What pipe insulation and thickness rules apply to multifamily domestic hot water systems?

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

• § 160.4 High relevance — show source text

  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:

  1. 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.

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

  MULTIFAMILY BUILDINGS—MANDATORY REQUIREMENTS

  2. 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

  [-] k [-]

  T = PR  1 + ------ PRt  – 1

  |TABLE 160.

• § 160.4 High relevance — show source text

  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.

  2025 CALIFORNIA ENERGY CODE 223

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

  MULTIFAMILY BUILDINGS—MANDATORY REQUIREMENTS

  2. 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

  [-] k [-]

  T = PR  1 + ------ PRt  – 1

  TABLE 160.4-A—PIPE INSULATION THICKNESS—MULTIFAMILY DOMESTIC HOT WATER	Col2	Col3	Col4	Col5	Col6	Col7	Col8	Col9
  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.

• § 412.2 High relevance — show source text

  Exception: Flushometer tailpiece trap primers in accordance with ASSE 1044 or IAPMO PS 76.

  L 412.2 Drainage Type Trap Seal Primer Devices. Drainage type trap seal primer devices shall not be limited in the amount of water they discharge.

  L 413.0 Vehicle Wash Facilities.

  L 413.1 Automatic. The maximum make-up water use for automobile washing shall not exceed 40 gallons (151 L) per vehicle for in-bay automatic car washes and 35 gallons (132 L) for conveyor and express type car washes. L 413.2 Self-Service. Spray wands and foamy brushes shall use not more than 3.0 gpm (0.19 L/s). L 413.3 Reverse Osmosis. Spot-free reverse osmosis discharge (reject) water shall be recycled. L 413.4 Towel Ringers. Towel ringers shall have a positive shutoff valve. Spray nozzles shall be replaced annually.

  Exception: Bus and large commercial vehicle washes are exempt from the requirements of this section.

  L 501.0 Water Heating Design, Equipment, and Instal- lation.

  L 501.1 Scope. The provisions of this section shall establish the means of conserving potable and nonpotable water and energy associated with the generation and use of hot water in a building. This includes provisions for the hot water distribution system, which is the portion of the potable water distribution system between a water heating device and the plumbing fixtures, including dedicated return piping and appurtenances to the water heating device in a recirculation system. L 501.2 Insulation. Hot water supply and return piping shall be thermally insulated. The wall thickness of the insulation shall be equal to the nominal diameter of the pipe up to 2 inches (50 mm). The wall thickness shall be not less than 2 inches (51 mm) for nominal pipe diameters exceeding 2 inches (50 mm). The conductivity of the insulation [k-factor (Btu•in/(h•ft [2] - °F))], measured radially, shall not be more than 0.28 [Btu•in/(h•ft [2] - °F)] [0.04 W/(m•K)]. Hot water piping to be insulated shall be installed such that insulation is continuous. Pipe insulation shall be installed to within [1] ⁄ 4 of an inch (6.4 mm) of appliances, appurtenances, fixtures, structural members, or a wall where the pipe passes through to connect to a fixture within 24 inches (610 mm).

  2025 CALIFORNIA PLUMBING CODE 507

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

  APPENDIX L

  Exceptions:

  (1) Where the hot water pipe is installed in a wall that is not of a width to accommodate the pipe and insulation, the insulation thickness shall be permitted to have the maximum thickness that the wall is capable of accommodating and not less than [1] ⁄ 2 of an inch (12.7 mm) thick.

  (2) Hot water supply piping exposed under sinks, lavatories, and similar fixtures.

  L 501.2.1 Pipe Supports. Pipe supports shall be installed on the outside of the pipe insulation.

• § 609.11 High relevance — show source text

  (b) Where occupancy is delayed four weeks after disin- fection, disinfection and flushing shall again be com- pleted. 609.11 Water Hammer. [Not adopted by HCD] Building water supply systems where quick-acting valves are installed shall be provided with water hammer arrester(s) to absorb high pressures resulting from the quick closing of these valves. Water hammer arresters shall be approved mechanical devices that comply with ASSE 1010 or PDI-WH 201 and shall be installed as close as possible to quick-acting valves.

  609.11.1 Mechanical Devices. Where listed mechanical devices are used, the manufacturer’s specifications as to location and method of installation shall be followed.

  609.12 Pipe Insulation. Insulation of domestic hot water piping shall be in accordance with Section 609.12.1 and Section 609.12.2.

