CHBC · California Historical Building Code
Appliance safety and water‑heater temperature/pressure relief
If your project is under the California Historical Building Code, the rule is simple: install appliances so they create no safety hazard (**§ 8‑902.9.1**) and fit storage water heaters with a temperature‑and‑pressure relief valve (**§ 8‑902.9.2**). The CHBC defers technical details (valve type, discharge piping, pressure limits, expansion tanks, etc.) to the California Plumbing Code — so use a listed combination T&P valve, route full‑size, unobstructed discharge piping to an outside/visible termination (6 in–2 ft above grade), ensure valve setting is above supply pressure and ≤ 150 psi, and provide thermal‑expansion control where required. Consult the AHJ early for any historic‑fabric constraints and for approval of equivalent solutions .
Last reviewed: July 6, 2026
What the code requires — plain English
- The California Historical Building Code requires that appliances and equipment (including water heaters) be installed so they create no safety hazard (§ 8-902.9.1) and that storage‑type water heaters be equipped with a temperature‑and‑pressure relief valve installed in accordance with the regular plumbing code (§ 8-902.9.2) .
- In practice that means follow the CHBC requirement to avoid hazards and follow the California Plumbing Code rules for T&P valves, discharge piping, overpressure settings and related devices referenced by the CHBC .
The single most important rule: storage water heaters in CHBC buildings must have a working temperature‑and‑pressure (T&P) relief device and discharge piping installed so they cannot be isolated, will not cause injury or damage, and are terminated where visible — the CHBC requires the device and defers the technical details to the regular plumbing code (§ 8‑902.9.2) .
Requirements in detail
1) CHBC requirement (overall)
- The CHBC states: appliances and equipment (including warm air furnaces, space heaters, ... and water heaters) shall be installed so no safety hazard is created (§ 8‑902.9.1) .
- For storage‑type water heaters, CHBC requires a temperature‑and‑pressure‑relief valve per the regular code (§ 8‑902.9.2) — the CHBC points you to the California Plumbing Code for the technical specifics .
2) Required device and location (from the regular code the CHBC references)
The California Plumbing Code (referenced by the CHBC) provides the technical requirements that implement § 8‑902.9.2, including device type, installation location, and interactions with other system devices:
- Device: an approved, listed combination temperature‑and‑pressure‑relief valve for storage water heaters (combination T&P valve) is required; instantaneous nonstorage heaters under specified size may be excepted .
- No shutoff or isolation: no shutoff valve shall be installed between the relief valve and the water heater, and discharge piping must have no valves, obstructions, or means of isolation .
- Set pressure limit: pressure relief valves must be set at a pressure not more than 150 psi (and must be greater than the building water service pressure) .
- Discharge piping: must be at least the size of the valve outlet, discharge full‑size, be installed to drain by gravity through an air gap to an approved location or outside, and terminate not more than 2 feet (610 mm) and not less than 6 inches (152 mm) above the ground or flood level, pointing downward; the termination must be readily visible and not threaded .
- Drain pans: where a water heater is located in an attic or other sensitive location a watertight pan and drain may be required; discharge from a relief valve into a water heater pan is prohibited .
- Thermal expansion: if the system contains a check valve/backflow preventer (or otherwise traps system pressure), an approved expansion tank or other approved device sized for thermal expansion is required; alternatively an approved relief device may be allowed where listed and limited to a maximum setting (see code) .
Quick reference table (decision‑relevant values)
| Item | Requirement / Value | Code Reference |
|---|---|---|
| Required device for storage water heater | Combination temperature‑and‑pressure‑relief valve | § 8‑902.9.2 (CHBC); CPC § 608.3/505.2 |
| Discharge pipe end height | Terminate not more than 2 ft (610 mm) and not less than 6 in (152 mm) above ground/flood level, pointing down | CPC § 608.5 / § 1206.2 |
| Discharge piping constraints | No valves/obstructions; same size as valve outlet; cannot be trapped or threaded; visible termination | CPC § 608.5 / § 1206.2 |
| Discharge into pan | Prohibited (relief valve discharge into water heater pan not allowed) | CPC § 507.5 / § 608.5 |
| Expansion control (if check valve/backflow) | Approved, listed, adequately sized expansion tank or approved relief device (exceptions for small instantaneous units) | CPC § 608.3 |
3) Installation, accessibility & equipment hazards
- Appliances must be supported and located to avoid structural or operational hazards; the CHBC's general appliance safety requirement requires installations not to create safety hazards and refers to regular code criteria for venting, combustion air and clearances (§ 8‑902.9.1) .
