CPC · California Plumbing Code

What minimum water quality/treatment is required for intended uses?

If you plan to use harvested rainwater for anything but potable uses, the local Authority Having Jurisdiction sets the required water quality; if they haven’t set requirements the California Plumbing Code’s Table 1603.4 gives defaults — typically debris control, a **100‑micron** filter for toilets/urinals and drip irrigation, and numeric targets for **E. coli (<100 CFU/100 mL)** and **turbidity (<10 NTU)** where specified. Follow the Table, apply disinfection when needed, and test/maintain the system at least annually.

Ask a question free See coverage

Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

The California Plumbing Code says the minimum water quality for rainwater catchment systems must meet the water-quality requirements for the intended application as determined by the Authority Having Jurisdiction — and specifically points nonpotable systems to § 1603.4 for required treatments and water-quality metrics. § 1601.7 explains that where local requirements are absent, the prescriptive defaults in Table 1603.4 apply.

The single most important rule: use the water-quality standard required for the intended end use (local AHJ decides); if the AHJ has no rule, follow Table 1603.4.

Requirements in detail

Scope and decision process

  • The starting point is the application (e.g., toilet/urinal flushing, spray irrigation, drip irrigation, car washing, cooling-tower make‑up, ornamental fountains, etc.). The AHJ determines applicable water-quality requirements; absent local rules, follow Table 1603.4. § 1601.7 and § 1603.4 (and Table 1603.4) are the controlling provisions.

  • Where disinfection is required, disinfection must be applied so the required quality is delivered at the point of use; chlorine residual testing (if chlorine used) is governed by ASTM D1253 and local limits. See § 1603.4.1 for disinfection direction.

Key required devices and minimum physical treatments

  • A debris excluder or other approved means is required in many applications (see Table 1603.4).
  • A filter permitting passage ≤ 100 microns (100 µm) is specifically required for water supplied to water closets, urinals, trap primers, and drip irrigation. § 1603.18 establishes the 100 µm requirement.
  • Water-quality devices and treatment equipment must be listed/labeled (third‑party certified) and approved for the intended application. § 1603.15 covers device listing/approval.

Prescriptive values from Table 1603.4

The table below condenses the decision‑critical dimensions and thresholds from Table 1603.4 into a quick-reference format.

Application (decision) Minimum treatment required Minimum water-quality target (if specified) Code reference
Car washing Debris excluder / approved means; 100 µm filter for drip irrigation only N/A Table 1603.4 — § 1603.4
Surface, subsurface, and drip irrigation Debris excluder / approved means; 100 µm filter for drip irrigation N/A Table 1603.4 — § 1603.4
Spray irrigation — max storage < 360 gallons (1363 L) Debris excluder / approved means; disinfection per § 1603.4.1 N/A Table 1603.4 — § 1603.4
Spray irrigation — max storage ≥ 360 gallons (1363 L) Debris excluder / approved means E. coli: < 100 CFU/100 mL; Turbidity: < 10 NTU Table 1603.4 — § 1603.4
Urinal & water-closet flushing; clothes washing; trap-priming Debris excluder / approved means; 100 µm filter E. coli: < 100 CFU/100 mL; Turbidity: < 10 NTU Table 1603.4 & § 1603.18 — § 1603.4
Ornamental fountains / water features Debris excluder / approved means E. coli: < 100 CFU/100 mL; Turbidity: < 10 NTU Table 1603.4 — § 1603.4
Cooling-tower make-up Debris excluder / approved means; 100 µm where noted E. coli: < 100 CFU/100 mL; Turbidity: < 10 NTU Table 1603.4 — § 1603.4

Notes:

  • The table above reproduces the CPC’s prescriptive defaults used when local AHJ requirements are absent; always confirm whether the AHJ has different or additional requirements. § 1601.7 directs you to follow AHJ requirements first, and to Table 1603.4 only when the AHJ has not set requirements.
  • The numeric water-quality thresholds shown in the table (E. coli and turbidity limits) come directly from Table 1603.4.

Monitoring, testing and maintenance

  • Systems required to meet § 1603.4 water quality must be tested to maintain that quality. Table 1601.5 sets minimum testing/inspection frequencies — for example, water-quality tests required by § 1603.4 are to be performed every 12 months (and after renovation/repair) per Table 1601.5.
  • If chlorine is used for disinfection, residual chlorine must be tested in accordance with ASTM D1253 and must not exceed levels allowed for the intended use (as required by local enforcing agency). See § 1603.4.1.

Exceptions & special cases

  • No water treatment is required for rainwater systems used for aboveground irrigation with a maximum storage capacity of 360 gallons (1363 L). § 1601.7 Exception (1).
  • No treatment is required for rainwater used for surface, subsurface, or drip irrigation (this exception is in § 1601.7 Exception (2)), though Table 1603.4 still lists basic debris control/filtration where applicable.
  • For applications with AHJ-determined or local public‑health requirements (for example, potable reuse within a private building or public potable systems), follow the AHJ’s standards — the CPC defers to the AHJ and other statutes/regulations (e.g., Title 22 for recycled water where applicable). § 1601.7 and adjacent sections explain this interplay.

