Title 24 · California Energy Code

What are the requirements for water-heating recirculation loops serving multiple dwelling units, hotels and nonresidential buildings?

If your building has a central hot‑water recirculation loop for apartments, hotels, or nonresidential spaces, the California Energy Code requires specific hardware and piping: an air‑release or vertical pump, a check valve between pump and heater, a hose‑bibb plus isolation for priming, isolation valves on both sides of the pump, no ties to the heater drain port, and a cold‑supply check valve with expansion‑tank compliance — all listed in **§ 110.3(c)4**.

Ask a question free See coverage

Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

The California Energy Code requires that a water‑heating recirculation loop serving multiple dwelling units, high‑rise residential, hotel/motel, and nonresidential occupancies meet specific installation details (air elimination, backflow prevention, pump isolation/priming, and piping connections) identified in § 110.3(c)4. These requirements are mandatory and are summarized in six subitems (A–F) that set the field‑level equipment and piping details to ensure energy‑efficient, serviceable, and safe recirculation systems. § 110.3(c)4 is the controlling provision for these loops.

The single most important rule: install the recirculation loop so air can be removed, flow cannot backfeed the heater, and the pump can be isolated and primed — exactly as required by § 110.3(c)4.

Requirements in detail

Below I break the six required items (A–F) from § 110.3(c)4 into decision‑relevant design checks you will use on drawings and at the jobsite.

Key design / construction checks (table)

Design / requirement Required value or action Code Reference
Air elimination (automatic air release valve or vertical pump) Install an automatic air release valve on the inlet side of the recirculation pump no more than 4 feet from the pump. Valve must be mounted on top of a vertical riser ≥ 12 inches and be accessible for replacement/repair. Alternative: install the pump on a vertical section of the return line. § 110.3(c)4A
Recirculation loop backflow prevention Provide a check valve or similar device between the recirculation pump and the water‑heating equipment to prevent reverse flow. § 110.3(c)4B
Pump priming / hose bibb Provide a hose bibb between the pump and the water‑heating equipment with an isolation valve between the hose bibb and the water‑heating equipment (used to bleed air after pump replacement). § 110.3(c)4C
Pump isolation valves Install isolation valves on both sides of the pump. (These may be integral to the pump flange.) One of these may be the isolation valve required for the hose bibb above. § 110.3(c)4D
Tank connections / drain port prohibition Cold water piping and recirculation loop piping shall not be connected to the hot water storage tank drain port. Storage water heaters/boilers must be plumbed per manufacturer instructions. § 110.3(c)4E
Cold‑water supply backflow prevention & expansion tank Install a check valve on the cold water supply line between the hot water system and the next closest tee on the cold water supply. The system must comply with expansion‑tank requirements described in the California Plumbing Code § 608.3 (as referenced by the Energy Code). § 110.3(c)4F; see also § L501.5 / § L501.8 (CPC recirculation control & air elimination)

Notes on the table:

  • The bolded numeric thresholds — 4 feet and 12 inches — are explicit in the code text and are critical field checks.
  • The code defines a recirculation loop in the same subsection: it is the supply portion tied to multiple branches and a return completing the loop back to the water‑heating equipment; that definition is part of § 110.3(c)4.

Short elaboration on each item

  • Air elimination: the code requires either an automatic air release valve placed very near the pump (inlet side and ≤ 4 ft) mounted on a vertical riser at least 12 in. tall, or the pump located on a vertical return. This prevents air locks and keeps the valve serviceable. § 110.3(c)4A
  • Backflow prevention: a check valve between pump and heater prevents the recirculation loop from “backfeeding” into the heater or other distribution piping. § 110.3(c)4B
  • Pump priming & hose bibb: the required hose bibb and an isolation valve allow bleeding/priming after maintenance or pump replacement. § 110.3(c)4C–D
  • Prohibition on using the tank drain port: the cold supply and recirculation piping must not tie into the water‑heater drain port (this port must remain available for proper draining). § 110.3(c)4E
  • Cold water supply check valve and expansion tank: a check valve is required on the cold supply between the hot water system and the next tee; expansion‑tank requirements follow the California Plumbing Code and are explicitly cross‑referenced. § 110.3(c)4F

Exceptions & special cases

  • 110.3(c)4 applies to multiple dwelling units, high‑rise residential, hotel/motel and nonresidential occupancies. Recirculation rules for individual dwelling units are handled differently — individual‑unit recirculation is limited to demand systems with manual on/off control per the Residential Reference Appendix (see Sections on multifamily/domestic hot water requirements). For example, Section 170.2(d)1 addresses individual systems and allowable demand recirculation controls. When designing, confirm whether the system is a central system (subject to § 110.3(c)4) or an individual/compact system (different rules).
  • The code allows the alternative of installing the pump on a vertical section of return piping instead of adding the air‑release valve (this is explicitly allowed in § 110.3(c)4A).
  • The Energy Code cross‑references Plumbing Code requirements (e.g., expansion tank) rather than restating them; consult the California Plumbing Code (Appendix L and other relevant L sections) for pump controls, system balancing, and air‑elimination details when needed.

