CRC · California Residential Code

Backflow prevention and cross-connection control

Homeowner summary: The plumbing code requires any pipe that fills a tank, pool, sump or similar receptacle be protected so dirty water cannot flow back into your drinking water — usually by an air gap, a listed vacuum breaker mounted at least 6 inches above the outlet, or a backflow device sized for the hazard; these devices must be installed per the Plumbing Code and tested at installation and at least yearly. file

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Last reviewed: July 6, 2026

What the code requires — plain English

The California plumbing rules require that water supply inlets to tanks, vats, sumps, swimming pools and other receptors must be protected from backflow either by an approved air gap, a listed vacuum breaker with the critical level not less than 6 inches, or a backflow preventer suitable for the degree of hazard. This requirement is stated in § 603.5.5 of the (California) Plumbing Code.

Note: the California Residential Code (CRC) incorporates plumbing safety by reference to the California Plumbing Code for cross‑connection and backflow requirements; plumbing Chapter 603 (including § 603.5.5) is the controlling text for these protections.

The simplest rule: protect any supply inlet to a vessel by an air gap, a listed vacuum breaker (critical level ≥ 6 inches), or a backflow device rated for the hazard — don’t allow a direct unprotected inlet.

Key defined terms (first use)

  • Backflow and Backsiphonage — defined in the code and are the conditions the rules prevent.
  • Backflow preventer (including reduced‑pressure principle, pressure vacuum breaker, etc.) — types and definitions appear in Chapter 603.

Requirements in detail

Core requirement for water‑supply inlets

For any water supply inlet to a tank, sump, pool, vat or similar receptor, the installer must use one of these three methods (see § 603.5.5):

  • An approved air gap.
  • A listed vacuum breaker installed on the discharge side of the last valve with the critical level not less than 6 inches (152 mm) or per its listing.
  • A backflow preventer suitable for the degree of hazard, installed in accordance with the chapter’s requirements for that device type (see Table 603.2 and the device definitions).

Who approves devices & testing

  • Devices/assemblies must be acceptable to the Authority Having Jurisdiction and comply with listed standards; backflow assemblies must be tested at installation and at least annually by a certified tester (see Chapter 603 general and testing rules).

Decision table — selecting the protection for a supply inlet

Situation / Dimension Typical acceptable method(s) Key value or note Code Reference
Receptor inlet where an air gap can be provided Air gap Follow minimums in Table 603.3.1 § 603.5.5; Table 603.3.1
No practicable air gap; intermittent or occasional pressure only Listed vacuum breaker (on discharge side of last valve) Critical level ≥ 6 in (152 mm) or as listed § 603.5.5
Potential contamination or backpressure (degree of hazard) Backflow preventer selected per hazard (e.g., DC, RP, PVB) Choose device per Table 603.2 § 603.5.5; Table 603.2
Pool or large tank with pumps/chemicals Reduced‑pressure principle (RP) or other as Table 603.2 dictates RP required when chemicals or high hazard present Table 603.2; § 603.5.10/603.5.6
Hose bibbs / hose attachments Nonremovable hose‑bibb backflow preventer, nonremovable vacuum breaker, or AVB ≥ 6 in above highest usage Frost‑proof versions required in freezing climates § 603.5.7

(See Table 603.2 for device‑to‑hazard mapping and Table 603.3.1 for air‑gap minimums.)

Installation & maintenance highlights

  • Backflow assemblies must be accessible with required clearance (manufacturer’s instructions; not less than 12 inches (305 mm) between lowest part and grade/floor). Testing access/platform provisions where assemblies exceed 5 ft.
  • Assemblies must be field‑tested at installation, repair, relocation and not less than an annual schedule thereafter by a certified backflow assembly tester.

Exceptions & special cases

  • Some fixtures/systems have tailored rules: water‑closet tanks and flushometer tanks have specific backflow/ballcock requirements (§ 603.5.2–.3).
  • Irrigation/lawn sprinkler systems without pumps or chemical injectors may use AVB, PVB, SVB, RP or a valve complying with IAPMO PS 72; systems with pumps or chemical injectors have stricter device requirements (see § 603.5.6 and subparts).
  • Where correction of individual cross‑connections is impracticable, the code permits identifying a line as nonpotable and requires labeling and isolation of outlets (see § 603.5.11).
  • Fire‑protection systems have their own rules: potable connections to sprinklers must be protected by DC or RP assemblies; if chemicals/antifreeze are used, RP protection is required (see R‑sections in the Residential Code for sprinklers and the Plumbing Code provisions).

If you need a jurisdictional exception or local amendment, consult the Authority Having Jurisdiction — the code requires device approval by that authority.

Common mistakes

  • Relying on a check valve or ad hoc fitting instead of a listed/approved backflow assembly. The code requires listed devices and acceptance by the AHJ.
  • Installing a vacuum breaker with the wrong orientation or under continuous pressure when the device isn’t listed for that use (many AVBs are not for continuous pressure). Always follow the device listing and manufacturer instructions.
  • Confusing air‑gap measurement points — air gaps must meet the minimums in Table 603.3.1 and be measured per the table rules (effective opening, walls/ribs exceptions).
  • Omitting annual testing and recordkeeping — assemblies must be tested at installation/repair and at least annually by a certified tester.
  • Using hose bibb vacuum breakers below the minimum mounting height (they often require installation above the highest point of use). See § 603.5.7.

Worked example — pool fill inlet

Scenario: You are installing the potable water fill line to a new in‑ground swimming pool. The pool will be filled from the domestic supply and the pool will be chlorinated (chemicals present).

Step 1 — Identify the hazard: Pool water includes chemicals and is a large receptor; potential contamination = high hazard. (If chemicals are present, the degree of hazard is high and backpressure can exist.)

Step 2 — Options per § 603.5.5: air gap, listed vacuum breaker (critical level ≥ 6 inches), or a backflow preventer suitable for the degree of hazard. Because chemicals are introduced, an air gap or a reduced‑pressure principle backflow prevention assembly (RP) is appropriate (Table 603.2 indicates RP for high hazard/contamination).

Step 3 — Practical choice & dimensions:

  • If you can route the fill pipe so the outlet is above the pool flood‑level rim and provide an air gap equal to at least the required table minimum (see Table 603.3.1), you may use an air gap. If the fill piping is 1.5 in. OD, an air gap of at least the table‑specified amount (and measured per Table 603.3.1 rules) is required.
  • If space or routing doesn’t permit an acceptable air gap, install a reduced‑pressure principle backflow prevention assembly (RP) on the supply side and provide required access and annual testing (clearance ≥ 12 in. to floor/grade; tester certified to ASSE/IAPMO/ANSI Series 5000).

Result: Because chlorine is used (chemical injection), the code‑preferred and commonly required solution is an RP assembly installed upstream of the pool fill line, with annual testing by a certified tester.

Related provisions (select sections to read)

  • § 603.5.5 — Water Supply Inlets (primary controlling provision cited above).
  • § 603.0 / § 603.1 — Cross‑Connection Control general requirements and scope.
  • § 603.2 — Approval of devices or assemblies; Table 603.2 maps device types to hazard levels.
  • § 603.3.1 and Table 603.3.1 — Air‑gap minimums and measurement rules.
  • § 603.4.2 — Testing frequency and certified tester requirement (installation, repair, relocation, and at least annually).
  • § 603.5.6 — Protection for lawn sprinkler and irrigation systems (special rules for pumps, chemical injectors).
  • § 603.5.7 — Outlets with hose attachments (requirements for hose‑bib protection and frost‑proof units).
  • CRC definitions for Backflow, Backsiphonage, and Backflow Preventer (see Residential Code definitions).

NOTE: The CRC text indicates that Part VII—Plumbing is not adopted in the Residential Code and that plumbing provisions are found in the California Plumbing Code; therefore, the plumbing sections listed above are the authoritative requirements for backflow/cross‑connection protection in residential applications.

(Plain disclosure) I was unable to locate a discrete text block labeled § 601.0 in the materials you uploaded. If you intended a specific § 601.0 (Residential Code or Plumbing Code) as the other controlling citation, please upload that file or point me to the text; I will incorporate it exactly. I relied on the available Chapter 603 text (including § 603.5.5) to ground each requirement above.

Code references

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

  • CRC § 91761-2816 High relevance — show source text

    Education and Training Seminars: IAPMO specializes in conducting training and education, including fulfilling continuing education requirements, on the UPC and UMC as well as all of the most commonly utilized codes in the Construction Trades. Special seminars on industry or code subjects are expeditiously created and delivered upon request. Please call to obtain the seminar schedule or to arrange for a custom special seminar.

    Backflow Prevention Institute – IAPMO:

    The IAPMO Backflow Prevention Institute provides professional education and training for the control of hazards to our water supply and is dedicated to water-system safety worldwide. The Institute provides training in backflow prevention and cross-connection control. This program includes backflow preventers, testers, repairers, cross-connection control surveyors, program administrators and fire-sprinkler backflow preventer testers. Each of these courses provides compliance certification to American Society of Sanitary Engineering (ASSE) Series 5000 Professional Qualification Standards.

    Backflow Prevention Reference Manual:

    This unique 300-page manual contains full-color illustrations and sections relating to real-world installations, backflow prevention, testing cross-connection control, repair and inspections. The manual is an excellent textbook and a reference the inspectors in every jurisdiction should have access too. It is also an important resource for system designers, urban planners and utility companies – professionals on both sides of the water meter.

