CPC · California Plumbing Code

What are the rules for potable and nonpotable rainwater catchment systems and connections?

You must submit and get AHJ approval for rainwater catchment plans; the CPC forbids direct connections to potable water (makeup or temporary hookup only with an air gap or approved backflow protection and only as allowed for tests); sizing must follow Chapter 11; testing/initial cross‑connection procedures and minimum hold times apply.

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Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

The California Plumbing Code requires that rainwater catchment systems be planned, permitted and approved by the Authority Having Jurisdiction and that no direct connection exists between rainwater systems and potable water supplies unless specific protections are provided. Key controlling sections are § K 102.1, § K K 102.2, § 1602.4, and § 1602.6.

The single most important rule: a rainwater catchment system must not be directly plumbed into a potable water system — makeup or temporary test connections are only allowed if the code-prescribed protection (for example, an air gap or approved backflow device) and AHJ approval are provided.

Requirements in detail

Permits and plan submission

A complete plumbing plan approved by the Authority Having Jurisdiction is required before a permit will be issued for a rainwater catchment system. This is mandatory for systems that require permits. See § 1602.2 and § K 101.3.1.

Prohibited direct connections (core rule)

No direct connection is permitted between a rainwater catchment system and a potable water supply or alternate water source system. Any connection that would allow two systems to mix is disallowed unless the specific exceptions/protections in code are provided. See § 1602.4 and § K 102.2.

Allowed makeup / temporary connections and required protection

Makeup water from a potable, on-site treated graywater, or reclaimed (recycled) water supply is permitted only if the connection is protected by an air gap or other approved device (for example, a reduced-pressure principle backflow preventer) in accordance with the code. See § 1602.4 and § K 102.2.
A potable supply may be connected temporarily for the initial cross‑connection test only (see § 1602.4, exception).

Cross‑connection testing and inspection

An initial cross‑connection test (visual + pressure/flow procedures) must be performed prior to system activation/occupancy and in the presence of the AHJ; the AHJ must rule the test successful before final approval. During tests potable and rainwater systems are isolated and inspected per the procedures in Chapter 16 (see § 1602.5, § 1605.3).
The potable system must remain depressurized while the rainwater system is pressurized for a minimum time determined by the AHJ, but not less than 1 hour.

Sizing and design

Drainage components — gutters, conductors, downspouts, and leaders — must be sized per Chapter 11 of the CPC; the code explicitly requires compliance with Chapter 11 for sizing. See § 1602.6.

Materials, markings, maintenance (potable vs nonpotable)

Potable rainwater systems must use materials listed/labeled for potable use; collection surfaces for potable use must be approved and constructed of hard, impervious materials (Appendix K provisions). See § K 103.1 and related K sections.
Nonpotable systems must be colored/marked and labeled with caution wording (for example: “CAUTION: NONPOTABLE RAINWATER, DO NOT DRINK.”) per § 1602.8 / § 1603.11.
Maintenance and testing frequencies for potable systems are set out in Appendix K tables (filters, water-quality tests, frequency) and must be kept in a maintenance log. See Table K 101.5.1 and § K 101.5.2.

Separation and trenching

Underground treated nonpotable and potable piping may be run in the same trench only with minimum vertical and horizontal separation of 12 inches (305 mm) when materials are approved; otherwise separation must be increased to 60 inches (1524 mm). Potable piping must be installed above the nonpotable piping. See § 1601.10.

Decision-relevant table

Decision item	Requirement / value	Code Reference
Direct connection between rainwater and potable supply	Prohibited (no direct connection)	§ 1602.4
Makeup water allowed?	Yes, only if protected by an air gap or approved backflow device (e.g., RPBP)	§ 1602.4 / § K 102.2
Temporary potable connection for testing	Permitted for initial cross‑connection test only	§ 1602.4 (Exception 2)
Plan submission before permit	Complete plumbing plans required and approval by AHJ	§ 1602.2 / § K 101.3.1
Cross‑connection test hold time	AHJ determines; minimum 1 hour depressurized	§ 1605.3.2 / § 1602.5
Sizing of gutters/downspouts/leaders	Comply with Chapter 11 sizing rules	§ 1602.6
Underground pipe separation	12 in (305 mm) min vertical/horizontal (or 60 in (1524 mm) if materials don't meet reqs)	§ 1601.10
Small irrigation exception	No treatment required for aboveground irrigation tanks ≤ 360 gallons (1363 L)	§ 1601.7 (Exception)

Exceptions & special cases

Makeup water is allowed when protected by an air gap or an approved backflow-prevention assembly; this is the primary exception to the “no direct connection” rule. See § 1602.4 and § K 102.2.
A potable supply can be temporarily connected only for the initial cross‑connection test; the temporary connection must be removed after testing. See § 1602.4 (Exception 2).
Small, aboveground irrigation systems with maximum storage ≤ 360 gallons may be exempted from treatment requirements (nonpotable) — check § 1601.7 exceptions and confirm with AHJ.
Appendix K (potable rainwater design) is an appendix and applies where adopted; potable rainwater systems also require design by a registered design professional or competent person when required. See § K 101.2 and K 101.3.

