CPC · California Plumbing Code
How are irrigation systems, pools/spas and chemical dispensers protected from backflow?
For homeowners: irrigation systems without pumps can use vacuum breakers or PVBs, but if you have a pump or any chemical injector you must use a reduced‑pressure (RP) device; pools with submerged fills need an air gap or RP; chemical dispensers must be listed or protected by specific backflow assemblies — all per the California Plumbing Code §§ 603.5.6, 603.5.21, and 603.5.22.
Last reviewed: July 6, 2026
What the code requires — 2–4 sentences
Potable water supplies to irrigation systems must be protected from backsiphonage and backpressure by specific vacuum breakers or a reduced‑pressure principle backflow prevention assembly depending on pumps, downstream devices, or chemical injection per § 603.5.6. Potable fills to swimming pools, spas, and hot tubs require an air gap or an RP when there is a submerged fill line or a direct connection to the circulation system per § 603.5.21. Water to chemical dispensers must either be a listed chemical dispenser with integral protection or be protected by one of several listed devices (air gap, AVB, PVB, SVB, or RP) per § 603.5.22.
The single most important rule: always choose the backflow device required by the specific situation — pumps or chemical injection push you to a reduced‑pressure assembly (RP); submerged or direct filling of pools requires an air gap or RP.
Requirements in detail
Key devices (defined terms — first mention bolded)
- Air gap — a physical separation between the supply outlet and the flood‑level rim of the receiving vessel (see Table 603.3.1) (defined in Chapter 603).
- Atmospheric Vacuum Breaker (AVB) — a listed vacuum‑breaking device (see § 603.3.2).
- Pressure Vacuum Breaker (PVB) — a pressure‑type vacuum breaker assembly (see § 603.3.5).
- Spill‑resistant pressure vacuum breaker (SVB) — a pressure‑type vacuum breaker with spill‑resistant characteristics (see § 603.3.6).
- Reduced‑pressure principle backflow prevention assembly (RP) — an assembly with two checks and a differential relief valve (see § 603.3.7).
Decision table — which device to use
| Scenario / trigger | Allowed device(s) | Key installation notes (decision‑relevant) | Code Reference |
|---|---|---|---|
| Irrigation no pumps, no chemical injection | AVB, PVB, SVB, RP, or valve meeting IAPMO PS 72 | AVB/PVB/SVB common for irrigation; AVB cannot be under continuous pressure. | § 603.5.6 |
| Irrigation with pumps, booster connections, auxiliary tanks, or capable of creating backpressure (when backflow device is located upstream from the source of backpressure) | RP only | If device is upstream from pump/source of backpressure, RP is required. | § 603.5.6.1 |
| Irrigation with pump (device installed downstream of pump or pump connection) | AVB, PVB, SVB, or RP | Downstream‑installed devices may be these types; watch for continuous pressure limitations for AVB. | § 603.5.6.2 |
| Irrigation with chemical injector / fertigation provisions | RP only | Chemical injection qualifies as a high‑hazard condition; RP required. | § 603.5.6.3 |
| Swimming pool, spa, hot tub with submerged fill line or direct potable connection to circulation system | Air gap or RP | If fill line is submerged or supply ties into circulation system, use air gap or RP. | § 603.5.21 |
| Chemical dispensers (e.g., sanitizers, concentrates) | Listed chemical dispenser with integral protection (ANSI/CAN/ASSE/IAPMO 1055) OR air gap / AVB / PVB / SVB / RP | Manufacturer listing (1055) preferred; for faucet installations with an integrated vacuum breaker, a pressure‑bleed device per IAPMO PS 104 is required to protect the vacuum breaker. | § 603.5.22 and Table 603.2 (chemical dispenser listing) |
Installation and placement rules to watch
- AVB critical level: vacuum breakers listed for inlet or discharge must be installed at or above their listed critical level (see related rules for 6 in / 152 mm where applicable). For example, water supply inlets to tanks or receptors require either an air gap or a listed vacuum breaker with critical level not less than 6 inches (152 mm) above the flood‑level rim where specified. § 603.5.5 and § 603.5.1 contain these provisions.