- Listed water heaters must be installed per their listing and manufacturer's instructions; unlisted units require minimum clearances and AHJ approval (see regular code) .
- The enforcing agency (AHJ) may require operational tests or accept alternatives that provide reasonably equivalent life safety in historical buildings; coordinate with the AHJ early for deviations or preservation constraints .
Exceptions & special cases
- Non‑storage (instantaneous) water heaters that are listed nonstorage instantaneous heaters having an inside diameter of not more than 3 inches (80 mm) may be excepted from the combination T&P valve requirement per the Plumbing Code exception (the CHBC defers to the regular code) .
- Existing systems that, in the enforcing agency’s opinion, do not constitute a safety hazard may remain in use — the CHBC allows the AHJ discretion for existing historical installations (§ 8‑903.1.2) .
- The CHBC allows the AHJ to approve alternatives that achieve reasonably equivalent life safety; where historic fabric restricts installation of modern equipment, obtain AHJ pre‑approval and document the equivalency (§ 8‑903.1.3) .
Common mistakes
- Installing a T&P valve but adding a shutoff valve or trap on the discharge piping (this is not allowed) — discharge piping must have no valves or means of isolation and must be full size to the valve outlet .
- Terminating the T&P discharge into a heater drain pan or concealed space — discharge into a pan is prohibited; termination must be visible and directed to an approved location or outside .
- Using a relief valve set below the building water service pressure or above 150 psi — the relief valve must be set greater than water service pressure and not exceed 150 psi .
- Forgetting to provide thermal expansion control (expansion tank) when a check valve or backflow preventer is present — this can cause repeated relief valve discharge and pressure problems; CPC § 608.3 applies .
- Not coordinating with the AHJ on historic preservation constraints — CHBC requires the AHJ to accept alternatives that provide equivalent life safety; get approvals early (§ 8‑903.1.3) .
Worked example — concrete scenario with numbers
Scenario: Replace/inspect a 50‑gallon storage water heater in a qualified historical building.
- CHBC trigger: Because the building is covered by the CHBC, installation must "create no safety hazard" (§ 8‑902.9.1) and storage heaters must have a T&P device per CHBC (§ 8‑902.9.2) .
- Device: Install an approved combination temperature‑and‑pressure relief valve on the water heater per the Plumbing Code (CPC § 608.3/505.2) .
- Valve setting: If the house water service pressure is 60 psi, select a relief valve set above 60 psi but ≤ 150 psi (e.g., standard 75 psi or 150 psi depending on system needs) — code requires valve setting greater than service pressure and not more than 150 psi (CPC § 608.4) .
- Discharge piping: Use pipe equal to the valve outlet (often 3/4" NPT) and route the pipe full‑size by gravity to the outside, terminating not more than 2 ft (610 mm) and not less than 6 in (152 mm) above finished grade, pointing down and readily visible; do not thread the terminal, do not install a shutoff, and do not trap the piping (CPC § 608.5) .
- Thermal expansion: If a backflow preventer or check valve exists on the building supply (or if design traps pressure), install an approved, sized expansion tank on the cold water side downstream of the backflow device (CPC § 608.3) to prevent repeated relief valve discharge .
- Documentation: Record installation details and, if historic preservation prevents ideal routing or external discharge, submit an equivalency proposal to the AHJ per CHBC § 8‑903.1.3 for review .
Related provisions (CHBC + directly referenced regular code)
- CHBC § 8‑902.9.1 — Appliances/equipment must be installed so no safety hazard is created (includes water heaters) .
- CHBC § 8‑902.9.2 — Storage‑type water heaters shall be equipped with a temperature‑and‑pressure‑relief valve per the regular code .
- CHBC § 8‑903.1 — Plumbing systems shall comply with the regular code unless otherwise noted; includes AHJ discretion for existing systems .
- California Plumbing Code § 608.3 — Expansion tanks and combination T&P requirements (applies where CHBC defers to regular code) .
- California Plumbing Code § 608.4 / § 504.4 — Pressure relief device pressure limits (≤ 150 psi) and overpressure protection rules .
- California Plumbing Code § 608.5 / § 1206.2 — Discharge piping, sizes, termination heights, and prohibitions (no valve/trap; visible termination; no discharge into pans) .