Common mistakes

  • Placing the air‑release valve on the discharge side of the pump or more than 4 feet from the pump instead of on the inlet side ≤ 4 ft. Check § 110.3(c)4A.
  • Omitting the check valve between the recirculation pump and the heater (risking reverse flow). Check § 110.3(c)4B.
  • Connecting the recirculation loop or cold supply to the water‑heater drain port (the code prohibits this). Check § 110.3(c)4E.
  • Forgetting isolation valves on both sides of the pump or failing to provide the hose bibb/isolation arrangement required for priming/bleeding. Check § 110.3(c)4C–D.
  • Not providing the cold‑water check valve between the system and the next tee (or ignoring expansion tank requirements referenced to the Plumbing Code). Check § 110.3(c)4F and CPC § 608.3.

Worked example — concrete scenario with numbers

Scenario: central hot‑water recirculation loop serving a 50‑unit apartment building. The mechanical contractor proposes a horizontal return run with a recirculation pump mounted on a short vertical stub.

Checklist (apply § 110.3(c)4 to verify compliance):

  1. Air release: the contract installer will mount an automatic air release valve on the inlet side of the pump, within 3 ft of the pump (meets the ≤ 4 ft requirement), and the valve is mounted on a vertical riser that is 14 in. tall (meets the ≥ 12 in. requirement). This satisfies § 110.3(c)4A.
  2. Backflow prevention: a spring check valve will be installed in the piping between the pump discharge and the primary water‑heater inlet piping so water cannot flow backward — satisfies § 110.3(c)4B.
  3. Priming / hose bibb: provide a hose bibb on the pipe between pump and heater; include an isolation valve between that hose bibb and the heater (this is used to bleed air when servicing the pump) — satisfies § 110.3(c)4C.
  4. Isolation valves: two gate or ball valves (one on each side of the pump) are installed; the downstream isolation is the same valve used for the hose bibb isolation — satisfies § 110.3(c)4D.
  5. Tank drain port: confirm neither the cold supply nor the recirculation return is tied into the hot‑water storage tank drain port; plumber demonstrates separate connections per manufacturer instructions — satisfies § 110.3(c)4E.
  6. Cold water check valve & expansion tank: install a check valve on cold supply between the hot water system and the next tee; confirm system expansion control complies with the Plumbing Code (expansion tank per CPC § 608.3). Satisfies § 110.3(c)4F and referenced CPC requirements.

If each item above is met and inspected, the installation conforms to the configuration requirements of § 110.3(c)4.

Related provisions

  • § 110.3(c)4 — Water heating recirculation loop requirements (controlling section discussed here).
  • § 160.4(a) — Mandatory statement that water‑heating recirculation loops serving multiple dwelling units must meet § 110.3(c)4.
  • § 110.3(c)2 — Controls for hot water distribution systems (requires circulating pumps or heat‑trace systems to be capable of automatically turning off). Relevant to pump control strategies.
  • § 170.2(d) (and § 170.2(d)1–2) — Multifamily and hotel/motel water‑heating system requirements (when central systems and mixing/master valves are required). Use these sections to determine system type and additional requirements for central distribution.
  • California Plumbing Code, Appendix L (L 501.4, L 501.6, L 501.8, etc.) — Recirculation pump controls, balancing, and air elimination (CPC provides detailed requirements for controls and system balancing that the Energy Code references).

Code references

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

  • § 110.3 High relevance — show source text
    1. Outlet temperature controls. On systems that have a total capacity greater than 167,000 Btu/hr, outlets that require higher than service water temperatures as listed in the ASHRAE Handbook, Applications Volume, shall have separate remote heaters, heat exchangers or boosters to supply the outlet with the higher temperature. Exception to Section 110.3(c)1: Systems covered by California Plumbing Code Section 613.0 shall instead follow the requirements of that section.
    2. Controls for hot water distribution systems. Service hot water systems with circulating pumps or with electrical heat trace systems shall be capable of automatically turning off the system. Exception to Section 110.3(c)2: Systems serving healthcare facilities.
    3. Insulation. Unfired service water heater storage tanks and backup tanks for solar water-heating systems shall have: A. External insulation with an installed R -value of at least R-3.5; or