    ANSI Z124 Standards:

    These standards are written to specifically address a variety of plastic plumbing fixtures and components. They are available individually, or may be grouped for quantity discounts.

    IAPMO Installation Standards:

    IAPMO standards committees have formulated installation standards for a wide variety of commonly used plumbing materials and systems. The IAPMO installation standards are included after the text of the Uniform Plumbing Code, or can be purchased separately.

    xxiv 2025 CALIFORNIA MECHANICAL CODE

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

    RELATED PUBLICATIONS AND SERVICES

    The Documents Listed are Not by this Reference Adopted by The State of California.

    Material and Property Standards: IAPMO does not generally develop material and property standards, but when a need exists the Association will take a leadership role by filling the void. They are available, are subject to amendments and are withdrawn when recognized consensus standards are formulated.

    OFFICIAL Magazine: IAPMO’s quarterly publication features informative articles related to Plumbing and Mechanical HVACR installations, award winning general interest features, technical columns and industry updates. Subscriptions are available and all IAPMO members receive a free copy of every issue!

    Membership in IAPMO: IAPMO membership is open to all interested persons. Membership categories include Student, Individual, Senior, Organizational and Governmental. Member benefits include discounted prices on IAPMO publications, a subscription to Official magazine, and numerous educational and training opportunities.

    HOW TO CONTACT IAPMO

    Mailing Address: 4755 East Philadelphia Street, Ontario, California 91761-2816

    Main Number: 909-472-4100 • Publication Orders: 800-85-IAPMO • Publication Fax: 877-85-CODES

    Website: www.iapmo.org • Office Hours: Monday – Friday, 8am – 5pm Pacific Time

    2025 CALIFORNIA MECHANICAL CODE xxv

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

    xxvi 2025 CALIFORNIA MECHANICAL CODE

  • CRC § 602.0 High relevance — show source text

    602.0 Unlawful Connections.

    602.1 Prohibited Installation. No installation of potable water supply piping, or part thereof, shall be made in such a manner that it will be possible for used, unclean, polluted, or contaminated water, mixtures, or substances to enter a portion of such piping from a tank, receptor, equipment, or plumbing fixture by reason of backsiphonage, suction, or other cause, either during normal use and operation thereof, or where such tank, receptor, equipment, or plumbing fixture is flooded or subject to pressure exceeding the operating pressure in the hot or cold water piping. 602.2 Cross-Contamination. No person shall make a connection or allow one to exist between pipes or conduits carrying domestic water supplied by a public or private building supply system, and pipes, conduits, or fixtures containing or carrying water from any other source or containing or carrying water that has been used for any purpose whatsoever, or piping carrying chemicals, liquids, gases, or substances whatsoever, unless there is provided a backflow prevention device approved for the potential hazard and maintained in accordance with this code. Each point of use shall be separately protected where potential cross-contamination of individual units exists.

    602.3 Backflow Prevention. No plumbing fixture, device, or construction shall be installed or maintained, or shall be connected to a domestic water supply, where such installation or connection provides a possibility of polluting such water supply or cross-connection between a distributing system of water for drinking and domestic purposes and water that becomes contaminated by such plumbing fixture, device, or construction unless there is provided a backflow prevention device approved for the potential hazard.

    602.4 Approval by Authority. No water piping supplied by a private water supply system shall be connected to any other source of supply without the approval of the Authority Having Jurisdiction, Health Department, or other department having jurisdiction.

    603.0 Cross-Connection Control.

    603.1 General. Cross-connection control shall be provided in accordance with the provisions of this chapter.

    No person shall install a water-operated equipment or mechanism, or use a water-treating chemical or substance, where it is found that such equipment, mechanism, chemical, or substance causes pollution or contamination of the domestic water supply. Such equipment or mechanism shall be permitted where equipped with an approved backflow prevention device or assembly.

    603.2 Approval of Devices or Assemblies. Before a device or an assembly is installed for the prevention of backflow, it shall have first been approved by the Authority Having Jurisdiction. Devices or assemblies shall be tested in accordance with recognized standards or other standards acceptable to the Authority Having Jurisdiction. Backflow prevention devices and assemblies shall comply with Table 603.2, except for specific applications and provisions as stated in Section 603.5.1 through Section 603.5.22.

    2025 CALIFORNIA PLUMBING CODE 139

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

    WATER SUPPLY AND DISTRIBUTION

  • CMC § 2025 High relevance — show source text

    Guide to Important Code Questions to the Uniform Plumbing Code:

    An excellent reference for learning and understanding plumbing code changes and identifies code changes between editions. It is a useful tool for preparing code change proposals.

    2025 CALIFORNIA MECHANICAL CODE xxiii

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

    RELATED PUBLICATIONS AND SERVICES

    The Documents Listed are Not by this Reference Adopted by The State of California.

    Uniform Swimming Pool, Spa, and Hot Tub Code – 2024 Edition: The Uniform Swimming Pool, Spa and Hot Tub Code contains complete and current requirements for the erection, installation, alteration, repair, relocation, replacement, addition to and use or maintenance of these systems.

    Uniform Solar, Hydronics and Geothermal Code – 2024 Edition: The Uniform Solar, Hydronics and Geothermal Code contains complete requirements for the erection, installation, alteration, addition, repair, relocation, replacement, addition to, use or maintenance of these systems.

    Drain Waste and Vent Calculator:

    A slide-rule style calculator provides quick and simple access to the fixture unit and sizing tables of Chapter 7 of the UPC.

    Water Sizing Calculator: Sizing water systems becomes a much simpler task with the use of this handy slide-rule style calculator.

    Natural Gas Pipe Sizing Calculator: This Natural Gas Pipe Sizing Calculator is presented in an easy to use and read slide-rule format. Designed for systems with a supply pressure of six to eight inches of water column, all pipe capacities are given in cubic feet per hour.

    Trailer Standards:

    IAPMO has developed a number of standards for specialty products used in manufactured homes and recreational vehicles. These standards are available individually, or they may be purchased as a set.

    Education and Training Seminars: IAPMO specializes in conducting training and education, including fulfilling continuing education requirements, on the UPC and UMC as well as all of the most commonly utilized codes in the Construction Trades. Special seminars on industry or code subjects are expeditiously created and delivered upon request. Please call to obtain the seminar schedule or to arrange for a custom special seminar.

    Backflow Prevention Institute – IAPMO:

    The IAPMO Backflow Prevention Institute provides professional education and training for the control of hazards to our water supply and is dedicated to water-system safety worldwide. The Institute provides training in backflow prevention and cross-connection control. This program includes backflow preventers, testers, repairers, cross-connection control surveyors, program administrators and fire-sprinkler backflow preventer testers. Each of these courses provides compliance certification to American Society of Sanitary Engineering (ASSE) Series 5000 Professional Qualification Standards.

    Backflow Prevention Reference Manual:

    This unique 300-page manual contains full-color illustrations and sections relating to real-world installations, backflow prevention, testing cross-connection control, repair and inspections. The manual is an excellent textbook and a reference the inspectors in every jurisdiction should have access too. It is also an important resource for system designers, urban planners and utility companies – professionals on both sides of the water meter.

    ANSI Z124 Standards:

    These standards are written to specifically address a variety of plastic plumbing fixtures and components. They are available individually, or may be grouped for quantity discounts.

    IAPMO Installation Standards:

    IAPMO standards committees have formulated installation standards for a wide variety of commonly used plumbing materials and systems. The IAPMO installation standards are included after the text of the Uniform Plumbing Code, or can be purchased separately.

  • CRC § 91761-2816 High relevance — show source text

    Trailer Standards:

    IAPMO has developed a number of standards for specialty products used in manufactured homes and recreational vehicles. These standards are available individually, or they may be purchased as a set.

    Education and Training Seminars: IAPMO specializes in conducting training and education, including fulfilling continuing education requirements, on the UPC and UMC as well as all of the most commonly utilized codes in the Construction Trades. Special seminars on industry or code subjects are expeditiously created and delivered upon request. Please call to obtain the seminar schedule or to arrange for a custom special seminar.

    Backflow Prevention Institute – IAPMO:

    The IAPMO Backflow Prevention Institute provides professional education and training for the control of hazards to our water supply and is dedicated to water-system safety worldwide. The Institute provides training in backflow prevention and cross-connection control. This program includes backflow preventers, testers, repairers, cross-connection control surveyors, program administrators and fire-sprinkler backflow preventer testers. Each of these courses provides compliance certification to American Society of Sanitary Engineering (ASSE) Series 5000 Professional Qualification Standards.

    Backflow Prevention Reference Manual:

    This unique 300-page manual contains full-color illustrations and sections relating to real-world installations, backflow prevention, testing cross-connection control, repair and inspections. The manual is an excellent textbook and a reference the inspectors in every jurisdiction should have access too. It is also an important resource for system designers, urban planners and utility companies – professionals on both sides of the water meter.

    ANSI Z 124 Standards:

    These standards are written to specifically address a variety of plastic plumbing fixtures and components. They are available individually, or may be grouped for quantity discounts.

    IAPMO Installation Standards:

    IAPMO standards committees have formulated installation standards for a wide variety of commonly used plumbing materials and systems. The IAPMO installation standards are included after the text of the Uniform Plumbing Code, or can be purchased separately.

    xxiv 2025 CALIFORNIA PLUMBING CODE

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

    RELATED PUBLICATIONS AND SERVICES

    The Documents Listed are Not by this Reference Adopted by The State of California.

    Material and Property Standards: IAPMO does not generally develop material and property standards, but when a need exists the Association will take a leadership role by filling the void. They are available, are subject to amendments and are withdrawn when recognized consensus standards are formulated.