Common mistakes

  • Assuming Table 1603.4 is optional: Table 1603.4 is the CPC default when the Authority Having Jurisdiction has not set a requirement; don’t skip it. § 1601.7.
  • Skipping the 100 µm filter requirement for water closets/urinals/drip irrigation — § 1603.18 explicitly requires it.
  • Treating “N/A” cells (no numeric target) as “no care required.” Even where Table 1603.4 shows N/A for numeric limits, physical controls (debris excluder, filters) and AHJ direction still apply.
  • Using chlorine without testing residuals or without verifying local allowable residual levels — § 1603.4.1 and ASTM D1253 apply.
  • Forgetting required maintenance/testing frequency — water-quality tests for systems that must meet § 1603.4 are listed under Table 1601.5 (minimum once every 12 months).

Worked example — concrete scenario

Scenario: A small office installs a nonpotable rainwater system with a 1,000‑gallon storage tank to supply toilet flushing and drip irrigation.

Step 1 — identify intended uses: toilet flushing (to water closets/urinals) and drip irrigation. The AHJ does not have additional local rules, so apply Table 1603.4 per § 1601.7.

Step 2 — required treatments from Table 1603.4:

  • For toilet flushing: provide a debris excluder and a filter permitting passage ≤ 100 µm; meet E. coli < 100 CFU/100 mL and Turbidity < 10 NTU at point of use.
  • For drip irrigation: provide a debris excluder and the 100 µm filter specified for drip systems (no numeric E. coli/turbidity specified for drip irrigation in the table).

Step 3 — implement disinfection if needed: If initial collection quality or monitoring shows microbial exceedances, apply a disinfection method (chlorination, UV, ozone, etc.) so the point‑of‑use targets are achieved; if chlorine is used, test for residual per ASTM D1253 and meet local allowable residual levels. § 1603.4.1 applies.

Step 4 — testing & maintenance: Test water quality per Table 1601.5 — at a minimum, water-quality testing every 12 months for systems required to meet § 1603.4; inspect filters and clean per manufacturer/AHJ guidance.

Related provisions

  • § 1601.7 — Minimum water quality requirements and when Table 1603.4 applies.
  • § 1603.4 — Minimum water quality for harvested rainwater; reference to Table 1603.4.
  • Table 1603.4 — Prescriptive minimum treatments and numeric targets where specified (E. coli, turbidity).
  • § 1603.4.1 — Disinfection requirements and residual testing if chlorine is used.
  • § 1603.15 — Listing/labeling requirement for water‑quality devices and equipment.
  • § 1603.17 — Debris‑excluder / debris‑removal requirements for collection systems.
  • § 1603.18 — Required 100 µm filter for water closets, urinals, trap primers, and drip irrigation.
  • Table 1601.5 — Minimum testing, inspection, and maintenance frequency (water-quality tests every 12 months for systems required by § 1603.4).

Code references

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

  • 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 § 1603.4 High relevance — show source text

    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| |

    Cross-connection inspection
    and test.*|After initial installation and
    every 12 months thereafter| |



    Test water quality of rainwater
    catchment systems required by
    Section 1603.4 to maintain a
    minimum water quality.|Every 12 months. After system
    renovation or repair.|

    • The cross-connection test shall be performed in the presence of the Authority Having Jurisdiction in accordance with the requirements of this chapter.

    1601.5.1 Maintenance Responsibility. The required maintenance and inspection of rainwater catchment systems shall be the responsibility of the property owner unless otherwise required by the Authority Having Jurisdiction.

    2025 CALIFORNIA PLUMBING CODE 327

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

    NONPOTABLE RAINWATER CATCHMENT SYSTEMS

    1601.6 Operation and Maintenance Manual. An operation and maintenance manual for rainwater catchment systems required to have a permit in accordance with Section 1601.3, shall be supplied to the building owner by the system designer or installer . The operating and maintenance manual shall include the following:

    (1) Diagram(s) of the entire system and the location of system components.

    (2) Instructions for operating and maintaining the system.

    (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.

  • CPC § 1506.0. High relevance — show source text

    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

    exclusively for subsurface landscape irrigation.

    drainage systems, including gutters, downspouts, conductors, and leaders shall be in accordance with the 1603.3.2 Prohibited Discharges. Overflows and requirements of this code for storm drainage. bleed-off pipes from roof-mounted equipment and appli ances shall not discharge onto roof surfaces that are

    1602.7.3 Storage Tanks. Rainwater storage tanks shall

    intended to collect rainwater without prior approval from

    comply with Section 1603.5.

    the Authority Having Jurisdiction.