    B. Internal and external insulation with a combined R -value of at least R-16; or

    C. The heat loss of the tank surface based on an 80°F water-air temperature difference shall be less than 6.5 Btu per hour per square foot. 4. Water heating recirculation loops serving multiple dwelling units, high-rise residential, hotel/motel, and nonresiden- tial occupancies. A water heating recirculation loop is a type of hot water distribution system that reduces the time needed to deliver hot water to fixtures that are distant from the water heater, boiler or other water heating equipment. The recirculation loop is comprised of a supply portion, connected to branches that serve multiple dwelling units, guest rooms, or fixtures and a return portion that completes the loop back to the water heating equipment. A water heating recirculation loop shall meet the following requirements: A. Air release valve or vertical pump installation. An automatic air release valve shall be installed on the recirculation loop piping on the inlet side of the recirculation pump and no more than 4 feet from the pump. This valve shall be mounted on top of a vertical riser at least 12 inches in length and shall be accessible for replacement and repair. Alternatively, the pump shall be installed on a vertical section of the return line. B. Recirculation loop backflow prevention. A check valve or similar device shall be located between the recirculation pump and the water heating equipment to prevent water from flowing backwards though the recirculation loop. C. Equipment for pump priming. A hose bibb shall be installed between the pump and the water heating equipment. An isolation valve shall be installed between the hose bibb and the water heating equipment. This hose bibb is used for bleeding air out of the pump after pump replacement. D. Pump isolation valves. Isolation valves shall be installed on both sides of the pump. These valves may be part of the flange that attaches the pump to the pipe. One of the isolation valves may be the same isolation valve as in Item C. E. Cold water supply and recirculation loop connection to hot water storage tank. Storage water heaters and boilers shall be plumbed in accordance with the manufacturer’s specifications The cold water piping and the recirculation loop piping shall not be connected to the hot water storage tank drain port. F. Cold water supply backflow prevention. A check valve shall be installed on the cold water supply line between the hot water system and the next closest tee on the cold water supply line.

  • § 170.1 High relevance — show source text
    1. Central systems. For systems serving multiple dwelling units, the water-heating system shall meet the applicable requirement of A through F, or shall meet the performance compliance requirements of Section 170.1: A. For heat pump water-heating systems serving multiple dwelling units, the water-heating system shall be installed according to the manufacturer’s design and installation guidelines and meet the following requirements, or meet the requirements of NEEA Advanced Water Heater Specification for commercial heat pump water heater Tier 2 or higher: i. The primary heat pump water heater shall be a single-pass heat pump water heater. ii. The hot water return from the recirculation loop shall connect to a recirculation loop tank and shall not directly connect to the primary heat pump water heater inlet or the primary thermal storage tanks. iii. The fuel source for the recirculation loop tank shall be electricity. iv. The primary storage tank temperature setpoint shall be at least 135°F. v. The recirculation loop tank temperature setpoint shall be at least 10°F lower than the primary thermal storage tank temperature setpoint. vi. The minimum heat pump water heater compressor cut-off temperature shall be equal to or lower than 40°F ambient air temperature. vii. Design documentation shall be provided in accordance with JA14.4. B. For gas or propane systems serving multiple dwelling units, the water-heating system that includes the following components shall be installed: i. For Climate Zones 1 through 9, gas service water-heating systems with a total installed gas water-heating input capacity of 1 MMBtu/h or greater shall have gas service water-heating equipment with a minimum thermal efficiency of 90 percent. Multiple units are allowed to meet this requirement with an input capacity-weighted average of at least 90 percent. Exception 1 to Section 170.2(d)Bi: Individual gas water heaters with input capacity at or below 100,000 Btu/h shall not be included in the calculations of the total system input or total system efficiency. Exception 2 to Section 170.2(d)Bi: If 25 percent of the annual water-heating requirement is provided by sitesolar energy or site-recovered energy. ii. A solar water-heating system meeting the installation criteria specified in Reference Residential Appendix RA4 and with a minimum solar savings fraction of either a. or b. below: a. A minimum solar savings fraction of 0.20 in Climate Zones 1 through 9 or a minimum solar savings fraction of 0.35 in Climate Zones 10 through 16; or b. A minimum solar savings fraction of 0.15 in Climate Zones 1 through 9 or a minimum solar savings fraction of 0.30 in Climate Zones 10 through 16. In addition, a drain water heat recovery system that is field verified as specified in the Reference Appendix RA3.6.9. C. All hot water piping shall be sized in accordance with the California Plumbing Code Appendix M. D. The central system shall have a recirculation system with a mechanical or digital thermostatic master mixing valve on each distribution supply and return loop, and meet the requirements specified in the Residential Reference Appendix RA4.4.19.

    Exception to Section 170.2(d)2D : Buildings with eight or fewer dwelling units. E. Insulation for hot water pipes and plumbing appurtenances shall be field verified as specified in Residential Reference Appendix RA3.6.3. F. A water-heating system serving multiple dwelling units determined by the Executive Director to use no more energy than the one specified in Subsection A or B above.