    OFFICIAL Magazine: IAPMO’s quarterly publication features informative articles related to Plumbing and Mechanical HVACR installations, award winning general interest features, technical columns and industry updates. Subscriptions are available and all IAPMO members receive a free copy of every issue!

    Membership in IAPMO: IAPMO membership is open to all interested persons. Membership categories include Student, Individual, Senior, Organizational and Governmental. Member benefits include discounted prices on IAPMO publications, a subscription to Official magazine, and numerous educational and training opportunities.

    HOW TO CONTACT IAPMO

    Mailing Address: 4755 East Philadelphia Street, Ontario, California 91761-2816

    Main Number: 909-472-4100 • Publication Orders: 800-85-IAPMO • Publication Fax: 877-85-CODES

    Website: www.iapmo.org • Office Hours: Monday – Friday, 8am – 5pm Pacific Time

    2025 CALIFORNIA PLUMBING CODE xxv

  • CMC § 2025 High relevance — show source text

    Uniform Mechanical Code Illustrated Training Manual:

    Contains technical diagrams and illustrations that demonstrate the intent and use of the UMC. A great reference for everyone involved in Mechanical HVACR design and installation.

    Uniform Mechanical Code Study Guide:

    The Study Guide is a complete self-study course for learning the UMC. A big help in getting ready for a certification exam! This book is the perfect complement to the UMC Illustrated Training Manual.

    Guide to Important Code Questions to the Uniform Mechanical Code:

    An excellent reference for learning and understanding mechanical code changes and identifies code changes between editions. It is a useful tool for preparing code change proposals.

    2025 CALIFORNIA PLUMBING CODE xxiii

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

    RELATED PUBLICATIONS AND SERVICES

    The Documents Listed are Not by this Reference Adopted by The State of California.

    Uniform Swimming Pool, Spa, and Hot Tub Code – 2024 Edition: The Uniform Swimming Pool, Spa and Hot Tub Code contains complete and current requirements for the erection, installation, alteration, repair, relocation, replacement, addition to and use or maintenance of these systems.

    Uniform Solar, Hydronics and Geothermal Code – 2024 Edition: The Uniform Solar, Hydronics and Geothermal Code contains complete requirements for the erection, installation, alteration, addition, repair, relocation, replacement, addition to, use or maintenance of these systems.

    Drain Waste and Vent Calculator:

    A slide-rule style calculator provides quick and simple access to the fixture unit and sizing tables of Chapter 7 of the UPC.

    Water Sizing Calculator: Sizing water systems becomes a much simpler task with the use of this handy slide-rule style calculator.

    Natural Gas Pipe Sizing Calculator: This Natural Gas Pipe Sizing Calculator is presented in an easy to use and read slide-rule format. Designed for systems with a supply pressure of six to eight inches of water column, all pipe capacities are given in cubic feet per hour.

    Trailer Standards:

    IAPMO has developed a number of standards for specialty products used in manufactured homes and recreational vehicles. These standards are available individually, or they may be purchased as a set.

    Education and Training Seminars: IAPMO specializes in conducting training and education, including fulfilling continuing education requirements, on the UPC and UMC as well as all of the most commonly utilized codes in the Construction Trades. Special seminars on industry or code subjects are expeditiously created and delivered upon request. Please call to obtain the seminar schedule or to arrange for a custom special seminar.

    Backflow Prevention Institute – IAPMO:

    The IAPMO Backflow Prevention Institute provides professional education and training for the control of hazards to our water supply and is dedicated to water-system safety worldwide. The Institute provides training in backflow prevention and cross-connection control. This program includes backflow preventers, testers, repairers, cross-connection control surveyors, program administrators and fire-sprinkler backflow preventer testers. Each of these courses provides compliance certification to American Society of Sanitary Engineering (ASSE) Series 5000 Professional Qualification Standards.

    Backflow Prevention Reference Manual:

    This unique 300-page manual contains full-color illustrations and sections relating to real-world installations, backflow prevention, testing cross-connection control, repair and inspections. The manual is an excellent textbook and a reference the inspectors in every jurisdiction should have access too. It is also an important resource for system designers, urban planners and utility companies – professionals on both sides of the water meter.

    ANSI Z 124 Standards:

  • CRC § 602.4 High relevance — show source text

    602.4 Approval by Authority. No water piping supplied by a private water supply system shall be connected to any other source of supply without the approval of the Authority Having Jurisdiction, Health Department, or other department having jurisdiction.

    603.0 Cross-Connection Control.

    603.1 General. Cross-connection control shall be provided in accordance with the provisions of this chapter.

    No person shall install a water-operated equipment or mechanism, or use a water-treating chemical or substance, where it is found that such equipment, mechanism, chemical, or substance causes pollution or contamination of the domestic water supply. Such equipment or mechanism shall be permitted where equipped with an approved backflow prevention device or assembly.

    603.2 Approval of Devices or Assemblies. Before a device or an assembly is installed for the prevention of backflow, it shall have first been approved by the Authority Having Jurisdiction. Devices or assemblies shall be tested in accordance with recognized standards or other standards acceptable to the Authority Having Jurisdiction. Backflow prevention devices and assemblies shall comply with Table 603.2, except for specific applications and provisions as stated in Section 603.5.1 through Section 603.5.22.

    2025 CALIFORNIA PLUMBING CODE 139

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

    WATER SUPPLY AND DISTRIBUTION

    Devices or assemblies installed in a potable water supply system for protection against backflow shall be maintained in good working condition by the person or persons having control of such devices or assemblies. Such devices or assemblies shall be tested at the time of installation, repair, or relocation and not less than on an annual schedule thereafter, or more often where required by the Authority Having Jurisdiction. Where found to be defective or inoperative, the device or assembly shall be repaired or replaced. No device or assembly shall be removed from use or relocated or other device or assembly substituted, without the approval of the Authority Having Jurisdiction.

    Testing or maintenance shall be performed by a certified backflow assembly tester or repairer certified in accordance with ASSE/IAPMO/ANSI Series 5000 or any other additional certification approved by the Authority Having Jurisdiction.

    603.3 Backflow Prevention Devices, Assemblies, and Methods. Backflow prevention devices, assemblies, and methods shall comply with Section 603.3.1 through Section 603.3.12.

    603.3.1 Air Gap. The minimum air gap to afford backflow protection shall be in accordance with Table 603.3.1. 603.3.2 Atmospheric Vacuum Breaker (AVB). An atmospheric vacuum breaker consists of a body, a checking member, and an atmospheric port.

    603.3.3 Hose Connection Backflow Preventer. A hose connection backflow preventer consists of two independent check valves with an independent atmospheric vent between and a means of field testing and draining.

    603.3.4 Double Check Valve Backflow Prevention Assembly (DC). A double check valve backflow prevention assembly consists of two independently acting internally loaded check valves, four properly located test cocks, and two isolation valves.

    603.3.5 Pressure Vacuum Breaker Backflow Pre- vention Assembly (PVB). A pressure vacuum breaker backflow prevention assembly consists of a loaded air inlet valve, an internally loaded check valve, two properly located test cocks, and two isolation valves.

  • CRC § 603.2 High relevance — show source text

    Have outlet open to
    atmosphere. Minimum of 6 inches or listed
    distance above all downstream piping and
    flood level rim of receptor.4,5| |Backflow preventer for
    Carbonated Beverage
    Dispensers (two inde-
    pendent check valves
    with a vent to the atmos-
    phere)|ASSE 1022|X|X|X|X|Installation includes carbonated beverage
    machines or dispensers. These devices
    operate under intermittent or continuous
    pressure conditions.| |Backflow preventer with
    intermediate atmos-
    pheric vent|ASSE 1012|X|X|—|—|Installation of potable water connections to
    water boilers. No high-hazard chemicals
    shall be introduced into the system using
    such devices. Designed to operate under con-
    tinuous pressure conditions. May discharge
    water.| |Backflow preventer with
    intermediate atmospheric
    vent and pressure reduc-
    ing valve|ASSE 1081|X|X|—|—|Installation of potable water connections to
    water boilers. No high-hazard chemicals
    shall be introduced into the system using
    such devices. Designed to operate under con-
    tinuous pressure conditions. May discharge
    water.| |Chemical dispenser with
    integral backflow protec-
    tion|ANSI/CAN/
    ASSE/IAPMO
    1055|X|––|X|––|Shall be installed in accordance with
    manufacturer’s installation instructions with
    dedicated water supply whenever possible.| |Dual check backflow
    preventer|ASSE 1024|X|X|—|—|Installation does not include carbonated drink
    dispensers.| |Dual check backflow
    preventer wall hydrants,
    freeze resistant|ASSE 1053|X|––|X|––|Such devices are not for use under
    continuous pressure conditions.4| |Double Check Detector
    Fire Protection Backflow
    Prevention Assembly
    (two independent check
    valves with a parallel
    detector assembly con-
    sisting of a water meter
    and a double check valve
    backflow prevention
    assembly and means for
    field testing)|ASSE 1048|X|X|––|––|Horizontal unless otherwise listed. Access
    and clearance shall be in accordance with the
    manufacturer’s instructions, and not less than
    a 12 inch clearance at the bottom for mainte-
    nance. May need platform/ladder for test and
    repair. Does not discharge water. Installation
    includes a fire protection system and is
    designed to operate under continuous pres-
    sure conditions.|