    1602.8 Rainwater Catchment System Color and

    1603.4 Minimum Water Quality. The minimum water

    Marking Information. Rainwater catchment systems shall

    quality for harvested rainwater shall meet the applicable water

    have a colored background in accordance with Section 601.3.

    quality requirements for the intended applications as deter Rainwater catchment systems shall be marked, in lettering in

    mined by the Authority Having Jurisdiction. In the absence of

    accordance with Section 601.3.3, with the words: “CAU water quality requirements determined by the Authority Hav TION: NONPOTABLE RAINWATER, DO NOT DRINK.”

    ing Jurisdiction, the minimum treatment and water quality

    1602.9 Deactivation and Drainage for Cross-Connec- shall be in accordance with Table 1603.4, IAPMO IGC 324 tion Test. The rainwater catchment system and the potable or NSF/ANSI 350. water system within the building shall be provided with the Exception [BSC] : No treatment is required for rainwater required appurtenances (e.g., valves, air or vacuum relief used for subsurface or nonsprinkled surface irrigation where valves, etc.) to allow for deactivation or drainage as required for the maximum storage volume is less than 5000 gallons (18 a cross-connection test in accordance with Section 1605.3. 927 L) where the tank is supported directly upon grade and the

    ratio of height to diameter or width does not exceed 2 to 1 .

    1603.0 Design and Installation. 1603.4.1 Disinfection. Where the initial quality of the

    collected rainwater requires disinfection or other treat-

    1603.1 Rainwater Catchment Systems. The design and

    ment or both, the collected rainwater shall be treated as

    installation of nonpotable rainwater catchment systems shall

    necessary to ensure the required water quality is deliv-

    be in accordance with Section 1603.2 through Section 1603.20.

    ered at the point of use. Where chlorine is used for dis-

    1603.2 Outside Hose Bibbs. Outside hose bibbs shall be infection or treatment, water shall be tested for residual allowed on rainwater piping systems. Hose bibbs supplying chlorine in accordance with ASTM D1253. The levels of rainwater shall be marked with the words: “CAUTION: residual chlorine shall not exceed the levels allowed for NONPOTABLE RAINWATER, DO NOT DRINK” and in the intended use in accordance with the requirements of Figure 1603.2. the local enforcing agency.

  • CPC § 1601.5 High relevance — show source text

    TABLE 1601.5 MINIMUM ALTERNATE WATER SOURCE 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 and
    maintaining minimum water
    quality requirements as
    determined by the Authority
    Having Jurisdiction.    		 In accordance with manufac-
    turer’s instructions and 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 another above-
    ground rainwater collection
    surfaces.    		 Every 6 months




    Remove tree branches and
    vegetation overhanging a roof
    or other aboveground rainwater
    collection surfaces.    		 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 from 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


    Cross-connection inspection
    and test.*    		 After initial installation and
    every 12 months thereafter




    Test water quality of rainwater
    catchment systems required by
    Section 1603.4 to maintain a
    minimum water quality.    		 Every 12 months. After system
    renovation or repair.
    • The cross-connection test shall be performed in the presence of the Authority Having Jurisdiction in accordance with the requirements of this chapter.

    1601.5.1 Maintenance Responsibility. The required maintenance and inspection of rainwater catchment systems shall be the responsibility of the property owner unless otherwise required by the Authority Having Jurisdiction.

    2025 CALIFORNIA PLUMBING CODE 327

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

    NONPOTABLE RAINWATER CATCHMENT SYSTEMS

    1601.6 Operation and Maintenance Manual. An operation and maintenance manual for rainwater catchment systems required to have a permit in accordance with Section 1601.3, shall be supplied to the building owner by the system designer or installer . The operating and maintenance manual shall include the following:

    (1) Diagram(s) of the entire system and the location of system components.

    (2) Instructions for operating and maintaining the system.

    (3) Instructions on maintaining the required water quality as for rainwater catchment systems .

  • CPC § 104.2 High relevance — show source text

    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.

    K 104.3 Minimum Water Quality. Upon initial system startup, the quality of the water for the intended application shall be verified at the point(s) of use as determined by the Authority Having Jurisdiction in accordance with Section K 104.3.1 and Section K 104.3.2. Water quality maintenance shall be in accordance with Section K 104.3.3.

    K 104.3.1 Private Potable Water System. In the absence of water quality requirements determined by the Authority Having Jurisdiction, the minimum water quality for a private potable water system at the point of use shall comply with Table K 104.3.1.