- Deck‑/equipment‑mounted vacuum breakers must have a critical level not less than 1 inch (25.4 mm) above the flood‑level rim when listed for that installation.
- Devices with atmospheric vents or ports shall not be installed in pits, underground, or submerged locations. Avoid locations with toxic fumes or corrosion risk.
- Drain sizing: discharge/drain lines for devices (for example RP relief discharge) must be sized per the manufacturer’s flow charts. § 603.4.8.
Testing, maintenance, and approvals
- Backflow devices must be approved by the Authority Having Jurisdiction and listed to the applicable standard (see Table 603.2). § 603.2 and § 603.3–603.4 govern approvals.
- Devices and assemblies shall be tested at installation, after repair or relocation, and not less than annually (or more often if required by the Authority Having Jurisdiction). Testing must be performed by a certified backflow assembly tester/repairer (ASSE/IAPMO/ANSI Series 5000 or approved equivalent).
- For installations exposed to freezing conditions, backflow assemblies must be protected by an outdoor enclosure complying with ASSE 1060 or by an alternative acceptable to the AHJ. § 603.4.7.
Exceptions & special cases
- AVBs are not suitable where the device will be under continuous pressure — they are intended for intermittent service; consult § 603.3.2 and device listings. If continuous pressure exists, choose PVB, SVB, RP, or listed integral devices.
- If a backflow device is placed upstream of the pump (i.e., before the pump suction that could create backpressure), the code requires RP. If placed downstream, other devices are allowed per § 603.5.6.1–.2.
- For chemical dispensers, a compliant, listed dispenser with integral backflow protection (ANSI/CAN/ASSE/IAPMO 1055) may be used in lieu of field‑installed devices — this is allowed and referenced in Table 603.2 and § 603.5.22(1).
- Where pools/spas have a submerged fill line or the potable supply is directly connected to the circulation system, an air gap or RP is required (no other vacuum‑breaker types are listed as acceptable in § 603.5.21).
Common mistakes
- Installing an AVB on a continuously pressurized irrigation main (AVBs are not for continuous pressure). Failure to check listed device limitations is frequent.
- Placing vented devices (RP, PVB) in pits, underground, or submerged locations — vents/ports require open air per § 603.4.9.
- Choosing a device without confirming it is listed to the applicable standard (for example, chemical dispensers to ANSI/CAN/ASSE/IAPMO 1055 or beverage equipment to ASSE 1022) or without AHJ approval.
- Omitting annual testing or using uncertified testers — the code mandates periodic testing by certified personnel.
- Not accounting for pressure drop through a backflow device when sizing pumps or verifying hydraulic performance (relevant where devices are added to existing systems). See fire‑system guidance in § 603.5.14.3 and consult manufacturer data where applicable.
Worked example — residential irrigation with booster pump and fertilizer injector
Scenario: A homeowner has a potable water line feeding an irrigation controller and zone valves. A booster pump (downstream of the service) increases pressure for several zones. The system also has a chemical injector for fertilizer.
Step 1 — Identify triggers:
- System has a pump capable of creating backpressure → triggers the pump rules.
- System has a chemical injector → chemical injection triggers RP requirement.
Step 2 — Apply the code:
- § 603.5.6.3 requires an RP where systems include a chemical injector. Therefore, regardless of upstream/downstream placement, the potable supply must be protected by an RP. § 603.5.6.3.
Step 3 — Installation notes:
- Install a listed RP sized for the service flow; provide a proper discharge/drain sized per manufacturer flow charts (§ 603.4.8).
- Do not locate the RP in a pit or submerged location; provide freeze protection/enclosure if outdoor per § 603.4.7 and avoid areas with corrosive fumes (§ 603.4.9).
- Schedule initial test at installation and annual testing thereafter by a certified tester (ASSE/IAPMO/ANSI Series 5000).
