall use the row in Table 120.3-A for the applicable water temperature.

Insulation protection. Pipe insulation shall be protected from damage due to sunlight, moisture, equipment maintenance and wind. Protection shall, at minimum, include the following: A. Pipe and appurtenance insulation exposed to weather shall be protected by a cover suitable for outdoor service. The cover shall be water retardant and provide shielding from solar radiation that can cause degradation of the material. Appurtenance insulation covers shall be removable and able to be reinstalled. Adhesive tape shall not be used to provide this protection. B. Pipe insulation covering chilled water piping and refrigerant suction piping located outside the conditioned space shall include, or be protected by, a Class I or Class II vapor retarder. All penetrations and joints shall be sealed. C. Pipe insulation buried below grade must be installed in a waterproof and noncrushable casing or sleeve.

NOTE: Authority: Sections 25213, 25218, 25218.5, 25402 and 25402.1, Public Resources Code . Reference: Sections 25007, 25008, 25218.5, 25310, 25402, 25402.1, 25402.4, 25402.5, 25402.8 and 25943, Public Resources Code .