- California Plumbing Code § 505.2 / § 504.6 — Safety device and overtemperature provisions for water heaters referenced by the CHBC .
Code references
Grounded in the retrieved California Historical Building Code — click a citation to read the verbatim passage:
CHBC § 8-902.8.1 High relevance — show source text
MECHANICAL, PLUMBING AND ELECTRICAL REQUIREMENTS
8-902.8.1 Ventilating systems shall be installed so that no safety hazard is created.
8-902.8.2 Grease hoods and grease hood exhaust systems shall be furnished and installed in accordance with applicable requirements of the regular code. Existing systems which are altered shall comply with the regular code.
8-902.9 Miscellaneous equipment requirements.
8-902.9.1 The following appliances and equipment shall be installed so that no safety hazard is created: warm air furnaces, space heating equipment, vented decorative appliances, floor furnaces, vented wall furnaces, unit heaters, room heaters, absorption units, refrigeration equipment, duct furnaces, infrared radiant heaters, domestic incinerators, miscellaneous heat-producing appliances and water heaters.
8-902.9.2 Storage-type water heaters shall be equipped with a temperature- and pressure-relief valve in accordance with applicable requirements of the regular code.
SECTION 8-903 — PLUMBING
8-903.1 General. Plumbing systems shall comply with the regular code unless otherwise noted.
8-903.1.1 The provisions of the CHBC shall apply to the acceptance, location, installation, alteration, repair, relocation, replacement or addition of any plumbing system or equipment within or attached to a historical building.
8-903.1.2 Existing systems which do not, in the opinion of the enforcing agency, constitute a safety hazard may remain in use.
8-903.1.3 The enforcing agency may approve any alternative to these regulations which achieves reasonably equivalent life safety.
8-903.2 Residential occupancies.
8-903.2.1 Where toilet facilities are provided, alternative sewage disposal methods may be acceptable if approved by the local health department. In hotels, where private facilities are not provided, water closets at the ratio of one for each 15 rooms may be acceptable.
8-903.2.2 Toilet facilities are not required to be on the same floor or in the same building as sleeping rooms. Water-flush toilets may be located in a building immediately adjacent to the sleeping rooms. When alternative sewage disposal methods are utilized, they shall be located a minimum distance from the sleeping rooms or other locations as approved by the local health department.
8-903.2.3 Kitchen sinks shall be provided in all kitchens. The sink and countertop may be of any smooth nonabsorbent finish which can be maintained in a sanitary condition.
8-903.2.4 Hand washing facilities shall be provided for each dwelling unit and each hotel guest room. A basin and pitcher may be acceptable as adequate hand washing facilities.
8-903.2.5 Hot or cold running water is not required for each plumbing fixture, provided a sufficient amount of water is supplied to permit the fixture’s normal operation.
8-903.2.6 Bathtubs and lavatories with filler spouts less than 1 inch (25.4 mm) above the fixture rim may remain in use, provided there is an acceptable overflow below the rim.
8-903.2.7 Original or salvage water closets, urinals and flushometer valves shall be permitted in qualified historical buildings or properties. Historically accurate reproduction, nonlow-consumption water closets, urinals and flushometer valves shall be permitted except where historically accurate fixtures that comply with the regular code are available.
CHBC § 8-902.5 High relevance — show source text
8-902.5 Combustion air.
8-902.5.1 All fuel-burning appliances and equipment shall be provided a sufficient supply of air for proper fuel combustion, ventilation and draft hood dilution.
8-902.5.2 The enforcing agency may require operational tests for combustion air systems which do not comply with applicable requirements of the regular code.
8-902.6 Venting of appliances.
8-902.6.1 Every appliance required to be vented shall be connected to an approved venting system. Venting systems shall develop a positive flow adequate to convey all combustion products to the outside atmosphere.
8-902.6.2 Masonry chimneys in structurally sound condition may remain in use for all fuel-burning appliances, provided the flue is evaluated and documentation provided that the masonry and grout are in good condition. Terra cotta chimneys and Type C metallic vents installed in concealed spaces shall not remain in use unless otherwise mitigated and approved on a case-by-case basis.
8-902.6.3 The enforcing agency may require operational tests for venting systems which do not comply with applicable requirements of the regular code.
8-902.7 Ducts.