    142 2025 CALIFORNIA PLUMBING CODE

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    WATER SUPPLY AND DISTRIBUTION

    |TABLE 603.2 BACKFLOW PREVENTION DEVICES, ASSEMBLIES,

  • CRC § 601.3.2 High relevance — show source text

    Table 601.3.2 Minimum Length of Color Field and Size of Letters . . . . . . .138

    601.4 Schools of Cosmetology and Cosmetological Establishments . .138

    601.5 Meat and Poultry Processing Plants . . . . . . . . . . . . . . . . . . . . . .138

    601.6 Collection Centers and

    Facilities . . . . . . . . . . . . . . . . . . . .139

    601.7 Renderers . . . . . . . . . . . . . . . . . . .139

    601.8 Horse Meat and Pet Food

    Establishments . . . . . . . . . . . . . . .139

    602.0 Unlawful Connections . . . . . . . . . .139

    602.1 Prohibited Installation . . . . . . . . . .139

    602.2 Cross-Contamination . . . . . . . . . .139

    602.3 Backflow Prevention . . . . . . . . . . .139

    xxxii 2025 CALIFORNIA PLUMBING CODE

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    TABLE OF CONTENTS

    602.4 Approval by Authority . . . . . . . . . .139

    603.0 Cross-Connection Control . . . . . .139

    603.1 General . . . . . . . . . . . . . . . . . . . . .139

    603.2 Approval of Devices or Assemblies . . . . . . . . . . . . . . . . . .139

    603.3 Backflow Prevention Devices, Assemblies, and Methods . . . . . .140

    603.4 General Requirements . . . . . . . . .140

    603.5 Specific Requirements . . . . . . . . .141

    Table 603.2 Backflow Prevention Devices, Assemblies, and Methods . . . . . .142

    Table 603.3.1 Minimum Air Gaps for Water Distribution . . . . . . . . . . . . . . . . . .144

    604.0 Materials . . . . . . . . . . . . . . . . . . . .146

    604.1 Pipe, Tube, and Fittings . . . . . . . .146

    604.2 Lead Content . . . . . . . . . . . . . . . .147

    604.3 Copper or Copper Alloy Tube . . .147

    604.4 Hard-Drawn Copper or Copper Alloy Tubing . . . . . . . . . . . . . . . . .147

    604.5 Flexible Connectors . . . . . . . . . . .147

    604.6 Cast-Iron Fittings . . . . . . . . . . . . .147

    604.7 Malleable Iron Fittings . . . . . . . . .147

    604.8 Previously Used Piping and Tubing . . . . . . . . . . . . . . . . . . . . . .147

    604.9 Epoxy Coating . . . . . . . . . . . . . . .147

    604.10 Plastic Materials . . . . . . . . . . . . . .147

  • CRC § 603.5.2 High relevance — show source text

    603.5.2 Ballcock. Water closet and urinal tanks shall be equipped with a ballcock. The ballcock shall be installed with the critical level not less than 1 inch (25.4 mm) above the full opening of the overflow pipe. In cases where the ballcock has no hush tube, the bottom of the water supply inlet shall be installed 1 inch (25.4 mm) above the full opening of the overflow pipe.

    603.5.3 Backflow Prevention. Water closet flushometer tanks shall be protected against backflow by an approved backflow prevention assembly, device, or method.

    603.5.4 Heat Exchangers. Heat exchangers used for heat transfer, heat recovery, or solar heating shall protect the potable water system from being contaminated by the

    heat-transfer medium. Single-wall heat exchangers used in indirect-fired water heaters shall meet the requirements of Section 505.4.1. Double-wall heat exchangers shall separate the potable water from the heat-transfer medium by providing a space between the two walls that are vented to the atmosphere. 603.5.5 Water Supply Inlets. Water supply inlets to tanks, vats, sumps, swimming pools, and other receptors shall be protected by one of the following means:

    (1) An approved air gap.

    (2) A listed vacuum breaker installed on the discharge side of the last valve with the critical level not less than 6 inches (152 mm) or in accordance with its listing.

    (3) A backflow preventer suitable for the degree of hazard, installed in accordance with the requirements for that type of device or assembly as set forth in this chapter. 603.5.6 Protection from Lawn Sprinklers and Irri- gation Systems. Potable water supplies to systems having no pumps or connections for pumping equipment, and no chemical injection or provisions for chemical injection, shall be protected from backflow by one of the following devices:

    (1) Atmospheric vacuum breaker (AVB)

    (2) Pressure vacuum breaker backflow prevention assembly (PVB)

    (3) Spill-resistant pressure vacuum breaker (SVB)

    (4) Reduced-pressure principle backflow prevention assembly (RP)

    (5) A valve complying with IAPMO PS 72 603.5.6.1 Systems with Pumps. Where sprinkler and irrigation systems have pumps, connections for pumping equipment, or auxiliary air tanks, or are otherwise capable of creating backpressure, the potable water supply shall be protected by the following type of device where the backflow device is located upstream from the source of backpressure:

    (1) Reduced-pressure principle backflow prevention assembly (RP) 603.5.6.2 Systems with Backflow Devices. Where systems have a backflow device installed downstream from a potable water supply pump or a potable water supply pump connection, the device shall be one of the following:

    (1) Atmospheric vacuum breaker (AVB)

    (2) Pressure vacuum breaker backflow prevention assembly (PVB)

    (3) Spill-resistant pressure vacuum breaker (SVB)

    (4) Reduced-pressure principle backflow prevention assembly (RP) 603.5.6.3 Systems with Chemical Injectors. Where systems include a chemical injector or provisions for chemical injection, the potable water supply shall be protected by a reduced-pressure principle backflow prevention assembly (RP).

    2025 CALIFORNIA PLUMBING CODE 141

  • CRC § 603.3 Medium relevance — show source text

    Testing or maintenance shall be performed by a certified backflow assembly tester or repairer certified in accordance with ASSE/IAPMO/ANSI Series 5000 or any other additional certification approved by the Authority Having Jurisdiction.

    603.3 Backflow Prevention Devices, Assemblies, and Methods. Backflow prevention devices, assemblies, and methods shall comply with Section 603.3.1 through Section 603.3.12.

    603.3.1 Air Gap. The minimum air gap to afford backflow protection shall be in accordance with Table 603.3.1. 603.3.2 Atmospheric Vacuum Breaker (AVB). An atmospheric vacuum breaker consists of a body, a checking member, and an atmospheric port.

    603.3.3 Hose Connection Backflow Preventer. A hose connection backflow preventer consists of two independent check valves with an independent atmospheric vent between and a means of field testing and draining.

    603.3.4 Double Check Valve Backflow Prevention Assembly (DC). A double check valve backflow prevention assembly consists of two independently acting internally loaded check valves, four properly located test cocks, and two isolation valves.

    603.3.5 Pressure Vacuum Breaker Backflow Pre- vention Assembly (PVB). A pressure vacuum breaker backflow prevention assembly consists of a loaded air inlet valve, an internally loaded check valve, two properly located test cocks, and two isolation valves. This device shall be permitted to be installed indoors where provisions for spillage are provided. 603.3.6 Spill-Resistant Pressure Vacuum Breaker (SVB). A pressure-type vacuum breaker backflow prevention assembly consists of one check valve force loaded closed and an air inlet vent valve force loaded open to atmosphere, positioned downstream of the check valve and located between and including two tightly closing shutoff valves and test cocks. 603.3.7 Reduced-Pressure Principle Backflow Prevention Assembly (RP). A reduced-pressure principle backflow prevention assembly consists of two independently acting internally loaded check valves, a differential pressure relief valve, four properly located test cocks, and two isolation valves.

    603.3.8 Double Check Detector Fire Protection Backflow Prevention Assembly. A double check valve backflow prevention assembly with a parallel

    detector assembly consisting of a water meter and a double check valve backflow prevention assembly (DC).

    603.3.9 Reduced Pressure Detector Fire Protec- tion Backflow Prevention Assembly. A reducedpressure principle backflow prevention assembly with a parallel detector assembly consisting of a water meter and a reduced-pressure principle backflow prevention assembly (RP).

    603.3.10 Dual Check Backflow Preventer. A dual check backflow preventer consists of two independently acting check valves, force loaded to a normally closed position.

    603.3.11 Laboratory Faucet Backflow Preven- ters. Laboratory faucet backflow preventers shall comply with ASSE 1035.

    603.3.12 Backflow Preventer with Intermediate Atmospheric Vent. A backflow preventer with intermediate atmospheric vent consists of two independently acting check valves, force loaded to a normally closed position, and an intermediate chamber with a means for automatically venting to atmosphere, force loaded to a normally open position. 603.4 General Requirements. Assemblies shall comply with listed standards and be acceptable to the Authority Having Jurisdiction, with jurisdiction over the selection and installation of backflow prevention assemblies.

    **603.4.1 Backflow Prevention Valve.

  • CRC § 603.5.6.1 Medium relevance — show source text

    (1) Atmospheric vacuum breaker (AVB)

    (2) Pressure vacuum breaker backflow prevention assembly (PVB)

    (3) Spill-resistant pressure vacuum breaker (SVB)

    (4) Reduced-pressure principle backflow prevention assembly (RP)

    (5) A valve complying with IAPMO PS 72 603.5.6.1 Systems with Pumps. Where sprinkler and irrigation systems have pumps, connections for pumping equipment, or auxiliary air tanks, or are otherwise capable of creating backpressure, the potable water supply shall be protected by the following type of device where the backflow device is located upstream from the source of backpressure:

    (1) Reduced-pressure principle backflow prevention assembly (RP) 603.5.6.2 Systems with Backflow Devices. Where systems have a backflow device installed downstream from a potable water supply pump or a potable water supply pump connection, the device shall be one of the following:

    (1) Atmospheric vacuum breaker (AVB)

    (2) Pressure vacuum breaker backflow prevention assembly (PVB)

    (3) Spill-resistant pressure vacuum breaker (SVB)

    (4) Reduced-pressure principle backflow prevention assembly (RP) 603.5.6.3 Systems with Chemical Injectors. Where systems include a chemical injector or provisions for chemical injection, the potable water supply shall be protected by a reduced-pressure principle backflow prevention assembly (RP).