  609.12.1 Insulation Requirements. Domestic hot water piping shall be insulated. 609.12.2 Pipe Insulation Wall Thickness. Hot water pipe insulation shall have a minimum wall thickness of not less than the diameter of the pipe for a pipe up to 2 inches (50 mm) in diameter. Insulation wall thickness shall be not less than 2 inches (51 mm) for a pipe of 2 inches (50 mm) or more in diameter. Exceptions: (1) Piping that penetrates framing members shall not be required to have pipe insulation for the distance of the framing penetration. (2) Hot water piping between the fixture control valve or supply stop and the fixture or appliance shall not be required to be insulated. 609.12.3 California Energy Code Pipe Insulation Requirements. [CEC] See California Energy Code Sec- tions 150.0(j)2 and 120.3(c) for pipe insulation require- ments based on fluid temperature and pipe diameter – for domestic hot water piping. The California Energy Code requires that piping that penetrates metal framing shall use grommets, plugs, wrapping or other insulating mate- rial to assure that no contact is made with the metal fram- ing. The California Energy Code also requires that insulation shall abut securely against all framing mem- bers, and places conditions on when installed wall or attic insulation that surrounds installed piping can be consid- ered to provide pipe insulation meeting requirements.

  610.0 Size of Potable Water Piping. 610.1 Size. The size of each water meter and each potable water supply pipe from the meter or other source of supply to the fixture supply branches, risers, fixtures, connections, outlets, or other uses shall be based on the total demand and shall be determined according to the methods and procedures outlined in this section. Water piping systems shall be designed to ensure that the maximum velocities allowed by the code and the applicable standard are not exceeded.

  610.2 Pressure Loss. Where a water filter, water softener, backflow prevention device, tankless water heater, or similar device is installed in a water supply line, the pressure loss through such devices shall be included in the pressure loss calculations of the system, and the water supply pipe and meter shall be adequately sized to provide for such a pressure loss.

• § 160.3 High relevance — show source text

  (c) Fluid distribution systems; common area space-conditioning systems. Multifamily buildings shall comply with the applicable requirements of Section 160.3(a)1. Multifamily common areas shall comply with the applicable requirements of Sections 160.3(a)2A through 160.3(a)2J.

  1. Pipe insulation . Multifamily buildings shall comply with the applicable requirements of Sections 160.3(c)1A through 160.3(c)1D. A. General requirements. The piping conditions listed below for space-conditioning systems with fluid normal operating temperatures listed in Table 160.3-D shall have at least the amount of insulation specified in Section 160.3(c)1D: i. Space cooling systems. All refrigerant suction, chilled water and brine fluid distribution systems. ii. Space heating systems. All refrigerant suction, steam, steam condensate and hot water fluid distribution systems. Exception to Section 160.3(c)1Aii: Heat pumps refrigerant vapor line shall be installed with a minimum of 0.75-inch-thick or R-6.0 insulation. No insulation is required on the refrigerant liquid line. B. Insulation conductivity shall be determined in accordance with ASTM C335 at the mean temperature listed in Table 160.3-D, and shall be rounded to the nearest [1] / 100 Btu-inch per hour per square foot per °F. Fluid distribution systems include all elements that are in series with the fluid flow, such as pipes, pumps, valves, strainers, coil u-bends and air separators, but not including elements that are not in series with the fluid flow, such as expansion tanks, fill lines, chemical feeders and drains.

  C. Insulation protection. Pipe insulation shall be protected from damage due to sunlight, moisture, equipment maintenance and wind. Protection shall, at minimum, include the following: i. Pipe 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. Adhesive tape shall not be used to provide this protection. ii. 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.

  iii. Pipe insulation buried below grade must be installed in a waterproof and noncrushable casing or sleeve.

  D. Insulation thickness.

  i. For insulation with a conductivity in the range shown in Table 160.3-D for the applicable fluid temperature range, the insulation shall have the applicable minimum thickness or R- value shown in Table 160.3-D. ii. For insulation with a conductivity outside the range shown in Table 160.3-D for the applicable fluid temperature range, the insulation shall have a minimum R- value shown in Table 160.3-D or thickness as calculated with Equation 160.3-A:

  (Equation 160.3-A)

  T = PR  1 + ------ PRt 

  K

  [-] k [-] = PR  1 + ------ t  – 1

  where:

  T = Minimum insulation thickness for material with conductivity K, inches. PR = Pipe actual outside radius, inches.

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

• § 120.3 High relevance — show source text

  3-A for the applicable water temperature.|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.|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.|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.|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.|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.|

  3. 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 .