    2025 CALIFORNIA ENERGY CODE 257

  • § 170.1. High relevance — show source text

    MULTIFAMILY BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES

    (d) Domestic hot water systems. Water-heating systems shall meet the applicable requirements of 1 or 2 below:

    1. Individual systems. For systems serving individual dwelling units, the water-heating system shall meet the requirement of either A or B, or shall meet the performance compliance requirements of Section 170.1. For recirculation distribution systems serving individual dwelling units, only demand recirculation systems with manual on/off control as specified in the Reference Appendix RA4.4.9 shall be used. A. A single 240 volt heat pump water heater. In addition, meet the following: i. A compact hot water distribution system as specified in Reference Appendix RA4.4.6 in Climate Zones 1 and 16; and

    ii. A drain water heat recovery system that is field verified as specified in the Reference Appendix RA3.6.9 in Climate Zone 16.

    B. A single heat pump water heater that meets the requirements of NEEA Advanced Water Heater Specification Tier 3 or higher. In addition, for Climate Zone 16, a drain water heat recovery system that is field verified as specified in Reference Appendix RA3.6.9. Exception 1 to Section 170.2(d)1: Multifamily buildings four habitable stories or greater may install a gas or propane instantaneous water heater with an input of 200,000 Btu per hour or less and no storage tank. Exception 2 to Section 170.2(d)1: A 120V HPWH may be installed in place of a 240V HPWH for new dwelling units with one bedroom or less.

    1. Central systems. For systems serving multiple dwelling units, the water-heating system shall meet the applicable requirement of A through F, or shall meet the performance compliance requirements of Section 170.1: A. For heat pump water-heating systems serving multiple dwelling units, the water-heating system shall be installed according to the manufacturer’s design and installation guidelines and meet the following requirements, or meet the requirements of NEEA Advanced Water Heater Specification for commercial heat pump water heater Tier 2 or higher: i. The primary heat pump water heater shall be a single-pass heat pump water heater. ii. The hot water return from the recirculation loop shall connect to a recirculation loop tank and shall not directly connect to the primary heat pump water heater inlet or the primary thermal storage tanks. iii. The fuel source for the recirculation loop tank shall be electricity. iv. The primary storage tank temperature setpoint shall be at least 135°F. v. The recirculation loop tank temperature setpoint shall be at least 10°F lower than the primary thermal storage tank temperature setpoint. vi. The minimum heat pump water heater compressor cut-off temperature shall be equal to or lower than 40°F ambient air temperature. vii. Design documentation shall be provided in accordance with JA14.4. B. For gas or propane systems serving multiple dwelling units, the water-heating system that includes the following components shall be installed: i. For Climate Zones 1 through 9, gas service water-heating systems with a total installed gas water-heating input capacity of 1 MMBtu/h or greater shall have gas service water-heating equipment with a minimum thermal efficiency of 90 percent. Multiple units are allowed to meet this requirement with an input capacity-weighted average of at least 90 percent.
  • § 25218.5 High relevance — show source text

    These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|

    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 160.4—MANDATORY REQUIREMENTS FOR WATER-HEATING SYSTEMS

    (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

    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.
  • § 170.1. High relevance — show source text

    000|≥10,000|≥5,000|≥5,000|≥2,000|≥2,000|≥2,000|≥2,000|≥2,000| |≥60% and <70%|≥2,000|≥2,000|≥6,000|≥6,000|≥6,000|NR|NR|≥18,000|≥9,000|≥4,000|≥4,000|≥2,000|≥2,000|≥2,000|≥2,000|≥2,000| |≥70% and <80%|≥2,000|≥2,000|≥6,000|≥5,000|≥5,000|NR|NR|≥15,000|≥8,000|≥3,000|≥3,000|≥2,000|≥2,000|≥2,000|≥2,000|≥2,000| |≥80%|≥2,000|≥2,000|≥6,000|≥5,000|≥5,000|NR|NR|≥12,000|≥7,000|≥3,000|≥3,000|≥2,000|≥2,000|≥2,000|≥2,000|≥2,000|

    256 2025 CALIFORNIA ENERGY CODE

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

    MULTIFAMILY BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES

    (d) Domestic hot water systems. Water-heating systems shall meet the applicable requirements of 1 or 2 below:

    1. Individual systems. For systems serving individual dwelling units, the water-heating system shall meet the requirement of either A or B, or shall meet the performance compliance requirements of Section 170.1. For recirculation distribution systems serving individual dwelling units, only demand recirculation systems with manual on/off control as specified in the Reference Appendix RA4.4.9 shall be used. A. A single 240 volt heat pump water heater. In addition, meet the following: i. A compact hot water distribution system as specified in Reference Appendix RA4.4.6 in Climate Zones 1 and 16; and

    ii. A drain water heat recovery system that is field verified as specified in the Reference Appendix RA3.6.9 in Climate Zone 16.

    B. A single heat pump water heater that meets the requirements of NEEA Advanced Water Heater Specification Tier 3 or higher. In addition, for Climate Zone 16, a drain water heat recovery system that is field verified as specified in Reference Appendix RA3.6.9. Exception 1 to Section 170.2(d)1: Multifamily buildings four habitable stories or greater may install a gas or propane instantaneous water heater with an input of 200,000 Btu per hour or less and no storage tank. Exception 2 to Section 170.2(d)1: A 120V HPWH may be installed in place of a 240V HPWH for new dwelling units with one bedroom or less.