    2025 CALIFORNIA PLUMBING CODE 141

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

    WATER SUPPLY AND DISTRIBUTION

    TABLE 603.2 BACKFLOW PREVENTION DEVICES, ASSEMBLIES, AND METHODS Col2 Col3 Col4 Col5 Col6 Col7
    DEGREE OF HAZARD DEGREE OF HAZARD DEGREE OF HAZARD DEGREE OF HAZARD DEGREE OF HAZARD DEGREE OF HAZARD DEGREE OF HAZARD
    DEVICE, ASSEMBLY,
    OR METHOD1    		 APPLICABLE
    STANDARDS    		 POLLUTION
    (LOW HAZARD)    		 POLLUTION
    (LOW HAZARD)    		 CONTAMINATION
    (HIGH HAZARD)    		 CONTAMINATION
    (HIGH HAZARD)    		 INSTALLATION2,3
    DEVICE, ASSEMBLY,
    OR METHOD1    		 APPLICABLE
    STANDARDS    		 BACK-
    SIPHONAGE    		 BACK-
    PRESSURE    		 BACK-
    SIPHONAGE    		 BACK-
    PRESSURE    		 BACK-
    PRESSURE
    Air gap ASME
    A112.1.2    		 X –– X –– See Table 603.3.1 in this chapter.
    Air gap fittings for use
    with plumbing fixtures,
    appliances, and appurte-
    nances    		 ASME
    A112.1.3    		 X –– X –– Air gap fitting is a device with an internal air
    gap, and typical installation includes
    plumbing fixtures, appliances,
  • CRC § 1505.14.2.2 Medium relevance — show source text

    **_ A visual dual system inspection shall be conducted by the Authority Having Jurisdiction and other authorities having jurisdiction to verify that no modifications were made, and that no cross-connections are visi- ble as follows:

    (1) Meter locations of the reclaimed (recycled) water source and potable water lines shall be checked.

    (2) All pumps and equipment, equipment room signs, and exposed piping in equipment room shall be checked.

    (3) All valves shall be checked to ensure that the valve lock seals are still in place and intact. Valve control door signs shall be checked to verify that no signs have been removed.

    1505.14.2.2 Cross-Connection Test. A cross- connection test shall be performed pursuant to Sec- tion 1505.14.2. The test shall be conducted in the presence of the Authority Having Jurisdiction or other authorities having jurisdiction to determine whether a cross connection has occurred as follows:

    (1) The potable water system shall be activated and pressurized. The recycled water supply system shall be shut down, depressurized, and drained.

    (2) The potable water system shall remain pressur- ized for a minimum period of time specified by the Authority Having Jurisdiction while the recycled water supply system is empty. The min- imum period the recycled water supply system is to remain depressurized shall be determined on a case-by-case basis, taking into account the size and complexity of the potable and the recy- cled water supply systems, but in no case shall that period be less than 1 hour.

    (3) All fixtures, potable and reclaimed (recycled) water source, shall be tested and inspected for flow. Flow from a recycled water supply system outlet indicates a cross-connection. No flow from a potable water outlet shall indicate that it is connected to the recycled water supply system.

    (4) The drain on the recycled water supply system shall be checked for flow during the test and at the end of the test.

    (5) The potable water system shall then be depres- surized and drained.

    (6) The recycled water supply system shall then be activated and pressurized. For the initial cross- connection test, a temporary connection to a potable water supply shall be required to test the recycled water supply system plumbing. At the conclusion of the initial cross-connection test, the temporary connection to the potable water supply shall be disconnected.

    (7) The recycled water supply system shall remain pressurized for a minimum period of time spec- ified by the Authority Having Jurisdiction while the potable water system is empty. The mini- mum period the potable water system is to remain depressurized shall be determined on a case-by-case basis, but in no case shall that period be less than 1 hour.

    (8) All fixtures, potable and reclaimed (recycled) water, shall be tested and inspected for flow. Flow from a potable water system outlet indi- cates a cross-connection. No flow from a recy- cled water supply system outlet will indicate that it is connected to the potable water system.

    (9) The drain on the potable water system shall be checked for flow during the test and at the end of the test.

    (10)Where there is no flow detected in the fixtures that would indicate a cross-connection, the potable water system shall be repressurized.

  • CRC § 603.5.9 Medium relevance — show source text

    603.5.9 Aspirators. Water inlets to water-supplied aspirators shall be equipped with a vacuum breaker installed in accordance with its listing requirements and this chapter. The discharge shall drain through an air gap. Where the tailpiece of a fixture to receive the discharge of an aspirator is used, the air gap shall be located above the flood-level rim of the fixture.

    603.5.10 Steam or Hot Water Boilers. Potable water connections to steam or hot water boilers shall be protected from backflow by a double check valve backflow prevention assembly, backflow preventer with intermediate atmospheric vent and pressure reducing valve, or reduced pressure principle backflow prevention assembly in accordance with Table 603.2. Where chemicals are introduced into the system a reduced pressure principle backflow prevention assembly shall be provided in accordance with Table 603.2.

    603.5.11 Nonpotable Water Piping. In cases where it is impractical to correct individual cross-connections on the domestic waterline, the line supplying such outlets

    shall be considered a nonpotable water line. No drinking or domestic water outlets shall be connected to the nonpotable waterline. Where possible, portions of the nonpotable waterline shall be exposed, and exposed portions shall be properly identified in a manner satisfactory to the Authority Having Jurisdiction. Each outlet on the nonpotable waterline that is permitted to be used for drinking or domestic purposes shall be posted: “CAUTION: NONPOTABLE WATER, DO NOT DRINK.”

    [HCD 1 & HCD 2] An international symbol of a glass in a circle with a slash through it shall be provided sim- ilar to that shown in Figure 601.

    603.5.12 Beverage Dispensers. Potable water supply to carbonated beverage dispensers shall be protected by an air gap or a vented backflow preventer that complies with ASSE 1022. For carbonated beverage dispensers, piping material installed downstream of the backflow preventer shall not be affected by carbon dioxide gas. Non-carbonated beverage dispensers, such as ice makers and coffee machines, shall be protected by an air gap or dual check backflow preventer that comply with ASSE 1032 or ASSE 1024.

    603.5.13 Deck-Mounted and Equipment- Mounted Vacuum Breakers. Deck-mounted or equipment-mounted vacuum breakers shall be installed in accordance with their listing and the manufacturer’s installation instructions, with the critical level not less than 1 inch (25.4 mm) above the flood-level rim.

    603.5.14 Protection from Fire Systems.

    Note: Fire Protection Systems has not been adopted by the State Fire Marshal. This section cannot be adopted or enforced pursuant to California Health and Safety Code 13114.7(a), which is being cited for reference. California Health and Safety Code 13114.7.

    (a) For the purposes of this section the following are definitions of class I and class II systems:

    144 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

  • CRC § 25.4 Medium relevance — show source text

    2 Vertical walls, ribs, or similar obstructions extending from the water surface to or above the horizontal plane of the spout opening other than specified in Footnote 1 above. The effect of three or more such vertical walls or ribs has not been determined. In such cases, the air gap shall be measured from the top of the wall. 3 The effective opening shall be the minimum cross-sectional area at the seat of the control valve or the supply pipe or tubing that feeds the device or outlet. Where two or more lines supply one outlet, the effective opening shall be the sum of the cross-sectional areas of the individual supply lines or the area of the single outlet, whichever is smaller. 4 Air gaps less than 1 inch (25.4 mm) shall be approved as a permanent part of a listed assembly that has been tested under actual backflow conditions with vacuums of 0 to 25 inches of mercury (85 kPa).

    603.5.7 Outlets with Hose Attachments. Potable water outlets with hose attachments, other than water heater drains, boiler drains, and clothes washer connections, shall be protected by a nonremovable hose bibbtype backflow preventer, a nonremovable hose bibb-type vacuum breaker, or by an atmospheric vacuum breaker installed not less than 6 inches (152 mm) above the highest point of usage located on the discharge side of the last valve. In climates where freezing temperatures occur, a listed self-draining frost-proof hose bibb with an integral backflow preventer or vacuum breaker shall be used. 603.5.8 Water-Cooled Equipment. Water-cooled compressors, degreasers, or other water-cooled equipment shall be protected by a backflow preventer installed in accordance with the requirements of this chapter. Water-cooled equipment that produces backpressure shall be equipped with the appropriate protection. 603.5.9 Aspirators. Water inlets to water-supplied aspirators shall be equipped with a vacuum breaker installed in accordance with its listing requirements and this chapter. The discharge shall drain through an air gap. Where the tailpiece of a fixture to receive the discharge of an aspirator is used, the air gap shall be located above the flood-level rim of the fixture.

    603.5.10 Steam or Hot Water Boilers. Potable water connections to steam or hot water boilers shall be protected from backflow by a double check valve backflow prevention assembly, backflow preventer with intermediate atmospheric vent and pressure reducing valve, or reduced pressure principle backflow prevention assembly in accordance with Table 603.2. Where chemicals are introduced into the system a reduced pressure principle backflow prevention assembly shall be provided in accordance with Table 603.2.