If a specific clause above is not covered in the retrieved excerpts (for example, an AHJ local amendment), the code text for that precise local rule may not be in the materials I reviewed — confirm local AHJ policies.

Common mistakes

Assuming a simple valve or check valve is sufficient protection for makeup water — the code requires an air gap (or other specifically approved device) for makeup water connections to storage. See § 1602.4 and § K 102.2.
Forgetting to submit full plumbing plans — permits are withheld until complete plumbing plans satisfactory to the AHJ are approved (§ 1602.2 / § K 101.3.1).
Not performing the initial cross‑connection test in the presence of the AHJ, or not keeping the potable system depressurized for the minimum required time (AHJ-determined but not less than 1 hour) — causes delays or rejection. See § 1602.5 and § 1605.3.2.
Running underground nonpotable and potable pipes without required separation (minimum 12 in (305 mm) or 60 in (1524 mm) where materials differ) — leads to compliance failure. See § 1601.10.

Worked example — concrete scenario

Scenario: A commercial building owner plans a rainwater catchment system that will supply irrigation and toilet flushing. The system includes rooftop collection, a 2,000‑gallon aboveground storage tank, and pumps to toilets and landscape irrigation.

Step-by-step application of the rules:

Plan submission and permit: Submit complete plumbing plans to the AHJ before any permit is issued (see § 1602.2).
Direct connections: Because the system will serve toilets, it cannot be directly connected to the potable water system. Any makeup potable water must enter the storage tank only through an air gap or an approved reduced‑pressure backflow preventer; document this in the plans (see § 1602.4 and § K 102.2).
Cross‑connection test: Arrange the initial cross‑connection test with the AHJ present. A temporary potable hookup may be used for the test if needed, but it must be disconnected at test conclusion. During testing the AHJ will require the potable system to remain depressurized while the rainwater system is pressurized for a minimum period (not less than 1 hour). Document and schedule per § 1602.5 / § 1605.3.2.
Sizing: Size gutters, leaders and downspouts per Chapter 11 to handle the design rainfall for the roof area; reference § 1602.6 in your calculations and plans.
Piping separation: If any treated nonpotable piping runs in the same trench as potable supply lines, ensure 12 in (305 mm) minimum separation (or 60 in (1524 mm) if materials don’t meet the prescriptive criteria), with potable piping above. Show this on your trenching detail per § 1601.10.
Materials and labels: For toilet supply (potable‑grade or potable‑treated rainwater) use listed potable materials and maintain required labeling, maintenance logs and testing frequencies (Appendix K requirements for potable systems if potable rainwater route is adopted).

Related provisions (quick reference)

§ 1602.2 — Plumbing plan submission and permit requirement.
§ 1602.5 / § 1605.3 — Initial cross‑connection test procedures and inspection/testing requirements.
§ 1601.10 — Separation requirements for potable and nonpotable piping (12 in / 60 in).
§ 1601.7 — Minimum water quality and exceptions (e.g., 360‑gallon exception for some irrigation).
§ K 101.3.1 / K 101.2 — Appendix K permit and design (potable rainwater systems; designer and seismic restraint requirements where adopted).
§ K 101.5 / Table K 101.5.1 — Testing, inspection and maintenance frequency for potable rainwater systems.

Code references

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

CPC § 1602.2 High relevance — show source text
** The installation, construction, alteration, and repair of rainwater catchments systems intended to supply uses such as water closets, urinals, trap primers for floor drains and floor sinks, irrigation, industrial processes, water features, cooling tower makeup and other uses shall be approved by the Authority Having Jurisdiction. Rainwater catchment systems for collecting precipitation from rooftops shall comply with ARCSA/ASPE/ANSI 63. 1602.2 Plumbing Plan Submission. No permit for a rainwater catchment system shall be issued until complete plumbing plans, with data satisfactory to the Authority Having Jurisdiction, have been submitted and approved. 1602.3 System Changes. No changes or connections shall be made to either the rainwater catchment system or the potable water system within a site containing a rainwater catchment system requiring a permit without approval by the Authority Having Jurisdiction. 1602.4 Connections to Potable or Reclaimed (Recy- cled) Water Systems. Rainwater catchment systems shall have no direct connection to a potable water supply or alternate water source system. Exceptions: (1) Potable water, on-site treated nonpotable gray water, or reclaimed (recycled) water is permitted to be used as makeup water for a rainwater catchment system provided the connection is protected by an air gap in accordance with this code.

(2) A potable water supply may be connected temporarily for the initial cross-connection test of the rainwater catchment system as required in Section 1605.3.2. 1602.5 Initial Cross-Connection Test. Where a portion of a rainwater catchment system is installed within a building, a cross-connection test is required in accordance with Section 1605.3. Before the building is occupied or the system is activated, the installer shall perform the initial cross-connection test in the presence of the Authority Having Jurisdiction and other authorities having jurisdiction. The test shall be ruled successful by the Authority Having Jurisdiction before final approval is granted. 1602.6 Sizing. The design and size of rainwater drains, gutters, conductors, and leaders shall comply with Chapter 11 of this code.