    1. **Central systems.
  • § 608.3. High relevance — show source text

    A water heating recirculation loop shall meet the following requirements: A. Air release valve or vertical pump installation. An automatic air release valve shall be installed on the recirculation loop piping on the inlet side of the recirculation pump and no more than 4 feet from the pump. This valve shall be mounted on top of a vertical riser at least 12 inches in length and shall be accessible for replacement and repair. Alternatively, the pump shall be installed on a vertical section of the return line. B. Recirculation loop backflow prevention. A check valve or similar device shall be located between the recirculation pump and the water heating equipment to prevent water from flowing backwards though the recirculation loop. C. Equipment for pump priming. A hose bibb shall be installed between the pump and the water heating equipment. An isolation valve shall be installed between the hose bibb and the water heating equipment. This hose bibb is used for bleeding air out of the pump after pump replacement. D. Pump isolation valves. Isolation valves shall be installed on both sides of the pump. These valves may be part of the flange that attaches the pump to the pipe. One of the isolation valves may be the same isolation valve as in Item C. E. Cold water supply and recirculation loop connection to hot water storage tank. Storage water heaters and boilers shall be plumbed in accordance with the manufacturer’s specifications The cold water piping and the recirculation loop piping shall not be connected to the hot water storage tank drain port. F. Cold water supply backflow prevention. A check valve shall be installed on the cold water supply line between the hot water system and the next closest tee on the cold water supply line. The system shall comply with the expansion tank requirements as described in the California Plumbing Code Section 608.3.

    52 2025 CALIFORNIA ENERGY CODE

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

    ALL OCCUPANCIES—MANDATORY REQUIREMENTS FOR THE MANUFACTURE, CONSTRUCTION AND INSTALLATION OF SYSTEMS, EQUIPMENT AND BUILDING COMPONENTS

    1. Service water heaters in state buildings. Any newly constructed building constructed by the State shall derive its service water heating from a system that provides at least 60 percent of the energy needed for service water heating from site solar energy or recovered energy, per the statutory requirement of California Public Resources Code Section 25498.

    Exception to Section 110.3(c)5: Buildings for which the state architect determines that service water heating from site solar energy or recovered energy is economically or physically infeasible. 6. Isolation valves. Instantaneous water heaters with an input rating greater than 6.8 kBTU/hr (2 kW) shall have isolation valves on both the cold water supply and the hot water pipe leaving the water heater, and hose bibbs or other fittings on each valve for flushing the water heater when the valves are closed. 7. Air-source heat pump water heaters (HPWH). HPWH shall meet the following requirements: A. Backup heat. Backup heat is required for systems where inlet air is unconditioned, unless the compressor cut-off temperature is below the Heating Winter Median of Extremes for the closest location listed in Table 2-3 from Reference Joint Appendix JA2. Backup heat may be internal or external to the HPWH. B. Ventilation. Consumer integrated HPWHs shall meet one of the ventilation requirements below.

  • § 110.3 High relevance — show source text

    SECTION 110.3—MANDATORY REQUIREMENTS FOR SERVICE WATER-HEATING SYSTEMS AND EQUIPMENT

    (a) Certification by manufacturers. Any service water- heating system or equipment may be installed only if the manufacturer has certified that the system or equipment complies with all of the requirements of this subsection for that system or equipment.

    1. Temperature controls for service water-heating systems. Service water-heating systems shall be equipped with automatic temperature controls capable of adjustment from the lowest to the highest acceptable temperature settings for the intended use as listed in Table 3, Chapter 50 of the ASHRAE Handbook, HVAC Applications Volume or Table 613.1 of the Cali- fornia Plumbing Code for healthcare facilities. Exception to Section 110.3(a)1: Residential occupancies.

    (b) Efficiency. Equipment shall meet the applicable requirements of the Appliance Efficiency Regulations as required by Section 110.1, subject to the following:

    1. If more than one standard is listed in the Appliance Efficiency Regulations, the equipment shall meet all the standards listed; and

    2. If more than one test method is listed in the Appliance Efficiency Regulations, the equipment shall comply with the applicable standard when tested with each test method; and

    3. Where equipment can serve more than one function, such as both heating and cooling, or both space heating and water heating, it shall comply with all the requirements applicable to each function; and

    4. Where a requirement is for equipment rated at its “maximum rated capacity” or “minimum rated capacity,” the capacity shall be as provided for and allowed by the controls, during steady-state operation.

    (c) Installation. Any service water-heating system or equipment may be installed only if the system or equipment complies with all of the applicable requirements of this subsection for the system or equipment.