    603.5.11 Nonpotable Water Piping. In cases where it is impractical to correct individual cross-connections on the domestic waterline, the line supplying such outlets

    shall be considered a nonpotable water line. No drinking or domestic water outlets shall be connected to the nonpotable waterline. Where possible, portions of the nonpotable waterline shall be exposed, and exposed portions shall be properly identified in a manner satisfactory to the Authority Having Jurisdiction. Each outlet on the nonpotable waterline that is permitted to be used for drinking or domestic purposes shall be posted: “CAUTION: NONPOTABLE WATER, DO NOT DRINK.”

    [HCD 1 & HCD 2] An international symbol of a glass in a circle with a slash through it shall be provided sim- ilar to that shown in Figure 601.

  • CRC § 4.33 Medium relevance — show source text

    [RB] APPROVED AGENCY. An established and recognized organization that is regularly engaged in conducting tests, furnishing inspection services or furnishing product evaluation or certification where such organization has been approved. (HCD 1) “Approved agency” shall mean “Listing agency” and “Testing agency.”

    APPROVED LISTING AGENCY. Any agency approved by the enforcing agency, unless otherwise provided by statute, which is in the busi- ness of listing and labeling and which makes available at least an annual published report of such listings in which specific information is included that the product has been tested to recognized standards and found to comply.

    [RB] APPROVED SOURCE. An independent person, firm or corporation, approved by the building official, who is competent and experienced in the application of engineering principles to materials, methods or systems analyses.

    APPROVED TESTING AGENCY. Any agency which is determined by the enforcing agency, except as otherwise provided by statute, to have adequate personnel and expertise to carry out the testing of systems, materials and construction fixtures or appliances.

    [RB] ASPECT RATIO. The ratio of longest to shortest perpendicular dimensions, or for wall sections, the ratio of height to length.

    [RB] ATTIC. The unfinished space between the ceiling assembly and the roof assembly.

    [RB] ATTIC, HABITABLE. A finished or unfinished habitable space within an attic.

    [MP] BACKFLOW, DRAINAGE. A reversal of flow in the drainage system.

    [MP] BACKFLOW, WATER DISTRIBUTION. The flow of water or other liquids into the potable water-supply piping from any sources other than its intended source. Backsiphonage is one type of backflow.

    [MP] BACKFLOW PREVENTER. A backflow prevention assembly, a backflow prevention device or other means or method to prevent backflow into the potable water supply.

    [MP] BACKFLOW PREVENTER, REDUCED-PRESSURE-ZONE TYPE. A backflow-prevention device consisting of two independently acting check valves, internally force loaded to a normally closed position and separated by an intermediate chamber (or zone) in which there is an automatic relief means of venting to atmosphere internally loaded to a normally open position between two tightly closing shutoff valves and with means for testing for tightness of the checks and opening of relief means.

    [MP] BACKPRESSURE. Pressure created by any means in the water distribution system that by being in excess of the pressure in the water supply mains causes a potential backflow condition.

    [MP] BACKPRESSURE, LOW HEAD. A pressure less than or equal to 4.33 psi (29.88 kPa) or the pressure exerted by a 10-foot (3048 mm) column of water.

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

    DEFINITIONS

    [MP] BACKSIPHONAGE. The flowing back of used or contaminated water from piping into a potable water-supply pipe due to a negative pressure in such pipe.

    [MP] BACKWATER VALVE. A device installed in a drain or pipe to prevent backflow of sewage.

  • CRC § 603.2 Medium relevance — show source text

    3, Table 603.2| |ASSE 1003-2020e2|Water Pressure Reducing Valves for Potable Water Distribution
    Systems|Valves|608.2| |ASSE 1004-2017|Commercial Dishwashing Machines|Backflow Protection|414.2| |ASSE 1008-2020|Plumbing Aspects of Residential Food Waste Disposer Units|Appliances|419.1| |ASSE 1010-2004|Water Hammer Arresters|Appliances|609.11| |ASSE 1011-2017|Hose Connection Vacuum Breakers|Backflow Protection|Table 603.2|

    2025 CALIFORNIA PLUMBING CODE 337

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

    REFERENCED STANDARDS

    TABLE 1701.1 (continued) REFERENCED STANDARDS

    STANDARD NUMBER STANDARD TITLE APPLICATION REFERENCED
    SECTION
    ASSE 1012-2009 Backflow Preventers with an Intermediate Atmospheric Vent Backflow Protection Table 603.2
    ASSE 1013-2021 Reduced Pressure Principle Backflow Prevention Assemblies Backflow Protection Table 603.2
    ASSE 1014-2020 Backflow Prevention Devices for Hand-Held Showers Backflow Protection 417.3
    ASSE 1015-2021 Double Check Backflow Prevention Backflow Protection Table 603.2
    ASSE 1016-2017/ASME
    A112.1016-2017/CSA
    B125.16-2017    		 Automatic Compensating Valves for Individual Showers and
    Tub/Shower Combinations    		 Valves 408.4, 408.4.2(1)
    ASSE 1018-2001 (R2021) Trap Seal Primer Valves - Potable Water Supplied Valves 1007.2
    ASSE 1019-2011 (R2016) Wall Hydrant with Backflow Protection and Freeze Resistance Backflow Protection Table 603.2
    ASSE 1020-2020 Pressure Vacuum Breaker Assemblies Backflow Protection Table 603.2
    ASSE 1022-2021 Backflow Preventer for Beverage Dispensing Equipment Backflow Protection Table 603.2,
    603.5.12
    ASSE 1023-2020 Electrically Heated or Cooled Water Dispensers Appliances 417.6
    ASSE 1024-2017 (R2021) Dual Check Backflow Preventers Backflow Protection Table 603.2, 603.5.12
    ASSE 1032-2004 (R2021) Dual Check Valve Type Backflow Preventers for Carbonated
    Beverage Dispensers, Post Mix Type    		 Backflow Protection 603.5.12
    ASSE 1035-2020 Laboratory Faucet Backflow Preventers Backflow Protection Table 603.2,
    603.3.11
    ASSE 1037-2020/ASME
    A112.1037-2020/CSA
    B125.37-2020    		 Pressurized Flushing Devices for Plumbing Fixtures Backflow Protection 413.2
    ASSE 1044-2015 (R2020) Trap Seal Primer - Drainage Types and Electric Design Types DWV Components 1007.
  • CRC § 3.5.3 Medium relevance — show source text

    2.4. A sign shall be provided stating “Valve must be opened monthly for 5 minutes.” 2.5. A means for automatically refilling the tank level so that the tank capacity will meet the required water supply duration in minutes shall be provided.

    R309.3.5.3 Connections to automatic fire sprinkler systems. The potable water supply to automatic fire sprinkler shall be protected against backflow by a double check backflow prevention assembly, a double check fire protection backflow prevention assembly, a reduced pressure principle backflow prevention assembly or a reduced pressure principle fire protection backflow prevention assembly.

    Exception: Where permitted by Section R309.3.1.1, backflow protection for the water supply system shall not be required.

    R309.3.5.3.1 Additives or nonpotable source. Where systems contain chemical additives or antifreeze, or where systems are connected to a nonpotable secondary water supply, the potable water supply shall be protected against backflow by a reduced pressure principle backflow prevention assembly or a reduced pressure principle fire protection backflow prevention assembly. Where chemical additives or antifreeze is added to only a portion of an automatic sprinkler or standpipe system, the reduced pressure principle fire protection backflow preventer shall be permitted to be located so as to isolate that portion of the system.

    R309.3.6 Pipe sizing. The piping to sprinklers shall be sized for the flow required by Section R309.3.4.2. The flow required to supply the plumbing fixtures shall not be required to be added to the sprinkler design flow.

    R309.3.6.1 Method of sizing pipe. Piping supplying sprinklers shall be sized using the prescriptive method in Section R309.3.6.2 or by hydraulic calculation in accordance with NFPA 13D. The minimum pipe size from the water supply source to any sprinkler shall be [3] / 4 inch (19 mm) nominal. Threaded adapter fittings at the point where sprinklers are attached to the piping shall be not less than [1] / 2 inch (13 mm) nominal.

    R309.3.6.2 Prescriptive pipe sizing method. Pipe shall be sized by determining the available pressure to offset friction loss in piping and identifying a piping material, diameter and length using the equation in Section R309.3.6.2.1 and the procedure in Section R309.3.6.2.2 .