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NONPOTABLE RAINWATER CATCHMENT SYSTEMS

1602.7 Rainwater Catchment System Materials. Rain- 1603.3 Rainwater Catchment Collection Surfaces. water catchment system materials shall comply with Section Rainwater shall be collected from roof surfaces or other 1602.7.1 through Section 1602.7.3 . impervious manmade, aboveground collection surfaces. 1602.7.1 Water Supply and Distribution Materi- 1603.3.1 Other Surfaces. Natural precipitation colals. Rainwater catchment water supply and distribution lected from surface water runoff, vehicular parking surmaterials shall comply with the requirements of this code faces, or manmade surfaces at or below grade shall be in for potable water supply and distribution systems unless accordance with the water quality requirements for onotherwise provided for in this section. site treated nonpotable gray water systems in Section

1506.0.

1602.7.2 Rainwater Catchment System Drainage Materials. Materials used in rainwater catchment Exception: Collected rainwater or storm water used
CPC § 1601.10 High relevance — show source text
1601.10 Separation Requirements. Underground rainwater catchment service piping shall be separated from the building sewer in accordance with Section 609.2. Treated nonpotable water pipes shall be permitted to be run or laid in the same trench as potable water pipes with a 12 inch (305 mm) minimum vertical and horizontal separation where both pipe materials are approved for use within a building. Where horizontal piping materials do not meet this requirement, the minimum separation shall be increased to 60 inches (1524 mm). The potable water piping shall be installed at an elevation above the treated nonpotable water piping. 1601.11 Abandonment. Rainwater catchment systems that are no longer in use, or fail to be maintained in accordance with Section 1601.5, shall be abandoned. Abandonment shall comply with Section 1601.11.1 and Section 1601.11.2.

1601.11.1 General. An abandoned system or part thereof covered under the scope of this chapter shall be disconnected from remaining systems, drained, plugged, and capped in an approved manner. 1601.11.2 Underground Tank. An underground water storage tank that has been abandoned or otherwise discontinued from use in a system covered under the scope of this chapter shall be completely drained and filled with earth, sand, gravel, concrete, or other approved material or removed in a manner satisfactory to the Authority Having Jurisdiction. 1601.12 Sizing. Unless otherwise provided for in this chapter, rainwater catchment piping shall be sized in accordance with Chapter 6 for sizing potable water piping.

1602.0 Nonpotable Rainwater Catchment Systems. 1602.1 General. The installation, construction, alteration, and repair of rainwater catchments systems intended to supply uses such as water closets, urinals, trap primers for floor drains and floor sinks, irrigation, industrial processes, water features, cooling tower makeup and other uses shall be approved by the Authority Having Jurisdiction. Rainwater catchment systems for collecting precipitation from rooftops shall comply with ARCSA/ASPE/ANSI 63. 1602.2 Plumbing Plan Submission. No permit for a rainwater catchment system shall be issued until complete plumbing plans, with data satisfactory to the Authority Having Jurisdiction, have been submitted and approved. 1602.3 System Changes. No changes or connections shall be made to either the rainwater catchment system or the potable water system within a site containing a rainwater catchment system requiring a permit without approval by the Authority Having Jurisdiction. 1602.4 Connections to Potable or Reclaimed (Recy- cled) Water Systems. Rainwater catchment systems shall have no direct connection to a potable water supply or alternate water source system. Exceptions: (1) Potable water, on-site treated nonpotable gray water, or reclaimed (recycled) water is permitted to be used as makeup water for a rainwater catchment system provided the connection is protected by an air gap in accordance with this code.

(2) A potable water supply may be connected temporarily for the initial cross-connection test of the rainwater catchment system as required in Section 1605.3.2. 1602.5 Initial Cross-Connection Test. Where a portion of a rainwater catchment system is installed within a building, a cross-connection test is required in accordance with Section 1605.3.
CPC § 1605.3.3 High relevance — show source text
NONPOTABLE RAINWATER CATCHMENT SYSTEMS

(3) Fixtures, potable, and rainwater shall be tested and inspected for flow. Flow from a rainwater catchment water system outlet shall indicate a cross-connection. No flow from a potable water outlet shall indicate that it is connected to the rainwater system.

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

(5) The potable water system shall then be completely drained.

(6) The rainwater catchment water system shall then be activated and pressurized. When rainwater is not available for the initial cross-connection test, a tem- porary connection to a potable water supply shall be required. At the conclusion of the initial cross- connection test, the temporary connection to the potable water supply shall be disconnected.

(7) The rainwater catchment water system shall remain pressurized for a minimum period of time specified by the Authority Having Jurisdiction while the potable water system is empty. The minimum 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) Fixtures, potable and rainwater catchment, shall be tested and inspected for flow. Flow from a potable water system outlet shall indicate a cross-connection. No flow from a rainwater catchment water outlet shall 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 period.

(10)Where there is no flow detected in the fixtures which would indicate a cross-connection, the potable water system shall be repressurized. 1605.3.3 Discovery of Cross-Connection. In the event that a cross-connection is discovered, the following procedure, in the presence of the Authority Having Jurisdiction, shall be activated immediately:

(1) Rainwater catchment piping to the building shall be shutdown at the supply source(s), and the rainwater riser shall be drained.