    1. Outlet temperature controls. On systems that have a total capacity greater than 167,000 Btu/hr, outlets that require higher than service water temperatures as listed in the ASHRAE Handbook, Applications Volume, shall have separate remote heaters, heat exchangers or boosters to supply the outlet with the higher temperature. Exception to Section 110.3(c)1: Systems covered by California Plumbing Code Section 613.0 shall instead follow the requirements of that section.
    2. Controls for hot water distribution systems. Service hot water systems with circulating pumps or with electrical heat trace systems shall be capable of automatically turning off the system. Exception to Section 110.3(c)2: Systems serving healthcare facilities.
    3. Insulation. Unfired service water heater storage tanks and backup tanks for solar water-heating systems shall have: A. External insulation with an installed R -value of at least R-3.5; or

    B. Internal and external insulation with a combined R -value of at least R-16; or

    C. The heat loss of the tank surface based on an 80°F water-air temperature difference shall be less than 6.5 Btu per hour per square foot. 4. Water heating recirculation loops serving multiple dwelling units, high-rise residential, hotel/motel, and nonresiden- tial occupancies. A water heating recirculation loop is a type of hot water distribution system that reduces the time needed to deliver hot water to fixtures that are distant from the water heater, boiler or other water heating equipment. The recirculation loop is comprised of a supply portion, connected to branches that serve multiple dwelling units, guest rooms, or fixtures and a return portion that completes the loop back to the water heating equipment.

  • § 180.2 High relevance — show source text

    Existing duct systems constructed, insulated or sealed with asbestos are not required to comply with the requirements of Subsection 180.2(b)2Biiib.

    2025 CALIFORNIA ENERGY CODE 279

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

    MULTIFAMILY BUILDINGS—ADDITIONS, ALTERATIONS AND REPAIRS TO EXISTING MULTIFAMILY BUILDINGS

    1. Hot water systems . Altered or replacement water-heating systems or components serving individual dwelling units shall meet the applicable requirements below: A. Pipe insulation. For newly installed piping and existing accessible piping, the insulation requirements of Section 160.4(e) shall be met. B. Distribution system. For recirculation distribution system serving individual dwelling units, only demand recirculation systems with manual on/off control as specified in Reference Appendix RA4.4.9 shall be installed. C. Water-heating system. The water-heating system shall meet one of the following: i. A natural gas or propane water-heating system; or ii. A single heat pump water heater. The storage tank shall not be located outdoors and shall be placed on an incompressible, rigid insulated surface with a minimum thermal resistance of R-10. The water heater shall be installed with a communication interface that either meets the requirements of Section 110.12(a) or has an ANSI/CTA-2045-B communication port; or iii. A single heat pump water heater that meets the requirements of NEEA Advanced Water Heater Specification Tier 3 or higher; or iv. If the existing water heater is an electric resistance water heater, a consumer electric water heater. v. A water-heating system determined by the Executive Director to use no more energy than the one specified in Sections 180.2(b)3Ci through iii above; or if no natural gas is connected to the existing water heater location, a water-heating system determined by the Executive Director to use no more energy than the one specified in Section 180.2(b)3Civ above.

    2. Lighting. A. Dwelling unit lighting. The altered lighting system shall meet the lighting requirements of Section 160.5(a). The altered luminaires shall meet the luminaire efficacy requirements of Section 160.5(a). Where existing screw base sockets are present in ceiling-recessed luminaires, removal of these sockets is not required, provided that new JA8 compliant trim kits or lamps designed for use with recessed downlights or luminaires are installed. B. Common use area—lighting, sign lighting, and electrical power distribution systems . i. Spaces with lighting systems installed for the first time shall meet the applicable requirements of Sections 110.9, 160.5(b)1, 160.5(b)2, 160.5(b)3, 160.5(b)4, 160.5(c), 160.5(e), 170.2(b), and 170.2(e)1 through 170.2(e)6. ii. When the requirements of Section 160.5(b)4D are triggered by the addition of skylights to an existing building and the lighting system is not recircuited, the daylighting control need not meet the multi-level requirements in Section 160.5(b)4D. iii. New internally and externally illuminated signs shall meet the requirements of Sections 110.9, 160.5(d) and 170.2(e)7. iv. Altered indoor lighting systems.

  • § 1.5 High relevance — show source text

    5**|1.5 to < 4|4 to < 8|8 and
    larger| |Space heating (Steam, Steam Condensate, Refrigerant, Space Heating)|Space heating (Steam, Steam Condensate, Refrigerant, Space Heating)|Space heating (Steam, Steam Condensate, Refrigerant, Space Heating)|Space heating (Steam, Steam Condensate, Refrigerant, Space Heating)|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)| |Below 40|0.20–0.26|50|Inches|1.0|1.5|1.5|1.5|1.5| |Below 40|0.20–0.26|50|_R-_value|R-8.5|R-14|R-12|R-10|R-9| |1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|1. These thicknesses are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or
    additional insulation.|