8-902.7.1 New ducts shall be constructed and installed in accordance with applicable requirements of the regular code.
8-902.7.2 Existing duct systems which do not comply with applicable requirements of the regular code and do not, in the opinion of the enforcing agency, constitute a safety or health hazard may remain in use.
8-902.8 Ventilating systems.
2025 CALIFORNIA HISTORICAL BUILDING CODE 19
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
MECHANICAL, PLUMBING AND ELECTRICAL REQUIREMENTS
8-902.8.1 Ventilating systems shall be installed so that no safety hazard is created.
8-902.8.2 Grease hoods and grease hood exhaust systems shall be furnished and installed in accordance with applicable requirements of the regular code. Existing systems which are altered shall comply with the regular code.
8-902.9 Miscellaneous equipment requirements.
8-902.9.1 The following appliances and equipment shall be installed so that no safety hazard is created: warm air furnaces, space heating equipment, vented decorative appliances, floor furnaces, vented wall furnaces, unit heaters, room heaters, absorption units, refrigeration equipment, duct furnaces, infrared radiant heaters, domestic incinerators, miscellaneous heat-producing appliances and water heaters.
8-902.9.2 Storage-type water heaters shall be equipped with a temperature- and pressure-relief valve in accordance with applicable requirements of the regular code.
SECTION 8-903 — PLUMBING
8-903.1 General. Plumbing systems shall comply with the regular code unless otherwise noted.
8-903.1.1 The provisions of the CHBC shall apply to the acceptance, location, installation, alteration, repair, relocation, replacement or addition of any plumbing system or equipment within or attached to a historical building.
8-903.1.2 Existing systems which do not, in the opinion of the enforcing agency, constitute a safety hazard may remain in use.
8-903.1.3 The enforcing agency may approve any alternative to these regulations which achieves reasonably equivalent life safety.
8-903.2 Residential occupancies.
CHBC § 505.0 High relevance — show source text
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:
(1) The heat transfer medium shall be either potable water or contain fluids recognized as safe by the Food and Drug Administration (FDA) as food grade.
(2) Bear a label with the word “Caution,” followed by the following statements:
(a) The heat-transfer medium shall be potable water or other nontoxic fluid recognized as safe by the FDA.
(b) The maximum operating pressure of the heat exchanger shall not exceed the maximum operating pressure of the potable water supply.
(3) The word “Caution” and the statements in letters shall have an uppercase height of not less than 0.120 of an inch (3.048 mm). The vertical spacing between lines of type shall be not less than 0.046 of an inch (1.168 mm). Lowercase letters shall be compatible with the uppercase letter size specification.
506.0 Air for Combustion and Ventilation.
506.1 General. Air for combustion, ventilation, and dilution of flue gases for appliances installed in buildings shall be obtained by application of one of the methods covered in Section 506.2 through Section 506.7.3. Where the requirements of Section 506.2 are not met, outdoor air shall be introduced in accordance with methods covered in Section 506.4 through Section 506.7.3.
Exception: This provision shall not apply to direct vent appliances. {NFPA 54:9.3.1.1} 506.1.1 Other Types of Appliances. Appliances of other than natural draft design, appliances not designated as Category I vented appliances, and appliances equipped with power burners shall be provided with combustion, ventilation, and dilution air in accordance with the appliance manufacturer’s instructions. [NFPA 54:9.3.1.2]
CHBC § 1205.3 High relevance — show source text
Note: [HCD 1 & HCD 2] PEX-AL-PEX is not adopted in the California Plumbing Code for use in potable water supply and distribution systems. (2) Copper tubing shall be tested at not less than 80 psi (552 kPa). 1205.3 Flushing. Heating and cooling sources, system piping and tubing shall be flushed after installation with water or a cleaning solution. Cleaning and flushing of the heating and cooling sources shall comply with the manufacturer’s instructions. The cleaning solution shall be compatible with all system components and shall be used in accordance with the manufacturer’s instructions.
1206.0 Pressure and Safety Devices. 1206.1 General. Each closed hydronic system shall be protected against pressures exceeding design limitations with not less than one pressure relief valve. Each closed section of the system containing a heat source shall have a relief valve located so that the heat source is not capable of being isolated from a relief device. Pressure relief valves shall be installed in accordance with their listing and the manufacturer’s installation instructions.
1206.2 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 (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 visible.