(2) Potable water piping to the building shall be shutdown at the meter.

(3) The cross-connection shall be uncovered and disconnected.

(4) The building shall be retested following procedures listed in Section 1605.3.1 and Section 1605.3.2.

(5) The potable water system shall be chlorinated with 50 ppm chlorine for 24 hours.

(6) The potable water system shall be flushed after 24 hours, and a standard bacteriological test shall be performed. Where test results are acceptable, the potable water system shall be permitted to be recharged.

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CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE

CHAPTER 17 - REFERENCED STANDARDS

(Matrix Adoption Tables are non-regulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)
CPC § 101.3.2 High relevance — show source text
** No permit for a rainwater catchment system requiring a permit shall be issued until complete plumbing plans, with data satisfactory to the Authority Having Jurisdiction, have been submitted and approved. No changes or connections shall be made to either the rainfall catchment or the potable water system within a site containing a rainwater catchment water system without approval by the Authority Having Jurisdiction. K 101.3.2 System Changes. No changes or connections shall be made to either the rainwater catchment system or the potable water system within a site containing a rainwater catchment system requiring a permit without approval by the Authority Having Jurisdiction. K 101.4 Product and Material Approval. System components shall be properly identified as to the manufacturer. K 101.4.1 Plumbing Materials and Systems. Pipe, pipe fittings, traps, fixtures, material, and devices used in a potable rainwater system shall be listed or labeled (thirdparty certified) by a listing agency (accredited conformity assessment body) and shall be in accordance with approved applicable recognized standards referenced within this code, and shall be free from defects. Unless otherwise provided for in this appendix, materials, fixtures, or devices used or entering into the construction of plumbing systems, or parts thereof shall be submitted to the Authority Having Jurisdiction for approval.

K 101.5 Maintenance and Inspection. Potable rainwater catchment systems and components shall be inspected and maintained in accordance with Section K 101.5.1 through Section K 101.5.3.

K 101.5.1 Frequency. Potable rainwater catchment systems and components shall be inspected and maintained in accordance with Table K 101.5.1 unless more

frequent inspection and maintenance are required by the manufacturer.

K 101.5.2 Maintenance Log. A maintenance log for potable rainwater catchment systems shall be maintained by the property owner and be available for inspection. The property owner or designated appointee shall ensure that a record of testing, inspection, and maintenance in accordance with Table K 101.5.1 is maintained in the log. The log will indicate the frequency of inspection, and maintenance of each system. A record of the required water quality tests shall be retained for not less than 2 years.

K 101.5.3 Maintenance Responsibility. The required maintenance and inspection of potable rainwater catchment systems shall be the responsibility of the property owner unless otherwise required by the Authority Having Jurisdiction.

K 101.6 Operation and Maintenance Manual. An operation and maintenance manual for potable rainwater catchment systems shall be supplied to the building owner by the system designer. The operating and maintenance manual shall include the following:

(1) Detailed diagram of the entire system and the location of system components.

(2) Instructions for operating and maintaining the system.

(3) Details on maintaining the required water quality as determined by the Authority Having Jurisdiction.

(4) Details on deactivating the system for maintenance, repair, or other purposes.

(5) Applicable testing, inspection, and maintenance frequencies in accordance with Table K 101.5.1.

(6) A method of contacting the manufacturer(s).
CPC § 1603.19 High relevance — show source text
1603.19 Roof Gutters. Gutters shall maintain a minimum slope and be sized in accordance with Section 1103.3.

1603.20 Rainwater Diversion Valves. Rainwater diversion valves ranging from 2 inches (50 mm) through 12 inches (300 mm) in diameter shall be an approved diverter valve . Valves shall be readily accessible and include a filter located upstream of the valve when required.

1604.0 Signs. 1604.1 General. Signs in buildings using rainwater shall be in accordance with Section 1604.2 and Section 1604.3 , and applicable requirements of the California Building Code .

1604.2 Commercial, Industrial, Institutional and Res- idential Restroom Signs. A sign shall be installed in restrooms in commercial, industrial, and institutional occupancies , and in residential common use areas using nonpotable rainwater for water closets, urinals, or both. Signs shall comply with all applicable requirements of the Califor- nia Building Code. Each sign shall contain the following text:

TO CONSERVE WATER, THIS BUILDING USES RAINWATER TO FLUSH TOILETS AND URINALS.

1604.3 Equipment Room Signs. Each equipment room containing nonpotable rainwater equipment shall have a sign posted with the following wording in 1 inch (25.4 mm) let ters:

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NONPOTABLE RAINWATER CATCHMENT SYSTEMS

(3) Fixtures, potable, and rainwater shall be tested and inspected for flow. Flow from a rainwater catchment water system outlet shall indicate a cross-connection. No flow from a potable water outlet shall indicate that it is connected to the rainwater system.

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

(5) The potable water system shall then be completely drained.

(6) The rainwater catchment water system shall then be activated and pressurized. When rainwater is not available for the initial cross-connection test, a tem- porary connection to a potable water supply shall be required. At the conclusion of the initial cross- connection test, the temporary connection to the potable water supply shall be disconnected.