  SECTION 160.5—MANDATORY LIGHTING REQUIREMENTS FOR INDOOR AND OUTDOOR SPACES

  The design and installation of all lighting systems and equipment in multifamily buildings within the scope of Section 100.0(a) shall comply with the applicable provisions of Section 160.5. All functional areas except dwelling units and common living areas shall comply with the applicable requirements of Sections 160.5(b) through 160.5(e).

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  where:

  T = Minimum insulation thickness for material with conductivity K, inches. PR = Pipe actual outside radius, inches. t = Insulation thickness from Table 160.4-A, inches.

  K = Conductivity of alternate material at the mean rating temperature indicated in Table 160.4-A for the applicable fluid temperature range, in Btu-inch per hour per square foot per °F. k = The lower value of the conductivity range listed in Table 160.4-A for the applicable fluid temperature range, Btu-inch per hour per square foot per °F. C. Insulation conductivity shall be determined in accordance with ASTM C335 at the mean temperature listed in Table 160.4-A and shall be rounded to the nearest 1/100 Btu-inch per hour per square foot per °F.

• § 90.1 High relevance — show source text

  [ASHRAE 90.1: TABLE 6.8.3-2]

  FLUID OPERATING TEMPERATURE RANGE (°F) AND USAGE	INSULATION CONDUCTIVITY	Col3	NOMINAL PIPE SIZE OR TUBE SIZE (inches)	Col5	Col6	Col7	Col8
  FLUID OPERATING TEMPERATURE RANGE (°F) AND USAGE	CONDUCTIVITY Btu•inch/(h•f2•°F)	MEAN RATING TEMPERATURE °F	<1	1 to <11_/_2	11_/_2 to <4	4 to <8	≥8
  FLUID OPERATING TEMPERATURE RANGE (°F) AND USAGE	CONDUCTIVITY Btu•inch/(h•f2•°F)	MEAN RATING TEMPERATURE °F	INSULATION THICKNESS (inches)	INSULATION THICKNESS (inches)	INSULATION THICKNESS (inches)	INSULATION THICKNESS (inches)	INSULATION THICKNESS (inches)
  40 to 60	021 to 0.27	75	0.5	0.5	1.0	1.0	1.0
  <40	0.20 to 0.26	50	0.5	1.0	1.0	1.0	1.5

  For SI units: °C = (°F-32)/1.8, 1 inch = 25 mm, 1 British thermal unit inch per hour square foot degree Fahrenheit = [0.1 W/(m•k)]

  Notes: 1 For insulation outside the stated conductivity range, the minimum thickness ( T ) shall be determined as follows: T = r {(1 + t/r ) [K/k ] – 1}

  Where:

  T = minimum insulation thickness (inches). r = actual outside radius of pipe (inches). t = insulation thickness listed in this table for applicable fluid temperature and pipe size. K = conductivity of alternate material at mean rating temperature indicated for the applicable fluid temperature [Btu • inch/(h • ft [2] • °F)] [W/(m•K)]. k = the upper value of the conductivity range listed in this table for the applicable fluid temperature. 2 These thicknesses are based on energy efficiency considerations only. Issues such as water, vapor permeability, or surface condensation require vapor retarders or additional insulation. 3 For direct-buried cooling system piping, insulation is not required. 4 Table E 503.7.3(2) is based on steel pipe. Nonmetallic pipes schedule 80 thickness or less shall use the table values. For other nonmetallic pipes having thermal resistance more than that of steel pipe, reduced insulation thicknesses are permitted where documentation is provided showing that the pipe with the proposed insulation has no more heat transfer per foot (mm) than a steel pipe of the same size with the insulation thickness shown in Table E 503.7.3(2).

• § 1.9 High relevance — show source text

  9| |7 to 8|R-1.9|R-1.9|R-1.9|

  Notes: 1 Insulation R-values, measured in [°F•h•ft 2 /(Btu•in)] [(m•K)/W], are for the insulation as installed and do not include film resistance. The required minimum thicknesses do not consider water vapor transmission and possible surface condensation. Where portions of the building envelope are used as a plenum enclosure, building envelope insulation shall be as required by the most restrictive condition of Section E 503.4.7.1 or ASHRAE 90.1, depending on whether the plenum is located in the roof, wall, or floor. Insulation resistance measured on a horizontal plane in accordance with ASTM C518 at a mean temperature of 75°F (24°C) at the installed thickness. 2 Includes attics above insulated ceilings, parking garages and crawl spaces. 3 Includes return air plenums, with or without exposed roofs above. 4 Return ducts in this duct location do not require insulation.