Conclusion: The correct selection and required protective device for this scenario is a reduced‑pressure principle backflow prevention assembly (RP) per § 603.5.6.3.
Related provisions
- § 603.3 — Definitions and descriptions of backflow devices (AVB, PVB, SVB, RP).
- § 603.4 — General requirements: freeze protection, drain sizing, prohibited locations.
- Table 603.2 — Lists device standards and allowed uses (includes chemical dispenser listing to ANSI/CAN/ASSE/IAPMO 1055).
- § 603.5.5 — Water supply inlets to tanks/receptors — air gap / listed vacuum breaker requirements and critical levels.
- Appendix L, L 411 — Landscape irrigation additional requirements and backflow protection references.
Code references
Grounded in the retrieved California Plumbing Code — click a citation to read the verbatim passage:
CPC § 603.5.17 High relevance — show source text
603.5.17 Potable Water Outlets and Valves. Potable water outlets, freeze-proof yard hydrants, combination stop-and-waste valves, or other fixtures that incorporate a stop and waste feature that drains into the ground shall not be installed underground. 603.5.18 Pure Water Process Systems. The water supply to a pure water process system, such as dialysis water systems, semiconductor washing systems, and similar process piping systems, shall be protected from backpressure and backsiphonage by a reduced-pressure principle backflow preventer. 603.5.18.1 Dialysis Water Systems. The individual connections of the dialysis related equipment to the dialysis pure water system shall not require additional backflow protection. 603.5.19 Garbage Can Washers. Where garbage can washers are connected to a potable water supply system, the connection shall be protected against backflow in accordance with Table 603.2.
603.5.20 Plumbing Fixture Fittings. Plumbing fixture fittings with integral backflow protection shall comply with ASME A112.18.1/CSA B125.1. 603.5.21 Swimming Pools, Spas, and Hot Tubs. Potable water supply to swimming pools, spas, and hot tubs shall be protected by an air gap or a reduced pressure principle backflow preventer in accordance with the following:
(1) The unit is equipped with a submerged fill line.
(2) The potable water supply is directly connected to the unit circulation system. 603.5.22 Chemical Dispensers. The water supply to chemical dispensers shall be protected against backflow by one of the following:
(1) The chemical dispenser shall comply with ANSI/CAN/ASSE/IAPMO 1055. Where an installation involves a water source coming from a faucet with an integrated vacuum breaker device, a pressure bleed device conforming to IAPMO PS 104 shall be used to protect the vacuum breaker device.
(2) Water supply shall be protected by one of the following methods:
(a) Air gap
(b) Atmospheric vacuum breaker (AVB)
(c) Pressure vacuum breaker backflow prevention assembly (PVB)
(d) Spill-resistant pressure vacuum breaker (SVB)
(e) Reduced-pressure principle backflow prevention assembly (RP)
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604.0 Materials.
604.1 Pipe, Tube, and Fittings. Pipe, tube, fittings, solvent cement, thread sealants, solders, and flux used in potable water systems intended to supply drinking water shall comply with NSF/ANSI/CAN 61. Where pipe fittings and valves are made from copper alloys containing more than 15 percent zinc by weight and are used in plastic piping systems, they shall be resistant to dezincification and stress corrosion cracking in compliance with NSF/ANSI 14.
Materials used in the water supply system, except valves and similar devices, shall be of a like material, except where otherwise approved by the Authority Having Jurisdiction.
Materials for building water piping and building supply piping shall comply with the applicable standards referenced in Table 604.1.
CPC § 603.5.6.1 High 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).
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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 METHOD1APPLICABLE
STANDARDSPOLLUTION
(LOW HAZARD)POLLUTION
(LOW HAZARD)CONTAMINATION
(HIGH HAZARD)CONTAMINATION
(HIGH HAZARD)INSTALLATION2,3 DEVICE, ASSEMBLY,
OR METHOD1APPLICABLE
STANDARDSBACK-
SIPHONAGEBACK-
PRESSUREBACK-
SIPHONAGEBACK-
PRESSUREBACK-
PRESSUREAir gap ASME
A112.1.2X –– X –– See Table 603.3.1 in this chapter. Air gap fittings for use
with plumbing fixtures,
appliances, and appurte-
nancesASME
A112.1.3X –– X –– Air gap fitting is a device with an internal air
gap, and typical installation includes
plumbing fixtures, appliances,CPC § 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).