(7) The rainwater catchment water system shall remain pressurized for a minimum period of time specified by the Authority Having Jurisdiction while the potable water system is empty. The minimum 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) Fixtures, potable and rainwater catchment, shall be tested and inspected for flow. Flow from a potable water system outlet shall indicate a cross-connection. No flow from a rainwater catchment water outlet shall 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 period.
CPC § 1601.5. High relevance — show source text
(3) Instructions on maintaining the required water quality as for rainwater catchment systems .

(4) Details startup, shutdown, and deactivating the system for maintenance, repair, or other purposes.

(5) Applicable testing, inspection, and maintenance frequencies in accordance with Section 1601.5.

(6) A method of contacting the installer and/or manufacturer(s).

(7) Directions to the owner or occupant that the manual shall remain with the building throughout the life cycle of the structure.

1601.7 Minimum Water Quality Requirements. The minimum water quality for rainwater catchment systems shall comply with the applicable water quality requirements for the intended application as determined by the Authority Having Jurisdiction. Water quality for nonpotable rainwater catchment systems shall comply with Section 1603.4. In the absence of water quality requirements for harvested rainwa- ter, Table 1603.4 shall apply.

Exceptions:

(1) Water treatment is not required for rainwater catchment systems used for aboveground irrigation with a maximum storage capacity of 360 gallons (1363 L).

(2) Water treatment is not required for rainwater catchment systems used for surface, subsurface or drip irrigation. 1601.8 Material Compatibility. Rainwater catchment systems shall be constructed of materials that are compatible with the type of pipe and fitting materials, water treatment, and water conditions in the system. 1601.9 System Controls. Controls for pumps, valves, and other devices that contain mercury that come in contact with rainwater supply shall not be permitted. 1601.10 Separation Requirements. Underground rainwater catchment service piping shall be separated from the building sewer in accordance with Section 609.2. Treated nonpotable water pipes shall be permitted to be run or laid in the same trench as potable water pipes with a 12 inch (305 mm) minimum vertical and horizontal separation where both pipe materials are approved for use within a building. Where horizontal piping materials do not meet this requirement, the minimum separation shall be increased to 60 inches (1524 mm). The potable water piping shall be installed at an elevation above the treated nonpotable water piping. 1601.11 Abandonment. Rainwater catchment systems that are no longer in use, or fail to be maintained in accordance with Section 1601.5, shall be abandoned. Abandonment shall comply with Section 1601.11.1 and Section 1601.11.2.

1601.11.1 General. An abandoned system or part thereof covered under the scope of this chapter shall be disconnected from remaining systems, drained, plugged, and capped in an approved manner. 1601.11.2 Underground Tank. An underground water storage tank that has been abandoned or otherwise discontinued from use in a system covered under the scope of this chapter shall be completely drained and filled with earth, sand, gravel, concrete, or other approved material or removed in a manner satisfactory to the Authority Having Jurisdiction. 1601.12 Sizing. Unless otherwise provided for in this chapter, rainwater catchment piping shall be sized in accordance with Chapter 6 for sizing potable water piping.

1602.0 Nonpotable Rainwater Catchment Systems. **1602.1 General.
CPC § 102.0 High relevance — show source text
downspouts, and roof washers.|Every 6 months| |Inspect and clear debris from the roof or other aboveground rainwater collection
surface.|Every 6 months| |Remove tree branches and vegetation overhanging roof or other aboveground rain-
water collection surface.|As needed| |Inspect pumps and verify operation.|After initial installation and every 12 months thereafter| |Inspect valves and verify operation.|After initial installation and every 12 months thereafter| |Inspect pressure tanks and verify operation.|After initial installation and every 12 months thereafter| |Clear debris and inspect storage tanks, locking devices, and verify operation.|After initial installation and every 12 months thereafter| |Inspect caution labels and marking.|After initial installation and every 12 months thereafter|

K 102.0 Connection.

K 102.1 General. No water piping supplied by a potable rainwater catchment system shall be connected to a source of supply without the approval of the Authority Having Jurisdiction, Health Department, or other department having jurisdiction.

K 102.2 Connections to Public or Private Potable Water Systems. Potable rainwater catchment systems shall have no direct connection to a public or private potable water supply or alternate water source system. Potable water from a public or private potable water system is permitted to be used as makeup water to the rainwater storage tank provided the public, or private potable water supply connection is protected by an air gap or reduced-pressure principle backflow preventer in accordance with this code. K 102.3 Backflow Prevention. The potable rainwater catchment system shall be protected against backflow in accordance with this code.

K 103.0 Potable Rainfall Catchment System Materials.

K 103.1 Collections Surfaces. The collection surface for potable applications shall be constructed of a hard, impervious material and shall be approved for potable water use. Roof coatings, paints, and liners shall comply with NSF Protocol P151. K 103.1.1 Prohibited. Roof paints and coatings with lead, chromium, or zinc shall not be permitted. Wood roofing material and lead flashing shall not be permitted. K 103.2 Rainwater Catchment System Drainage Materials. Materials used in rainwater catchment drainage systems, including gutters, downspouts, conductors, and leaders shall be in accordance with the requirements of this code for storm drainage.