  TABLE E 503.7.3(1) MINIMUM PIPE INSULATION THICKNESS FOR HEATING AND HOT WATER SYSTEMS [1, 2, 3, 4, 5]

  (STEAM, STEAM CONDENSATE, HOT WATER HEATING, AND DOMESTIC WATER SYSTEMS)

  [ASHRAE 90.1: TABLE 6.8.3-1]

  FLUID OPERATING TEMPERATURE RANGE (F°) AND USAGE	INSULATION CONDUCTIVITY	Col3	NOMINAL PIPE SIZE OR TUBE SIZE (inches)	Col5	Col6	Col7	Col8
  FLUID OPERATING TEMPERATURE RANGE (F°) AND USAGE	CONDUCTIVITY Btu•inch/(h•ft2•°F)	MEAN RATING TEMPERATURE °F	<1	1 to <11_/_2	11_/_2 to <4	4 to <8	≥8
  FLUID OPERATING TEMPERATURE RANGE (F°) AND USAGE	CONDUCTIVITY Btu•inch/(h•ft2•°F)	MEAN RATING TEMPERATURE °F	INSULATION THICKNESS (inches)	INSULATION THICKNESS (inches)	INSULATION THICKNESS (inches)	INSULATION THICKNESS (inches)	INSULATION THICKNESS (inches)
  >350	0.32 to 0.34	250	4.5	5.0	5.0	5.0	5.0
  251 to 350	0.29 to 0.32	200	3.0	4.0	4.5	4.5	4.5
  201 to 250	0.27 to 0.30	150	2.5	2.5	2.5	3.0	3.0
  141 to 200	0.25 to 0.29	125	1.5	1.5	2.0	2.0	2.0
  105 to 140	0.22 to 0.28	100	1.

• § 207.6 High relevance — show source text

  TABLE A6.207.6-A—PIPE INSULATION THICKNESS	Col2	Col3	Col4	Col5	Col6	Col7	Col8	Col9
  FLUID TEMPERATUR E RANGE (°F)	CONDUCTIVITY RANGE (in Btu-inch per hour per square foot per °F)	INSULATION MEAN RATING TEMPERATURE (°F)	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)	NOMINAL PIPE DIAMETER (in inches)
  FLUID TEMPERATUR E RANGE (°F)	CONDUCTIVITY RANGE (in Btu-inch per hour per square foot per °F)	INSULATION MEAN RATING TEMPERATURE (°F)	Runouts up to 2	1 and less	1.25-2	2.50-4	5-6	8 and larger
  FLUID TEMPERATUR E RANGE (°F)	CONDUCTIVITY RANGE (in Btu-inch per hour per square foot per °F)	INSULATION MEAN RATING TEMPERATURE (°F)	INSULATION THICKNESS REQUIRED (in inches)	INSULATION THICKNESS REQUIRED (in inches)	INSULATION THICKNESS REQUIRED (in inches)	INSULATION THICKNESS REQUIRED (in inches)	INSULATION THICKNESS REQUIRED (in inches)	INSULATION THICKNESS REQUIRED (in inches)
  Space heating systems (steam, steam condensate and hot water)	Space heating systems (steam, steam condensate and hot water)	Space heating systems (steam, steam condensate and hot water)	Space heating systems (steam, steam condensate and hot water)	Space heating systems (steam, steam condensate and hot water)	Space heating systems (steam, steam condensate and hot water)	Space heating systems (steam, steam condensate and hot water)	Space heating systems (steam, steam condensate and hot water)	Space heating systems (steam, steam condensate and hot water)
  Above 350	0.32-0.34	250	1.5	2.5	2.5	3.0	3.5	3.5
  251-350	0.29-0.31	200	1.5	2.0	2.5	2.5	3.5	3.5
  201-250	0.27-0.30	150	1.0	1.5	1.5	2.0	2.0	3.5
  141-200	0.25-0.29	125	0.5	1.5	1.5	1.5	1.5	1.

• § 6.8 High relevance — show source text

  (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

  1. 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).
  2. 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.
  3. 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:

  1. 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.