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CPC § 603.5.9 High 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:
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CPC § 603.4.5 High relevance — show source text
603.4.5 Hot Water Backflow Preventers. Backflow preventers for hot water exceeding 110°F (43°C) shall be a type designed to operate at temperatures exceeding 110°F (43°C) without rendering a portion of the assembly inoperative. 603.4.6 Integral Backflow Preventers. Fixtures, appliances, or appurtenances with integral backflow preventers or integral air gaps manufactured as a unit shall be installed in accordance with their listing requirements and the manufacturer’s installation instructions.
603.4.7 Freeze Protection. In cold climate areas, backflow assemblies and devices shall be protected from freezing with an outdoor enclosure that complies with ASSE 1060 or by a method acceptable to the Authority Having Jurisdiction. 603.4.8 Drain Lines. Drain lines serving backflow devices or assemblies shall be sized in accordance with the discharge rates of the manufacturer’s flow charts of such devices or assemblies.
603.4.9 Prohibited Locations. Backflow prevention devices with atmospheric vents or ports shall not be installed in pits, underground, or submerged locations. Backflow preventers shall not be located in an area containing fumes that are toxic, poisonous, or corrosive. 603.5 Specific Requirements. Specific requirements for backflow prevention shall comply with Section 603.5.1 through Section 603.5.22. 603.5.1 Atmospheric Vacuum Breaker. Water closet and urinal flushometer valves shall be protected against backflow by an approved backflow prevention assembly, device, or method. Where the valves are equipped with an atmospheric vacuum breaker, the vacuum breaker shall be installed on the discharge side of the flushometer valve with the critical level not less than 6 inches (152 mm), or the distance according to its listing, above the overflow rim of a water closet bowl or the highest part of a urinal.
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.
CPC § 603.5.14.2 High relevance — show source text
(1) Reduced pressure principle backflow prevention assembly (RP)
(2) Reduced pressure detector fire protection backflow prevention assembly
Nonpotable water sources include fire department vehicles carrying water of questionable quality or water that is treated with antifreeze, corrosion inhibitors, or extinguishing agents. 603.5.14.2 Chemicals. Where antifreeze, corrosion inhibitors, or other chemicals are added to a fire protection system supplied from a potable water supply, the potable water system shall be protected by one of the following:
(1) Reduced pressure principle backflow prevention assembly (RP)
(2) Reduced pressure detector fire protection backflow prevention assembly 603.5.14.3 Hydraulic Design. Where a backflow device is installed in the potable water supply to a fire protection system, the hydraulic design of the system shall account for the pressure drop through the backflow device. Where such devices are retrofitted for an existing fire protection system, the hydraulics of the sprinkler system design shall be checked to verify that there will be sufficient water pressure available for satisfactory operation of the fire sprinklers. 603.5.15 Health Care or Laboratory Areas. Vacuum breakers for washer-hose bedpans shall be located not less than 5 feet (1524 mm) above the floor. Hose con
nections in health care or laboratory areas shall be not less than 6 feet (1829 mm) above the floor. 603.5.16 Special Equipment. Portable cleaning equipment and dental vacuum pumps shall be protected from backflow by an air gap, an atmospheric vacuum breaker, a spill-resistant vacuum breaker, or a reduced pressure principle backflow preventer.