    2025 CALIFORNIA RESIDENTIAL CODE 3-45

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

    BUILDING PLANNING

    TABLE R309.3.6.2(1)—WATER SERVICE PRESSURE LOSS (PL ) a, b
    svc    		 Col2 Col3 Col4 Col5 Col6 Col7 Col8 Col9 Col10 Col11 Col12 Col13
    FLOW
    RATEc
    (gpm)    		 3/4-INCH WATER SERVICE
    PRESSURE LOSS (psi)    		 3/4-INCH WATER SERVICE
    PRESSURE LOSS (psi)    		 3/4-INCH WATER SERVICE
    PRESSURE LOSS (psi)    		 **3/4-INCH
  • CRC § 3-2020 Medium relevance — show source text

    3-2020|Process Piping|Piping|1308.2(9)| |ASME B36.10M-2018|Welded and Seamless Wrought Steel Pipe|Fuel Gas, Piping|1208.5.2.2| |ASME BPVC Section
    VIII.1-2021|Rules for Construction of Pressure Vessels - Division 1|Miscellaneous|505.4, 1309.5(2),
    1310.4(2), 1312.3(2)| |ASME BPVC Section IX-
    2021|Welding, Brazing, and Fusing Qualifications - Qualification
    Standard for Welding, Brazing, and Fusing Procedures;
    Welders; Brazers; and Welding, Brazing, and Fusing Operators|Miscellaneous|1322.1.1, 1322.2.1,
    1323.11| |ASPE|ASPE|ASPE|ASPE| |ASPE/ANSI 45-2018|Siphonic Roof Drainage|Storm Drainage|1106.2| |ARCSA/ASPE/ANSI 63-
    2020|Rainwater Catchment Systems|Miscellaneous|1602.1| |ASSE|ASSE|ASSE|ASSE| |ASSE 1001-2017|Atmospheric Type Vacuum Breakers|Backflow Protection|Table 603.2| |ASSE 1002-2020/ASME
    A112.1002-2020/CSA
    B125.12-2020|Anti-Siphon Fill Valves for Water Closet Tanks|Backflow Protection|413.3, Table 603.2| |ASSE 1003-2020e2|Water Pressure Reducing Valves for Potable Water Distribution
    Systems|Valves|608.2| |ASSE 1004-2017|Commercial Dishwashing Machines|Backflow Protection|414.2| |ASSE 1008-2020|Plumbing Aspects of Residential Food Waste Disposer Units|Appliances|419.1| |ASSE 1010-2004|Water Hammer Arresters|Appliances|609.11| |ASSE 1011-2017|Hose Connection Vacuum Breakers|Backflow Protection|Table 603.2|

    2025 CALIFORNIA PLUMBING CODE 337

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

    REFERENCED STANDARDS

    TABLE 1701.1 (continued) REFERENCED STANDARDS

    STANDARD NUMBER STANDARD TITLE APPLICATION REFERENCED
    SECTION
    ASSE 1012-2009 Backflow Preventers with an Intermediate Atmospheric Vent Backflow Protection Table 603.2
    ASSE 1013-2021 Reduced Pressure Principle Backflow Prevention Assemblies Backflow Protection Table 603.2
    ASSE 1014-2020 Backflow Prevention Devices for Hand-Held Showers Backflow Protection 417.3
    ASSE 1015-2021 Double Check Backflow Prevention Backflow Protection Table 603.2
    ASSE 1016-2017/ASME
    A112.1016-2017/CSA
    B125.
  • CRC § 420.1 Medium relevance — show source text

    420.1| |CSA B45.8-2018/IAPMO
    Z403-2018|Terrazzo, Concrete, Composite Stone, and Natural Stone
    Plumbing Fixtures|Fixtures|407.1, 420.1| |ASME A112.3.4-2018/CSA
    B45.9-2018|Macerating Toilet Systems and Waste-Pumping Systems for
    Plumbing Fixtures|Fixtures|710.13| |ASME A112.19.7-
    2020/CSA B45.10-2020|Hydromassage Bathtub Systems|Fixtures|409.1, 409.6.1|

    2025 CALIFORNIA PLUMBING CODE 345

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

    REFERENCED STANDARDS

    TABLE 1701.1 (continued) REFERENCED STANDARDS

    STANDARD NUMBER STANDARD TITLE APPLICATION REFERENCED
    SECTION
    CSA B45.11-2017/IAPMO
    Z401-2017 (R2021)    		 Glass Plumbing Fixtures Fixtures 407.1
    CSA B45.12-2013/IAPMO
    Z402-2013 (R2018)    		 Aluminum and Copper Plumbing Fixtures Fixtures 407.1, 408.1, 409.1,
    420.1
    ASME A112.19.5-
    2017/CSA B45.15-2017    		 Flush Valves and Spuds for Water Closets, Urinals, and Tanks Fixtures 413.3
    ASME A112.4.2-2021/CSA
    B45.16-2021    		 Personal Hygiene Devices for Water Closets Fixtures 411.4
    CSA B64.1.1-2021 Atmospheric Vacuum Breakers (AVB) Backflow Protection Table 603.2
    CSA B64.1.2-2021 Pressure Vacuum Breakers (PVB) Backflow Protection Table 603.2
    CSA B64.2.1.1-2021 Hose Connection Dual Check Vacuum Breakers (HCDVB) Backflow Protection Table 603.2
    CSA B64.4-2021 Reduced Pressure Principle (RP) Backflow Preventers Backflow Protection Table 603.2
    CSA B64.4.1-2021 Reduced Pressure Principle Backflow Preventers for Fire Pro-
    tection Systems (RPF)    		 Backflow Protection Table 603.2
    CSA B64.5-2021 Double Check Valve (DCVA) Backflow Preventers Backflow Protection Table 603.2
    CSA B64.5.1-2021 Double Check Valve Backflow Preventers for Fire Protection
    Systems (DCVAF)    		 Backflow Protection Table 603.2
    CSA B79-2008 (R2018) Commercial and Residential Drains and Cleanouts Fixtures 418.1, Table 707.2
    ASME A112.18.1-
    2018/CSA B125.1-2018    		 Plumbing Supply Fittings Fittings 408.4, 417.1, 417.2,
    417.3, 417.4, 417.6,
    603.5.20
    ASME A112.18.
  • CRC § 1.8.2.1.1. Medium relevance — show source text

    [MP] ANCHORS. See “Supports.”

    [MP] ANTISIPHON. A term applied to valves or mechanical devices that eliminate siphonage.

    [MP] APPLIANCE. A device or apparatus that is manufactured and designed to utilize energy and for which this code provides specific requirements.

    [RB] APPROVED. Acceptable to the building official.

    APPROVED. (HCD 1) Meeting the approval of the enforcing agency, except as otherwise provided by law, when used in connection with any system, material, type of construction, fixture or appliance as the result of investigations and tests conducted by the agency, or by reason of accepted principles or tests by national authorities or technical, health or scientific organizations or agencies.

    Notes:

    1. See Health and Safety Code Section 17920 for “Approved” as applied to residential construction and buildings or structures accessory thereto, as referenced in Section 1.8.2.1.1. 2. See Health and Safety Code Section 17921.1 for “Approved” as applied to the use of hotplates in residential construction referenced in Section 1.8.2.1.1.

    3. See Health and Safety Code Section 19966 for “Approved” as applied to factory-built housing as referenced in Section 1.8.3.2.5.

    4. See Health and Safety Code Section 18201 for “Approved” as applied to mobilehome parks as referenced in Section 1.8.3.2.2. 5. See Health and Safety Code Section 18862.1 for “Approved” as applied to special occupancy parks as referenced in Section 1.8.3.2.3.

    [RB] APPROVED AGENCY. An established and recognized organization that is regularly engaged in conducting tests, furnishing inspection services or furnishing product evaluation or certification where such organization has been approved. (HCD 1) “Approved agency” shall mean “Listing agency” and “Testing agency.”

    APPROVED LISTING AGENCY. Any agency approved by the enforcing agency, unless otherwise provided by statute, which is in the busi- ness of listing and labeling and which makes available at least an annual published report of such listings in which specific information is included that the product has been tested to recognized standards and found to comply.

    [RB] APPROVED SOURCE. An independent person, firm or corporation, approved by the building official, who is competent and experienced in the application of engineering principles to materials, methods or systems analyses.

    APPROVED TESTING AGENCY. Any agency which is determined by the enforcing agency, except as otherwise provided by statute, to have adequate personnel and expertise to carry out the testing of systems, materials and construction fixtures or appliances.

    [RB] ASPECT RATIO. The ratio of longest to shortest perpendicular dimensions, or for wall sections, the ratio of height to length.

    [RB] ATTIC. The unfinished space between the ceiling assembly and the roof assembly.

    [RB] ATTIC, HABITABLE. A finished or unfinished habitable space within an attic.

    [MP] BACKFLOW, DRAINAGE. A reversal of flow in the drainage system.

    [MP] BACKFLOW, WATER DISTRIBUTION. The flow of water or other liquids into the potable water-supply piping from any sources other than its intended source. Backsiphonage is one type of backflow.

  • CRC § 12-0 Medium relevance — show source text

    000|DR|DR|12-0|15-3|10-11|15-0|10-2|14-8| |8|2-#4
    1-#6|60,000|DR|DR|DR|DR|12-2|15-3|11-7|15-3| |8|2-#5|40,000|DR|DR|DR|DR|12-7|16-7|11-9|16-7| |8|2-#5|60,000|DR|DR|DR|DR|DR|DR|13-3|16-7| |8|2-#6|40,000|DR|DR|DR|DR|DR|DR|13-2|17-8| |8|2-#6|60,000|DR|DR|DR|DR|DR|DR|DR|DR| |12|1-#4|40,000|11-5|9-10|10-6|12-0|9-6|11-6|8-9|11-1| |12|1-#4|60,000|11-5|9-10|11-8|13-3|10-11|14-0|10-1|13-6| |12|1-#5|40,000|11-5|9-10|11-8|13-3|11-1|14-4|10-3|13-9| |12|1-#5|60,000|11-5|9-10|11-8|13-3|11-10|16-0|11-9|16-9| |12|2-#4
    1-#6|40,000|DR|DR|11-8|13-3|11-10|16-0|11-2|15-6| |12|2-#4
    1-#6|60,000|DR|DR|11-8|13-3|11-10|16-0|11-11|18-4| |12|2-#5|40,000|DR|DR|11-8|13-3|11-10|16-0|11-11|18-4| |12|2-#5|60,000|DR|DR|11-8|13-3|11-10|16-0|11-11|18-4| |16|1-#4|40,000|13-6|13-0|11-10|13-8|10-7|12-11|9-11|12-4| |16|1-#4|60,000|13-6|13-0|13-8|16-7|12-4|15-9|11-5|15-0| |16|1-#5|40,000|13-6|13-0|13-10|17-0|12-6|16-1|11-7|15-4| |16|1-#5|60,000|13-6|13-0|13-10|17-1|14-0|19-7|13-4|18-8| |16|2-#4
    1-#6|40,000|13-6|13-0|13-10|17-1|13-8|18-2|12-8|17-4| |16|2-#4
    1-#6|60,

  • CRC § 17062.5 Medium relevance — show source text

    References – Health and Safety Code Sections 17000 through 17062.5, 17910 through 17995.5, 18200 through 18700, 18860 through 18874, 18938.6, 18941, 18941.5, 19890, 19891, 19892 and 19960 through 19997; Civil Code Sections 1101.4, 1101.5, 1954.201, 1954.202 and 5551; and Government Code Sections 8698.4, 12955.1, 12955.1.1 and 65852.2. California Code of Regulations, Title 20, Sections 1605.1, 1605.3 and 1607.