• § 1.9 High relevance — show source text

  9| |SUPPLY AND RETURN DUCTS FOR HEATING ONLY|SUPPLY AND RETURN DUCTS FOR HEATING ONLY|SUPPLY AND RETURN DUCTS FOR HEATING ONLY|SUPPLY AND RETURN DUCTS FOR HEATING ONLY| |0 to 1|none|none|none| |2 to 4|R-6|R-6|R-1.9| |5 to 8|R-12|R-6|R-1.9| |SUPPLY AND RETURN DUCTS FOR COOLING ONLY|SUPPLY AND RETURN DUCTS FOR COOLING ONLY|SUPPLY AND RETURN DUCTS FOR COOLING ONLY|SUPPLY AND RETURN DUCTS FOR COOLING ONLY| |0 to 6|R-8|R-6|R-1.9| |7 to 8|R-1.9|R-1.9|R-1.9|

  Notes: 1 Insulation R-values, measured in [°F•h•ft 2 /(Btu•in)] [(m•K)/W], are for the insulation as installed and do not include film resistance. The required minimum thicknesses do not consider water vapor transmission and possible surface condensation. Where portions of the building envelope are used as a plenum enclosure, building envelope insulation shall be as required by the most restrictive condition of Section E 503.4.7.1 or ASHRAE 90.1, depending on whether the plenum is located in the roof, wall, or floor. Insulation resistance measured on a horizontal plane in accordance with ASTM C518 at a mean temperature of 75°F (24°C) at the installed thickness. 2 Includes attics above insulated ceilings, parking garages and crawl spaces. 3 Includes return air plenums, with or without exposed roofs above. 4 Return ducts in this duct location do not require insulation.

  TABLE E 503.7.3(1) MINIMUM PIPE INSULATION THICKNESS FOR HEATING AND HOT WATER SYSTEMS [1, 2, 3, 4, 5]

  (STEAM, STEAM CONDENSATE, HOT WATER HEATING, AND DOMESTIC WATER SYSTEMS)

  [ASHRAE 90.1: TABLE 6.8.3-1]

• § 609.10 High relevance — show source text

  [OSHPD 1, 1R, 2, 3, 4 & 5] Prior to utilization of newly constructed or altered potable water piping systems, all affected potable water piping shall be disinfected using pro- cedures prescribed in California Plumbing Code Sections 609.10(1) through 609.10(5). The method to be followed shall be that prescribed by the Health Authority or, in case no method is prescribed by it, the following: (1) The pipe system shall be flushed with clean, potable water until potable water appears at the points of the outlet. (2) The system or parts thereof shall be filled with a waterchlorine solution containing not less than 50 parts per million of chlorine, and the system or part thereof shall be valved-off and allowed to stand for 24 hours; or, the system or part thereof shall be filled with a water-chlorine solution containing not less than 200 parts per million of chlorine and allowed to stand for 3 hours.

  (3) Following the allowed standing time, the system shall be flushed with clean, potable water until the chlorine residual in the water coming from the system does not exceed the chlorine residual in the flushing water.

  (4) The procedure shall be repeated where it is shown by a bacteriological examination made by an approved agency that contamination persists in the system. (5) [OSHPD 1, 1R, 2, 3, 4 & 5] Disinfection shall be com- pleted no more than three weeks before whole or partial beneficial occupancy.

  (a) Where occupancy is delayed two weeks from disin- fection, flushing of all fixtures shall again be com- pleted.

  (b) Where occupancy is delayed four weeks after disin- fection, disinfection and flushing shall again be com- pleted. 609.11 Water Hammer. [Not adopted by HCD] Building water supply systems where quick-acting valves are installed shall be provided with water hammer arrester(s) to absorb high pressures resulting from the quick closing of these valves. Water hammer arresters shall be approved mechanical devices that comply with ASSE 1010 or PDI-WH 201 and shall be installed as close as possible to quick-acting valves.

  609.11.1 Mechanical Devices. Where listed mechanical devices are used, the manufacturer’s specifications as to location and method of installation shall be followed.

  609.12 Pipe Insulation. Insulation of domestic hot water piping shall be in accordance with Section 609.12.1 and Section 609.12.2.

  609.12.1 Insulation Requirements. Domestic hot water piping shall be insulated. 609.12.2 Pipe Insulation Wall Thickness. Hot water pipe insulation shall have a minimum wall thickness of not less than the diameter of the pipe for a pipe up to 2 inches (50 mm) in diameter. Insulation wall thickness shall be not less than 2 inches (51 mm) for a pipe of 2 inches (50 mm) or more in diameter. Exceptions: (1) Piping that penetrates framing members shall not be required to have pipe insulation for the distance of the framing penetration. (2) Hot water piping between the fixture control valve or supply stop and the fixture or appliance shall not be required to be insulated. 609.12.3 California Energy Code Pipe Insulation _**Requirements.