1207.0 Heating Appliances and Equipment. 1207.1 General. Heating appliances, equipment, safety and operational controls shall be listed for its intended use in a hydronic heating system and installed in accordance with the manufacturer’s installation instructions.
1207.2 Boilers. Boilers and their control systems shall comply with Section 1002.0. 1207.2.1 Condensing Boilers. A condensing boiler, in which the heat exchanger and venting system are designed to operate with condensing flue gases, shall be permitted to be connected directly to the panel heating system without a protective mixing device. 1207.2.2 Noncondensing Boilers. Where the heat exchanger and venting system are not designed to operate with condensed flue gases, the boiler shall be permitted to connect directly to the panel heating system where protected from flue gas condensation. The operating temperature of the boiler shall be more than the fluid temperature in accordance with the manufacturer’s instructions. The minimum return-water temperature to the heat source shall comply with Section 1201.5.
CHBC § 608.3 High 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.
CHBC § 501.1 Medium 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
California Historical Building Code Medium relevance — show source text
100
| |600
|72
|151
|284
|583
|873
|1680
|2680
|4740
|9660
| |650
|69
|144
|272
|558
|836
|1610
|2570
|4540
|9250
| |700
|66
|139
|261
|536
|803
|1550
|2470
|4360
|8890
| |750
|64
|134
|252
|516
|774
|1490
|2380
|4200
|8560
| |800
|62
|129
|243
|499
|747
|1440
|2290
|4050
|8270
| |850
|60
|125
|235
|483
|723
|1390
|2220
|3920
|8000
| |900
|58
|121
|228
|468
|701
|1350
|2150
|3800
|7760
| |950
|56
|118
|221
|454
|681
|1310
|2090
|3690
|7540
| |1000
|55
|114
|215
|442
|662
|1280
|2030
|3590
|7330
| |1100
|52
|109CHBC § 9.3 Medium relevance — show source text
9.3**|SDR 11|SDR 11|SDR 10|SDR 11|SDR 11|SDR 11|SDR 11| |ACTUAL ID:|0.660|0.860|1.077|1.328|1.554|1.943|2.864|3.682| |LENGTH (feet)
|CAPACITY IN THOUSANDS OF BTU PER HOUR
|CAPACITY IN THOUSANDS OF BTU PER HOUR
|CAPACITY IN THOUSANDS OF BTU PER HOUR
|CAPACITY IN THOUSANDS OF BTU PER HOUR
|CAPACITY IN THOUSANDS OF BTU PER HOUR
|CAPACITY IN THOUSANDS OF BTU PER HOUR
|CAPACITY IN THOUSANDS OF BTU PER HOUR
|CAPACITY IN THOUSANDS OF BTU PER HOUR
| |10
|340
|680
|1230
|2130
|3210
|5770
|16 000
|30 900
| |20
|233
|468
|844
|1460
|2210
|3970
|11 000
|21 200
| |30
|187
|375
|677
|1170
|1770
|3180
|8810
|17 000
| |40
|160
|321
|580
|1000
|1520
|2730
|7540
|14 600
| |50
|142
|285
|514
|890
|1340
|2420
|6680
|12 900
| |60
|129
|258
|466
|807
|1220
|2190
|6050
|11 700
| |70
|119
|237
|428
|742
|1120
|2010
|5570
|10 800
| |80
|110
|221
|398
|690
|1040
|1870
|5180
|10 000
| |90
|103
|207
|374
|648
|978
|1760
|4860
|9400
| |100
|98
|196
|353
|612
|924
|1660
|4590
|8900<California Historical Building Code Medium relevance — show source text
|1280
|2030
|3590
|7330
| |550
|52
|109
|204
|420
|629
|1210
|1930
|3410
|6960
| |600
|50
|104
|195
|400
|600
|1160
|1840
|3260
|6640
| |650
|47
|99
|187
|384
|575
|1110
|1760
|3120
|6360
| |700
|46
|95
|179
|368
|552
|1060
|1690
|3000
|6110
| |750
|44
|92
|173
|355
|532
|1020
|1630
|2890
|5890
| |800
|42
|89
|167
|343
|514
|989
|1580
|2790
|5680
| |850
|41
|86
|162
|332
|497
|957
|1530
|2700
|5500
| |900
|40
|83
|157
|322
|482
|928
|1480
|2610
|5330
| |950
|39
|81
|152
|312
|468
|901
|1440
|2540
|5180
| |1000<bCHBC § 3.785 Medium relevance — show source text
SYSTEM VOLUME2
(gallons)TANK CAPACITY
DIAPHRAGM TYPE
(gallons)TANK CAPACITY NON-
DIAPHRAGM TYPE
(gallons)
1009 15
20017 30
30025 45
40033 60
50042 75
100083 150
2000165 300 For SI units: 1 gallon = 3.785 L
Notes: 1 Based on an average operating water temperature of 195°F (91°C), a fill pressure of 12 psig (83 kPa), and an operating pressure of not more than 30 psig (207 kPa). 2 Includes volume of water in boiler, radiation, and piping, not including expansion tank.