K 103.3 Storage Tanks. Rainwater storage shall comply with Section K 105.0.

K 103.4 Water Supply and Distribution Materials. Potable rainwater supply and distribution materials shall comply with the requirements of this code for potable water supply and distribution systems.

K 104.0 Design and Installation.

K 104.1 Collection Surfaces. Rainwater shall be collected from a roof or other cleanable aboveground surfaces specifically designed for rainwater catchment. A rainwater catchment system shall not collect rainwater from:

(1) Vehicular parking surfaces

(2) Surface water runoff

(3) Bodies of standing water

K 104.2 Prohibited Discharges. Overflows, condensate, and bleed-off pipes from roof-mounted equipment and appliances shall not discharge onto roof surfaces that are intended to collect rainwater.
CPC § 1603.13 High relevance — show source text
1603.13 Pumps. Pumps serving rainwater catchment systems shall be listed. Pumps supplying water to water closets, urinals, and trap primers shall be capable of delivering not

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NONPOTABLE RAINWATER CATCHMENT SYSTEMS

CAUTION NONPOTABLE RAINWATER, DO NOT DRINK. DO NOT CONNECT TO DRINKING WATER

SYSTEM. NOTICE: CONTACT BUILDING MANAGE MENT BEFORE PERFORMING ANY WORK ON THIS

WATER SYSTEM.

This sign shall be posted in a location that is visible to anyone working on or near rainwater equipment.

1605.0 Inspection and Testing. 1605.1 General. Rainwater catchment systems shall be inspected and tested in accordance with Section 1605.2 and Section 1605.3.

1605.2 Supply System Inspection and Test. Rainwater catchment systems shall be inspected and tested in accordance with the applicable provisions of this code for testing of potable water and storm drainage systems. Storage tanks shall be filled with water to the overflow opening for a period of 24 hours, and during the inspection, or by other means as approved by the Authority Having Jurisdiction. Seams and joints shall be exposed during the inspection and checked for watertightness. 1605.3 Cross-Connection Inspection and Testing. An initial visual inspection and an initial cross-connection test shall be performed on both the potable and rainwater catchment water systems before the initial operation of the rain- water catchment system. During an initial or subsequent cross-connection test, the potable and rainwater catchment water systems shall be isolated from each other and independently inspected and tested to ensure there is no crossconnection in accordance with Section 1602.5. Initial or subsequent inspections or tests shall be performed in accordance with Section 1605.3.1 through Section 1605.3.3 . 1605.3.1 Visual System Inspection. Prior to commencing the cross-connection testing, a dual system inspection shall be conducted by the Authority Having Jurisdiction and other authorities having jurisdiction as follows:

(1) Pumps, equipment, equipment room signs, and exposed piping in an equipment room shall be checked.

1605.3.2 Cross-Connection Test. A cross-connec- tion test shall be performed 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 rainwater catchment water system shall be shut down and completely drained.

(2) The potable water system shall remain pressurized for a minimum period of time specified by the Authority Having Jurisdiction while the rainwater catchment water system is empty. The minimum period the rainwater catchment water system is to remain depressurized shall be determined on a caseby-case basis, taking into account the size and complexity of the potable and rainwater catchment water distribution systems, but in no case shall that period be less than 1 hour.

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CPC § 101.8 High relevance — show source text

K 101.8 Material Compatibility. In addition to the requirements of this appendix, potable rainwater catchment systems shall be constructed of materials that are compatible with the type of pipe and fitting materials and water conditions in the system.

K 101.9 System Controls. Controls for pumps, valves, and other devices that contain mercury that come in contact with the water supply shall not be permitted.

2025 CALIFORNIA PLUMBING CODE 493

APPENDIX K

TABLE K 101.5.1 MINIMUM POTABLE RAINWATER CATCHMENT SYSTEM TESTING, INSPECTION, AND MAINTENANCE FREQUENCY

DESCRIPTION	MINIMUM FREQUENCY
Inspect and clean filters and screens, and replace (where necessary).	Every 3 months
Inspect and verify that disinfection, filters and water quality treatment devices and systems are operational. Perform water quality tests in accordance with the Author- ity Having Jurisdiction.	In accordance with the manufacturer’s instructions, and the Authority Having Jurisdiction.
Perform applicable water quality tests to verify compliance with Section K 104.3.	Every 3 months
Perform a water quality test for E. Coli, Total Coliform, and Heterotrophic bacte- ria. For a system where 25 different people consume water from the system over a 60 day period, a water quality test for cryptosporidium shall be performed.	After initial installation and every 12 months thereafter, or as directed by the Authority Having Jurisdiction.
Inspect and clear debris from rainwater gutters, downspouts, and roof washers.	Every 6 months
Inspect and clear debris from the roof or other aboveground rainwater collection surface.	Every 6 months
Remove tree branches and vegetation overhanging roof or other aboveground rain- water collection surface.	As needed
Inspect pumps and verify operation.	After initial installation and every 12 months thereafter
Inspect valves and verify operation.	After initial installation and every 12 months thereafter
Inspect pressure tanks and verify operation.	After initial installation and every 12 months thereafter
Clear debris and inspect storage tanks, locking devices, and verify operation.	After initial installation and every 12 months thereafter
Inspect caution labels and marking.	After initial installation and every 12 months thereafter

K 102.0 Connection.