603.5.17 Potable Water Outlets and Valves. Potable water outlets, freeze-proof yard hydrants, combination stop-and-waste valves, or other fixtures that incorporate a stop and waste feature that drains into the ground shall not be installed underground. 603.5.18 Pure Water Process Systems. The water supply to a pure water process system, such as dialysis water systems, semiconductor washing systems, and similar process piping systems, shall be protected from backpressure and backsiphonage by a reduced-pressure principle backflow preventer. 603.5.18.1 Dialysis Water Systems. The individual connections of the dialysis related equipment to the dialysis pure water system shall not require additional backflow protection. 603.5.19 Garbage Can Washers. Where garbage can washers are connected to a potable water supply system, the connection shall be protected against backflow in accordance with Table 603.2.
603.5.20 Plumbing Fixture Fittings. Plumbing fixture fittings with integral backflow protection shall comply with ASME A112.18.1/CSA B125.1. 603.5.21 Swimming Pools, Spas, and Hot Tubs. Potable water supply to swimming pools, spas, and hot tubs shall be protected by an air gap or a reduced pressure principle backflow preventer in accordance with the following:
(1) The unit is equipped with a submerged fill line.
(2) The potable water supply is directly connected to the unit circulation system. 603.5.22 Chemical Dispensers. The water supply to chemical dispensers shall be protected against backflow by one of the following:
CPC § 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.
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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.
CPC § 603.5.14.1 High relevance — show source text
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(1) American Water Works Association [A.W.W.A] Manual No. M-14 class 1 – Automatic fire sprinkler systems with direct connection from public water mains only; no pumps, tanks, or reservoirs; no physical connection from other water supplies; no antifreeze or additives of any kind; and all sprinkler drains discharging to the atmosphere or other safe outlets.
(2) American Water Works Association [A.W.W.A] Manual No. M-14 class 2 – Automatic fire sprinkler systems which are the same as class 1, except that booster pumps may be installed in the connections from the street mains.
(b) Automatic fire sprinkler systems described in subdi- vision (a) shall not require any backflow protection equipment at the service connection other than required by standards for those systems contained in the publication of the National Fire Protection Association entitled “Installation of Sprinkler Sys- tems” [NFPA Pamphlet No. 13, 1980 edition]. 603.5.14.1 Fire Department Connection. Where fire protection systems supplied from a potable water system include a fire department (siamese) connection that is located less than 1700 feet (518.2 m) from a nonpotable water source that is capable of being used by the fire department as a secondary water supply, the potable water supply shall be protected by one of the following:
(1) Reduced pressure principle backflow prevention assembly (RP)
(2) Reduced pressure detector fire protection backflow prevention assembly
Nonpotable water sources include fire department vehicles carrying water of questionable quality or water that is treated with antifreeze, corrosion inhibitors, or extinguishing agents. 603.5.14.2 Chemicals. Where antifreeze, corrosion inhibitors, or other chemicals are added to a fire protection system supplied from a potable water supply, the potable water system shall be protected by one of the following:
(1) Reduced pressure principle backflow prevention assembly (RP)
(2) Reduced pressure detector fire protection backflow prevention assembly 603.5.14.3 Hydraulic Design. Where a backflow device is installed in the potable water supply to a fire protection system, the hydraulic design of the system shall account for the pressure drop through the backflow device. Where such devices are retrofitted for an existing fire protection system, the hydraulics of the sprinkler system design shall be checked to verify that there will be sufficient water pressure available for satisfactory operation of the fire sprinklers. 603.5.15 Health Care or Laboratory Areas. Vacuum breakers for washer-hose bedpans shall be located not less than 5 feet (1524 mm) above the floor. Hose con
nections in health care or laboratory areas shall be not less than 6 feet (1829 mm) above the floor. 603.5.16 Special Equipment. Portable cleaning equipment and dental vacuum pumps shall be protected from backflow by an air gap, an atmospheric vacuum breaker, a spill-resistant vacuum breaker, or a reduced pressure principle backflow preventer.