1005.0 Safety or Relief Valve Discharge.
1005.1 General. Pressurized vessels or boilers shall be provided with overpressure protection by means of a listed pressure relief valve installed in accordance with the manufacturer’s
installation instructions.
1005.2 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 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 (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) Discharge to a termination point that is readily visible.
1005.3 Splash Shield. Where the operating temperature exceeds 212°F (100°C), the discharge pipe shall be installed with a splash shield or centrifugal separator.
1005.4 Hazardous Discharge. Where the discharge from safety valves is capable of being hazardous, discharge of steam inside the boiler room, such discharge shall be discharged to the outside of the boiler room. Discharges from relief valves on industrial boilers shall be discharged to an approved location.
1005.5 Vacuum Relief Valve. Hot-water heating systems that are subjected to a vacuum while in operation or during shutdown shall be protected with a vacuum relief valve that complies with ANSI Z21.22/CSA 4.4. Where the piping configuration, equipment location, and valve outlets are located below the boiler elevation, the system shall be equipped with a vacuum relief valve at the highest point.
1006.0 Shutoff Valves.
CHBC § 54-2018 Medium 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:
CHBC § 610.4. Medium relevance — show source text
** Where static water pressure in the water supply piping exceeds 80 psi (552 kPa), an approved-type pressure regulator preceded by an adequate strainer shall be installed and the static pressure reduced to 80 psi (552 kPa) or less. Pressure regulators for potable water distribution systems shall comply with ASSE 1003 or AWWA C530. Pressure regulator(s) equal to or exceeding 1 [1] ⁄ 2 inches (40 mm) shall not require a strainer. Such regulator(s) shall control the pressure to water outlets in the building unless otherwise approved by the Authority Having Jurisdiction. Each such regulator and strainer shall be accessibly located aboveground or in a vault equipped with a properly sized and sloped boresighted drain to daylight, shall be protected from freezing, and shall have the strainer readily accessible for cleaning without removing the regulator or strainer body or disconnecting the supply piping. Pipe size determinations shall be based on 80 percent of the reduced pressure where using Table 610.4.
An approved expansion tank shall be installed in the cold water distribution piping downstream of each such regulator to prevent pressure exceeding 80 psi from developing due to thermal expansion. Expansion tanks used in potable water systems intended to supply drinking water shall comply with NSF/ANSI/CAN 61. 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.
Frequently asked questions
Do I always need a T&P valve on a water heater in a CHBC building?
Yes — storage‑type water heaters must have a temperature‑and‑pressure relief valve as required by § 8‑902.9.2; the CHBC defers the technical installation details to the regular plumbing code (CPC) .
Can the T&P discharge go into the water‑heater pan or attic drain?
No. The Plumbing Code (which the CHBC references) prohibits discharging a relief valve into a water‑heater pan; discharge must go to an approved location or outside and be readily visible (CPC § 507.5 / § 608.5) .
What if the historic fabric prevents running a visible external discharge pipe?
The CHBC allows the Authority Having Jurisdiction to approve alternatives that achieve reasonably equivalent life safety (see CHBC § 8‑903.1.3). Engage the AHJ early and submit an alternative plan demonstrating equivalent protection .
Is a relief valve setting of 200 psi allowed?
No. The Plumbing Code sets a maximum pressure relief valve setting of 150 psi; the relief setting must also be greater than the building water service pressure (CPC § 608.4 / § 504.4) .
Do I need an expansion tank if I install a backflow preventer?
Yes — if the system prevents dissipation of thermal expansion into the water main (check valve/backflow device), an approved, adequately sized expansion tank or other approved device is required (CPC § 608.3) unless an allowed alternative relief device is used and listed appropriately .
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