    12 2025 CALIFORNIA PLUMBING CODE

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

    DIVISION I CALIFORNIA ADMINISTRATION

    1.9.0 Division of the State Architect.

    1.9.1 Division of the State Architect – Access Compliance. Note: Buildings or facilities where accessibility is required for applications listed in California Code of Regulations, Title 24, Part 2 (California Building Code), Chapter 1, Section 1.9.1 regulated by the Division of the State Architect–Access Compliance shall comply with Title 24, Part 2, Chapter 11A or 11B, as applicable under authority cited by CA Govern- ment Code Section 4450 and in reference cited by CA Gov- ernment Code Sections 4450 through 4461, 12955.1(c), and CA Health and Safety Code Sections 18949.1, 19952 through 19959.

    1.9.1.1 Adopting Agency Identification. The provisions of this code applicable to buildings identified in this Sub- section 1.9.1 will be identified in the Matrix Adoption Tables under the acronym DSA-AC.

    1.9.2 Division of the State Architect – Structural Safety.

    1.9.2.1 DSA-SS (Division of the State Architect – Struc- tural Safety).

    Application – Public elementary and secondary schools, community college buildings, and state-owned or state- leased essential services buildings.

    Enforcing Agency – Division of the State Architect – Structural Safety (DSA-SS).

    The Division of the State Architect has been dele- gated the responsibility and authority by the Department of General Services to review and approve the design and oversee and observe the construction of public elemen- tary and secondary schools, community colleges, and state-owned or state-leased essential services buildings.

    Authority Cited – Education Code Section 17310 and 81142, and Health and Safety Code Section 16022.

    References – Education Code Sections 17280 through 17317 and 81130 through 81147, and Health and Safety Code Sections 16000 through 16023.

    1.9.2.1.1 Adopting Agency Identification. The pro- visions of this code applicable to buildings identi- fied in this Subsection 1.9.2.1 will be identified in the Matrix Adoption Tables under the acronym DSA- SS.

  • CRC § 0.30 Medium relevance — show source text

    1. Guards per Section 1013 if a rooftop platform is provided; or

    2. A railing that is 12 inches (305 mm) in height if a sloped roof is provided.

    K107.6 Utility/equipment buffer zone. A separation of 48 inches shall be provided between a rooftop evacuation location and any mechanical equipment, photovoltaic system, utility service drop or other utility line. Electrical service lines shall not pass over evacua- tion locations.

    SECTION K108 — ATTICS THAT ARE EVACUATION LOCATIONS

    K108.1 General. Attics that have finish floors no less than one (1) foot (0.30 meter) above the WSEL200 shall be permitted to be evacua- tion locations.

    K108.2 Headroom. When an attic is used as an evacuation location, the minimum headroom of the required area shall be 30 inches (762 mm) with 50 percent of the required area having a headroom of 60 inches (1524 mm).

    K108.3 Attic flooring. The required area of the evacuation location shall be solidly sheathed.

    K108.4 Attic live loads. Attic areas that are used as evacuation locations shall be designed for the floor live load required for the occu- pancy as required in Table 1607.2.

    K108.5 Evacuation routes to attic evacuation locations. Evacuation routes to attic evacuation locations shall be permitted to be provided by a stairway, ramp, alternating tread device, fixed ladder or other means approved by the building official.

    Exception: In Group R-3.1 occupancies that are subject to the requirements of Chapter 11A or 11B, such requirements shall apply to the evacuation routes to attics.

    K108.6 Means of escape from attics. The means of escape from attics shall comply with Section K105.

    SECTION K109 — ALTERNATE MEANS OF PROTECTION

    K109.1 Request for approval of alternate means of protection. Requests for approval to use an alternative means of protection shall be made in writing to the building official by the owner or the owner’s authorized representative. The request shall be accompanied by a full statement of the conditions and sufficient evidence that the proposed alternate means of protection provides reasonable protection to occupants. The building official shall require the owner to obtain a written statement from the applicable emergency management authority regarding plans and processes related to notification of anticipated conditions of flooding, warnings, evacuations and other pertinent conditions relative to the proximity of nearby levees. The building official shall also require the owner to obtain a written state- ment and findings from the entity that has jurisdiction over the management, maintenance, monitoring and control of flood protection works in the vicinity of the location of the owner’s property; such statement shall comment on the viability of the proposed alternate means of protection. The building official may request written statements from the Central Valley Flood Protection Board, the California Department of Water Resources, and the California Emergency Management Agency.

    Approval of a request for use of an alternative means of protection made pursuant to these provisions shall be limited to the particu- lar case covered by the request and shall not be construed as establishing any precedent for any future request except in substantially equivalent situations.

  • CRC § 0.25 Medium relevance — show source text

    WHEN**
    THE MAXIMUM
    ALLOWABLE
    QUANTITY IS
    EXCEEDED|STORAGEb|STORAGEb|STORAGEb|USE-CLOSED SYSTEMSb|USE-CLOSED SYSTEMSb|USE-CLOSED SYSTEMSb|USE-OPEN SYSTEMSb|USE-OPEN SYSTEMSb| |MATERIAL|CLASS|GROUP WHEN
    THE MAXIMUM
    ALLOWABLE
    QUANTITY IS
    EXCEEDED|Solid
    pounds
    (cubic feet)|Liquid
    gallons
    (pounds)|Gas
    (cubic feet
    at NTP)|Solid
    pounds
    (cubic feet)|Liquid
    gallons
    (pounds)|Gas
    (cubic
    feet at
    NTP)|Solid
    pounds
    (cubic
    feet)|Liquid
    gallons
    (pounds)| |Flammable
    liquidn|IA
    IB and IC|H-2
    or
    H-3|NA|30d, e|NA|NA|30d|NA|NA|10d| |Flammable
    liquidn|IA
    IB and IC|H-2
    or
    H-3|NA|120d, e|120d, e|120d, e|120d|120d|120d|30d| |Flammable
    liquid,
    combination
    (IA, IB, IC)n|NA|H-2
    or
    H-3|NA|120d, e, h|NA|NA|120d, h|NA|NA|30d, h| |Flammable
    solid|NA|H-3|125d, e|NA|NA|125d|NA|NA|25d|NA| |Inert gas|Gaseous|NA|NA|NA|NL|NA|NA|NL|NA|NA| |Inert gas|Liquefied|NA|NA|NA|NL|NA|NA|NL|NA|NA| |Organic
    peroxide|UD|H-1|1e, g|(1)e, g|NA|0.25g|(0.25)g|NA|0.25g|(0.25)g| |Organic
    peroxide|I|H-2|5d, e|(5)d, e|(5)d, e|1d|(1)d|(1)d|1d|(1)d| |Organic
    peroxide|II|H-3|50d, e|(50)d, e|(50)d, e|50d|(50)d|(50)d|10d|(10)d| |Organic
    peroxide|III|H-3|125d, e|(125)d, e|(125)d,

Frequently asked questions

What is the single easiest compliant solution for a small garden cistern fill inlet?

Use an approved air gap if you can physically route the fill so the outlet is above the cistern rim and sized per Table 603.3.1. If an air gap is impractical and there’s no chemical injection or pump that could create backpressure, a listed vacuum breaker with critical level ≥ 6 inches may be acceptable.

Do I need annual testing for every backflow device on a single‑family property?

Yes — the code requires assemblies to be tested at installation/repair/relocation and not less than annually thereafter by a certified tester, or more often if the Authority Having Jurisdiction requires it.

Can I use a double‑check (DC) device for a pool fill line with chlorine?

No — where chemicals are introduced, the code typically requires a reduced‑pressure principle (RP) device or an air gap; Table 603.2 and § 603.5.10 indicate RP for connections where chemicals are used.

Is a simple downstream check valve adequate to prevent backflow?

No — the code requires listed backflow prevention assemblies or an air gap; ad hoc check valves or unlisted fittings do not meet the code. Use devices and installation methods listed in Table 603.2 and approved by the AHJ. file

Where in the Residential Code should I look for definitions like “backflow”?

Definitions are in the CRC definitions section (look for the [MP] plumbing definitions such as BACKFLOW and BACKFLOW PREVENTER). However, for installation requirements the CRC points you to the California Plumbing Code (Chapter 603 series). file

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