**603.5.17 Potable Water Outlets and Valves.
CPC § 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
), 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,
CPC § 603.2 High relevance — show source text
| |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
), 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 (continued) 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 METHOD1APPLICABLE
STANDARDSPOLLUTION
(LOW HAZARD)POLLUTION
(LOW HAZARD)CONTAMINATION
(HIGH HAZARD)CONTAMINATION
(HIGH HAZARD)INSTALLATION2,3 DEVICE, ASSEMBLY,
OR METHOD1APPLICABLE
STANDARDSBACK-
SIPHONAGEBACK-
PRESSUREBACK-
SIPHONAGEBACK-
PRESSUREBACK-
PRESSUREDouble Check Valve
Backflow Prevention
Assembly (two inde-
pendent check valves
and means of field test-
ing)ASSE 1015;
AWWA C510;
CSA B64.5 or
CSA B64.5.1X X –– –– Horizontal unless otherwise listed. CPC § 603.3 High 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.
CPC § 408.4.2 High relevance — show source text
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|1007.2| |ASSE 1047-2021|Reduced Pressure Detector Backflow Prevention Assemblies|Backflow Protection|Table 603.2| |ASSE 1048-2021|Double Check Detector Backflow Prevention Assemblies|Backflow Protection|Table 603.2| |ASSE 1052-2016|Hose Connection Backflow Preventers|Backflow Protection|Table 603.2| |ASSE 1053-2019|Dual Check Backflow Preventer Wall Hydrants – Freeze
Resistant Type|Backflow Protection|Table 603.2| |ANSI/CAN/ASSE/IAPMO
1055-2020|Chemical Dispensers with Integral Backflow Protection|Backflow Protection|Table 603.2,
603.5.22(1)| |ASSE 1056-2013 (R2021)|Spill Resistant Vacuum Breaker Assemblies|Backflow Protection|Table 603.2| |ASSE 1057-2012|Freeze Resistant Sanitary Yard Hydrants with Backflow Pro-
tection|Backflow Protection|Table 603.2| |ASSE 1060-2017|Outdoor Enclosures for Fluid Conveying Components with
Errata dated February 1, 2019|Miscellaneous|603.4.7| |ASSE 1061-2020|Push-Fit Fittings|Fittings|Table 604.1,
605.1.3.3, 605.2.1.1,
605.3.2.1, 605.9.3| |ASSE 1062-2017 (R2021)|Temperature Actuated, Flow Reduction (TAFR) Valves for
Individual Supply Fittings|Valves|408.4.3, 417.
Frequently asked questions
Can I use an AVB on an irrigation main that is under constant pressure?
No. An AVB is not suitable for continuously pressurized mains; use a PVB, SVB, RP, or a listed integral device appropriate to the hazard and installation.
My pool has a submerged fill line — do I need an RP or is an air gap allowed?
Either an air gap or a reduced‑pressure principle backflow prevention assembly (RP) is required where the unit has a submerged fill line or the potable supply is directly tied into the circulation system. § 603.5.21.
Are chemical dispensers allowed to rely on an integral device?
Yes — a chemical dispenser listed to ANSI/CAN/ASSE/IAPMO 1055 with integral protection is an acceptable option; otherwise protect the supply with one of the listed assemblies or an air gap. § 603.5.22 and Table 603.2.
How often must backflow devices be tested?
Devices must be tested at installation, after repair/relocation, and not less than annually, or more frequently if the Authority Having Jurisdiction requires it; testing must be by a certified tester.
Can I install an RP in a pit or underground?
No. Devices with atmospheric vents or ports (including many RPs and vented devices) shall not be installed in pits, underground, or submerged locations; install in accessible, vented locations per § 603.4.9.
More in California Plumbing Code
- Administration
- Definitions
- General Regulations
- Plumbing Fixtures and Fixture Fittings
- Water Heaters
- Water Supply and Distribution
- Sanitary Drainage (Drain, Waste, and Vent)
- Indirect Wastes
- Vents
- Traps and Interceptors
- Storm Drainage
- Fuel Gas Piping
- Health Care Facilities — Medical Gas and Medical Vacuum Systems
- Alternate Water Sources and Nonpotable Rainwater Catchment Systems
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