K 102.1 General. No water piping supplied by a potable rainwater catchment system shall be connected to a source of supply without the approval of the Authority Having Jurisdiction, Health Department, or other department having jurisdiction.

K 102.2 Connections to Public or Private Potable Water Systems. Potable rainwater catchment systems shall have no direct connection to a public or private potable water supply or alternate water source system. Potable water from a public or private potable water system is permitted to be used as makeup water to the rainwater storage tank provided the public, or private potable water supply connection is protected by an air gap or reduced-pressure principle backflow preventer in accordance with this code. K 102.3 Backflow Prevention. The potable rainwater catchment system shall be protected against backflow in accordance with this code.

K 103.0 Potable Rainfall Catchment System Materials.

CPC § 303.1 High relevance — show source text
2025 CALIFORNIA GREEN BUILDING STANDARDS CODE APPENDIX A4-11

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

APPENDIX A4-12 2025 CALIFORNIA GREEN BUILDING STANDARDS CODE

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

A4 RESIDENTIAL VOLUNTARY MEASURES

DIVISION A4.3 – WATER EFFICIENCY AND CONSERVATION

SECTION A4.301—GENERAL (RESERVED)

SECTION A4.302—DEFINITIONS (RESERVED)

SECTION A4.303—INDOOR WATER USE

A4.303.1 Kitchen faucets. The maximum flow rate of kitchen faucets shall not exceed 1.5 gallons per minute at 60 psi. Kitchen faucets may temporarily increase the flow above the maximum rate, but not to exceed 2.2 gallons per minute at 60 psi, and must default to a maximum flow rate of 1.5 gallons per minute at 60 psi.

Note: Where complying faucets are unavailable, aerators or other means may be used to achieve reduction.

A4.303.2 Alternate water sources for nonpotable applications. Alternate nonpotable water sources are used for indoor potable water reduction. Alternate nonpotable water sources shall be installed in accordance with the California Plumbing Code.

A4.303.3 Appliances. Install at least one qualified ENERGY STAR dishwasher or clothes washer.

Note: See Section A5.303.3 for nonresidential dishwashers and clothes washers.

A4.303.4 Nonwater urinals and waterless toilets. Nonwater urinals or composting toilets are installed.

Where approved, nonwater urinals with drain cleansing action (formerly hybrid urinals), as defined in Chapter 2, shall be considered nonwater urinals.

A4.303.5 Hot water recirculation systems. One- and two-family dwellings shall be equipped with a demand hot water recirculation system, as defined in Chapter 2. The demand hot water recirculation system shall be installed in accordance with the California Plumbing Code, California Energy Code and the manufacturer’s installation instructions.

SECTION A4.304—OUTDOOR WATER USE

A4.304.1 Rainwater catchment systems. An approved rainwater catchment system is designed and installed to use rainwater generated by at least 65 percent of the available roof area. Rainwater catchment systems shall be designed and installed in accordance with the California Plumbing Code.

A4.304.2 Potable water elimination. When landscaping is provided and as allowed by local ordinance, a water efficient landscape irrigation design that eliminates the use of potable water beyond the initial requirements for plant installation and establishment shall be provided. Methods used to accomplish the requirements of this section shall comply with the requirements of the California Building Standards Code and shall include, but not be limited to, the following:
1. Use of captured rainwater.
2. Use of recycled water.
3. Water treated for irrigation purposes and conveyed by a water district or public entity.
4. Use of graywater.
5. Use of drought tolerant plants.
A4.304.3 Landscape water meters. For new water service connections, landscaped irrigated areas less than 5,000 square feet shall be provided with separate submeters or metering devices for outdoor potable water use.
CPC § 4.2.1 High relevance — show source text
1101.4.2.1, 1104.4.2.2

AIR GAPS

Backflow prevention . . . . . . 603.2, Table 603.2, 603.3.1, Table 603.3.1, 603.4.4

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203.0

Discharge from drinking

water treatment units . . . . . . . . . . . . . . . . . . . . . 611.2

AIR TANK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .710.11

ALTERATIONS AND REPAIRS

Fuel gas piping . . . . . . . . . . . .1203.1, 1213.1.2, 1213.4.2

Health care facilities . . . . . . . . . . . . . . . . . . . . . . .1301.5

Plumbing systems . . . . . . . . . . . . . . . . . .102.4, 301.2.5 ALTERNATE MATERIALS, DESIGN,

AND METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . .301.3

ALTERNATE WATER SOURCE

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203.0

For nonpotable applications . . .Chapter 15, Chapter 16 For special water features . . . . . . . . . . . . . . . . .L 406.1

Future connections . . . . . . . . . . . . . . . . . . . . .1504.9.1

Identification of piping . . . . . . . . . . . . . . . . . . . . .601.3.3 Nonpotable rainwater catchment system . . . . . . . . . . .Table 1601.5, 1602.4