    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 160.4—MANDATORY REQUIREMENTS FOR WATER-HEATING SYSTEMS

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

  • § 110.12 High relevance — show source text

    iii. Altered space-conditioning systems. When a space-conditioning system is altered by the installation or replacement of space-conditioning system equipment (including replacement of the air handler, outdoor condensing unit of a split system air conditioner or heat pump, or cooling or heating coil: a. For all altered units where the existing thermostat does not comply with the requirements for demand responsive controls specified in Section 110.12, the existing thermostat shall be replaced with a demand responsive thermostat that complies with Section 110.12. All newly installed space-conditioning systems requiring a thermostat shall be equipped with a demand responsive thermostat that complies with Section 110.12; and

    b. The duct system that is connected to the new or replaced space-conditioning system equipment shall be sealed, if the duct system meets the criteria of Section 120.4(g), as confirmed through acceptance testing, in accordance with the applicable procedures for duct sealing of altered existing duct systems as specified in Reference Nonresidential Appendix NA7.5.3, and conforming to the applicable leakage compliance criteria in Section 180.2(b)2Bii. Exception 1 to Section 180.2(b)2Biiib: duct sealing . Buildings altered so that the duct system no longer meets the criteria of Section 170.2(c)4Ji are not required to comply with Subsection 180.2(b)2Biiib. Exception 2 to Section 180.2(b)2Biiib: duct sealing . Duct systems that are documented to have been previously sealed as confirmed through acceptance testing in accordance with procedures in the Reference Nonresidential Appendix NA7.5.3 are not required to comply with Subsection 180.2(b)2Biiib. Exception 3 to Section 180.2(b)2Biiib: duct sealing . Existing duct systems constructed, insulated or sealed with asbestos are not required to comply with the requirements of Subsection 180.2(b)2Biiib.

    2025 CALIFORNIA ENERGY CODE 279

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

    MULTIFAMILY BUILDINGS—ADDITIONS, ALTERATIONS AND REPAIRS TO EXISTING MULTIFAMILY BUILDINGS

    1. Hot water systems . Altered or replacement water-heating systems or components serving individual dwelling units shall meet the applicable requirements below: A. Pipe insulation. For newly installed piping and existing accessible piping, the insulation requirements of Section 160.4(e) shall be met. B. Distribution system. For recirculation distribution system serving individual dwelling units, only demand recirculation systems with manual on/off control as specified in Reference Appendix RA4.4.9 shall be installed. C. Water-heating system. The water-heating system shall meet one of the following: i. A natural gas or propane water-heating system; or ii. A single heat pump water heater. The storage tank shall not be located outdoors and shall be placed on an incompressible, rigid insulated surface with a minimum thermal resistance of R-10. The water heater shall be installed with a communication interface that either meets the requirements of Section 110.12(a) or has an ANSI/CTA-2045-B communication port; or iii. A single heat pump water heater that meets the requirements of NEEA Advanced Water Heater Specification Tier 3 or higher; or iv. If the existing water heater is an electric resistance water heater, a consumer electric water heater.
  • § 140.4 High relevance — show source text

    30 percent of the peak heat rejection of the cooling system; or B. 30 percent of SWHCAP.

    Exception to Section 140.4(s): Buildings with a computer room heat recovery system or wastewater heat recovery system capable of providing not less than 25 percent of SWHCAP + HCAP.

    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, 25402.8, and 25943, Public Resources Code .

    SECTION 140.5—PRESCRIPTIVE REQUIREMENTS FOR SERVICE WATER-HEATING SYSTEMS

    (a) Nonresidential occupancies. Service water-heating systems in nonresidential buildings shall meet the requirements of 1 or 2 below, or meet the performance compliance requirements of Section 140.1:

    1. School buildings less than 25,000 square feet and less than 4 stories in Climate Zones 2 through 15. A heat pump water-heating system that meets the applicable requirements of Sections 110.1, 110.3 and 120.3.

    Exception to Section 140.5(a)1: A water-heating system serving an individual bathroom space may be an instantaneous electric water heater.

    1. All other occupancies. A service water-heating system that meets the applicable requirements of Sections 110.1, 110.3, 120.3 and 140.5(c).

    (b) Hotel/motel occupancies. A service water-heating system installed in hotel/motel buildings shall meet the requirements of Section 170.2(d).

    (c) High-capacity service water-heating systems . Gas service water-heating systems with a total installed gas water-heating input capacity of 1 MMBtu/h or greater shall have gas service water-heating equipment with a minimum thermal efficiency of 90 percent. Multiple units can meet this requirement if the water-heating input provided by equipment with thermal efficiencies above and below 90 percent averages out to an input capacity-weighted average of at least 90 percent.

    Exception 1 to Section 140.5(c): If 25 percent of the annual service water-heating requirement is provided by site-solar energy or site-recovered energy.

    Exception 2 to Section 140.5(c): Water heaters installed in individual dwelling units.