Potable rainwater

catchment system . . . . . . . . . . . . . . . . . . . . . .K 102.2 ANODELESS RISER, DEFINITION . . . . . . . . . . . . . . .203.0

APPLIANCES

Automatically operated . . . . . . . . . . . .509.3.4, 509.5.7.1 Categorized vent diameter/area, definition . . . . . . . . . . . . . . . . . .203.0 Connections to building fuel gas piping . . . . . . . . . . . . . . . . . . . . . . . . .1212.0

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203.0

Direct-vent . . . . . . . . . . . . . . . .206.0, 509.2.6, 509.5.10.1,

509.8.1, 509.12

2025 CALIFORNIA PLUMBING CODE 563
CPC § 1701.1 High relevance — show source text
Chapter 16 Nonpotable Rainwater Catchment Systems.

Chapter 16 regulates nonpotable rainwater catchment systems that include irrigation; toilet and urinal flushing with proper treatment; provisions where permits are required; maintenance of alternate water sources; and minimum water quality. This chapter provides guidance on how to optimize rainwater use while ensuring there is a decrease of risk to consumers from poor design, installation, and maintenance. Rainwater harvesting is the process of capturing, channeling, and storing water runoff for later use. Most systems are constructed of three principal components: the catchment area, the collection device, and the conveyance system.

Chapter 17 Referenced Standards.

Chapter 17 provides two comprehensive tables with referenced standards. The standards listed in Table 1701.1 are applied as indicated in the applicable reference section(s). A list of additional approved standards, publications, practices, and guides that are not referenced in specific sections appear in Table 1701.2.

Referenced standards set forth specific details of accepted practices, materials specifications, or test methods in many specialized applications. Standards provide an efficient method of conveying complex information and specifications on the performance requirements for materials, products, systems, application, and installation. The manner and purpose for a standard’s use and, in turn, code compliance, must be definitive in all references to the standard. If the standard is intended to be a requirement for judging code compliance, the code must state its intent for use. The standard should adequately address a defined need and at the same time specify the minimum performance requirements, technical characteristics and methods of testing, and required test results.

The referenced standards tables are organized in a manner that makes it easy to find specific standards in alphabetical order, and by acronym of the publishing agency of the standard. The tables list the title of the standard, the edition, and any addenda. Contact information for each publishing agency is provided at the end of the chapter.

Appendix A Recommended Rules for Sizing the Water Supply System.

Appendix A provides a method of sizing the water supply and distribution system that provides precise calculations to establish the proper pressures and flow to the system’s fixtures. The goal of sizing the system is to deliver an acceptable volume of water to the most hydraulically remote fixture during minimum pressure and maximum flow conditions; provide satisfactory water pressure to the most hydraulically remote fixture during minimum pressure and maximum flow conditions; and to prevent excessive water velocity during maximum flow conditions.

Appendix B Explanatory Notes on Combination Waste and Vent Systems.

Appendix B contains general guidelines for the design and installation of combination waste and vent systems. These systems are designed for waste piping and are purposely oversized to serve as both a waste and vent pipe to avoid excessive pneumatic effects at fixture drains.

Appendix C Alternate Plumbing Systems.

The intent of this appendix is to provide clarification of procedures for the design and approval of engineered plumbing systems, alternate materials, and equipment that are not specifically covered in other parts of the code. Alternative methods are allowed to be used where approved by the authority having jurisdiction. Approval of alternatives is based on a demonstration showing that the method or material used is at least equivalent in strength, deflection, and capacity to that provided by the prescriptive methods and materials.

Appendix D Sizing Storm Water Drainage Systems.

Appendix D provides general guidelines for the sizing of stormwater drainage systems. There are two pieces of information that must always be a given. They are the roof size and the rate of rainfall f

Frequently asked questions

Can I pipe harvested rainwater directly into my house drinking water lines?

No — the CPC prohibits direct connections between rainwater catchment systems and potable water supplies. Makeup potable water is only allowed through an air gap or approved backflow protection, and any potable‑grade rainwater system must be approved by the AHJ. See § 1602.4 and § K 102.2.

May I temporarily connect the potable supply to my rainwater tank for commissioning?

Yes — a temporary potable connection is permitted only for the initial cross‑connection test and must be disconnected when the test is complete. See § 1602.4 (Exception 2) and the cross‑connection testing sections.

How long must the potable system remain depressurized during cross‑connection testing?

The AHJ sets the required time based on system size and complexity, but it shall be not less than 1 hour. See § 1605.3.2.

Do I need special materials if I plan to use harvested rainwater for potable uses?

Yes — potable rainwater systems must use materials and collection surfaces approved for potable use (hard, impervious, NSF Protocol P151 where applicable) and follow Appendix K design/maintenance rules where adopted. See § K 103.1 and § K 101.4.

How must gutters and downspouts be sized for a rainwater system?

Gutters, leaders and downspouts must be sized in accordance with Chapter 11 of the CPC; the rainwater chapter requires that sizing comply with Chapter 11. See § 1602.6.

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