    Exception 3 to Section 140.5(c): Individual gas water heaters with input capacity at or below 100,000 Btu/h shall not be included in the calculations of the total system input or total system efficiency.

    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, 25402.8, and 25943, Public Resources Code.

    2025 CALIFORNIA ENERGY CODE 129

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

    NONRESIDENTIAL AND HOTEL/MOTEL OCCUPANCIES—PERFORMANCE AND PRESCRIPTIVE

    COMPLIANCE APPROACHES FOR ACHIEVING ENERGY EFFICIENCY

    SECTION 140.6—PRESCRIPTIVE REQUIREMENTS FOR INDOOR LIGHTING

  • § 170.2 High relevance — show source text

    Exception 2 to Section 170.2(d)Bi: If 25 percent of the annual water-heating requirement is provided by sitesolar energy or site-recovered energy. ii. A solar water-heating system meeting the installation criteria specified in Reference Residential Appendix RA4 and with a minimum solar savings fraction of either a. or b. below: a. A minimum solar savings fraction of 0.20 in Climate Zones 1 through 9 or a minimum solar savings fraction of 0.35 in Climate Zones 10 through 16; or b. A minimum solar savings fraction of 0.15 in Climate Zones 1 through 9 or a minimum solar savings fraction of 0.30 in Climate Zones 10 through 16. In addition, a drain water heat recovery system that is field verified as specified in the Reference Appendix RA3.6.9. C. All hot water piping shall be sized in accordance with the California Plumbing Code Appendix M. D. The central system shall have a recirculation system with a mechanical or digital thermostatic master mixing valve on each distribution supply and return loop, and meet the requirements specified in the Residential Reference Appendix RA4.4.19.

    Exception to Section 170.2(d)2D : Buildings with eight or fewer dwelling units. E. Insulation for hot water pipes and plumbing appurtenances shall be field verified as specified in Residential Reference Appendix RA3.6.3. F. A water-heating system serving multiple dwelling units determined by the Executive Director to use no more energy than the one specified in Subsection A or B above.

    2025 CALIFORNIA ENERGY CODE 257

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

    MULTIFAMILY BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES

    TABLE 170.2-K—MECHANICAL COMPONENT PACKAGE – MULTIFAMILY STANDARD BUILDING DESIGN Col2 Col3 Col4 Col5 Col6 Col7 Col8 Col9 Col10 Col11 Col12 Col13 Col14 Col15 Col16 Col17
    COMPONENT CZ 1 CZ 2 CZ 3 CZ 4 CZ 5 CZ 6 CZ 7 CZ 8 CZ 9 CZ 10 ** CZ 11** ** CZ 12** ** CZ 13** ** CZ 14** ** CZ 15** ** CZ 16**
    Unitary4 – Balanced Ventilation
    System1HRV/ERV Sensible Recovery
    Efficiency    		 0.67 0.67 NR 0.67 NR NR NR NR NR NR 0.67 0.67 0.67 0.67 NR 0.67
    Unitary4 – Balanced Ventilation
    System1HRV/ERV Fan Efficacy
    (W/cfm)    		 0.6 0.6 1.0 0.6 1.0 1.0 1.0 1.0 1.0 1.0 0.6 0.6 0.6 0.6 1.0 0.

Frequently asked questions

Who must follow § 110.3(c)4?

Any recirculation loop serving multiple dwelling units, high‑rise residential, hotel/motel, or nonresidential occupancies must meet § 110.3(c)4. Single‑unit or certain low‑rise residential recirculation has different, more limited rules—see the multifamily and residential sections.

Is a vertical pump always required?

No. The code allows either an automatic air release valve installed on the inlet side of the pump within 4 ft and on a ≥12 in. vertical riser, or the pump may be installed on a vertical section of the return line as an alternative. § 110.3(c)4A.

Can the pump isolation valves be part of the pump flange?

Yes. Isolation valves may be part of the pump flange that attaches the pump to the pipe; however, you must still have valves on both sides of the pump (one may serve the hose‑bibb isolation). § 110.3(c)4D–C.

May I connect the recirculation loop to the heater drain port to simplify piping?

No. § 110.3(c)4E explicitly prohibits connecting the cold water piping and recirculation loop piping to the hot water storage tank drain port.

Where do I find the expansion‑tank rules referenced by § 110.3(c)4F?

The Energy Code references the California Plumbing Code for expansion‑tank requirements (see CPC § 608.3 and relevant Appendix L rules for recirculation controls and air elimination). Check the CPC for sizing and installation details.

More in California Energy Code

Ask about the California Energy Code

Get cited, plain-English answers on the California Energy Code for your project — any code section, any scenario.

Start Free Trial

Related in the California Energy Code

Are circulating pumps and electrical heat trace required to be capable of automatic shutoff?

How must recirculation pumps and on‑demand systems be controlled and limited?

Hot-water distribution, recirculation and demand controls

California Energy Code