    494 2025 CALIFORNIA PLUMBING CODE

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

    APPENDIX K

    TABLE K 104.3.1

    MINIMUM WATER QUALITY

    Escherichia coli (fecal coliform) Non-detectable


    Protozoan Cysts    		 Non-detectable

    Viruses    		 Non-detectable
    Turbidity <0.3 NTU

    K 104.3.2 Public Use Occupancies. The minimum water quality for a potable water system for public use occupancies at the point of use and testing procedures shall comply with the Environmental Protection Agency (EPA) Safe Drinking Water Act for a public water sys tem.

    K 104.3.3 Maintenance. Normal system maintenance shall require system testing for Escherichia coli (fecal coliform) and turbidity every 3 months in accordance with Table K 104.3.3. Upon failure of the fecal coliform test, the system shall be re-commissioned involving cleaning, and retesting in accordance with Section K 104.3. Testing for viruses and cysts shall occur once after 3 months of initial operation and once every 12 months thereafter.

    Exception: Upon failure of the virus or cyst test, the tests will be repeated every 3 months until the tests results are negative for two consecutive tests.

    TABLE K 104.3.3

    MINIMUM SYSTEM MAINTENANCE REQUIREMENTS

    Escherichia coli (fecal coliform) Non-detectable

    Turbidity    		 <0.3 NTU

    K 104.4 Water Quality Devices and Equipment. Devices and equipment used to treat rainwater to maintain the minimum water quality requirements determined by the Authority Having Jurisdiction shall be listed or labeled (thirdparty certified) by a listing agency (accredited conformity assessment body) and approved for the intended application.

    K 104.4.1 Filtration Devices. Potable water filters shall comply with NSF/ANSI 53 and shall be installed in accordance with the manufacturer’s installation instructions.

  • CPC § 1501.5.1 High relevance — show source text

    Exception: [DWR] Recycled water supply systems that are within or a part of a building shall comply with Section 1505.16 .

    1501.5.1 Maintenance Responsibility. The required maintenance and inspection of alternate water source systems shall be the responsibility of the property owner unless otherwise required by the Authority Having Jurisdiction.

    1501.6 Operation and Maintenance Manual. [BSC- CG, HCD 1 & DWR] An operation and maintenance manual for gray water, on-site treated nonpotable water , [DWR] and recycled water supply systems required to have a permit in accordance with Section 1501.3, Section 1505.2, and Section 1506.2 shall be supplied to the building owner by the system designer or installer . The operation and maintenance manual shall include the following:

    (1) Diagram(s) of the entire system and the location of system components.

    (2) Instructions for operating and maintaining the system.

    (3) Instructions on maintaining the required water quality for on-site treated nonpotable water systems.

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

    (5) Applicable testing, inspection, and maintenance frequencies in accordance with Section 1501.5 [DWR] or Section 1505.16 as applicable .

    (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.

    1501.7 Minimum Water Quality Requirements. [BSC- CG, HCD 1 & DWR] The minimum water quality for alternate water source systems shall meet the applicable water quality requirements for the intended application as determined by the Authority Having Jurisdiction. In the absence of water quality requirements, for on-site treated nonpotable systems, the water quality requirements of IAPMO IGC 324 or NSF/ANSI 350 shall apply. [BSC-CG & HCD 1] Water quality requirements for on-site treated nonpotable graywa- ter shall comply with this section and Section 1506.10.2.

    Exception s :

    (1) Water treatment is not required for gray water used in a disposal field or for subsurface or subsoil irrigation.

    (2) [DWR] Recycled water shall comply with the water quality requirements of Section 1505.15.

    2025 CALIFORNIA PLUMBING CODE 309

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

    ALTERNATE WATER SOURCES FOR NONPOTABLE APPLICATIONS

    TABLE 1501.5 [BSC-CG] RECOMMENDED MINIMUM ALTERNATE WATER SOURCE TESTING, INSPECTION, AND MAINTENANCE FREQUENCY

    DESCRIPTION MINIMUM FREQUENCY
    Inspect and clean filters and screens, and replace
    (where necessary).    		 In accordance with manufacturer’s instructions, and/or the
    Authority Having Jurisdiction, or every 3 months.
    Inspect and verify that disinfection, filters,
  • CPC § 1506.6 High relevance — show source text

    »

    »

    »

    »

    »

    »

    »

    water pressure in the on-site treated non-potable gray water supply system within the building exceeds 80 psi (552 kPa), a pressure reducing valve reducing the pressure to 80 psi (552 kPa) or less to water outlets in the building shall be installed.

    1506.6 Initial Cross-Connection Test. A cross-connection test is required in accordance with Section 1502.3. 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. 1506.7 On-Site Treated Nonpotable Gray Water Sys- tem Materials. On-site treated nonpotable gray water supply, and distribution system materials shall comply with the requirements of this code for potable water supply and distribution systems unless otherwise provided for in this section.

    1506.8 On-Site Treated Nonpotable Gray Water Devices and Systems. Devices or equipment used to treat on-site treated nonpotable gray water to maintain the minimum water quality requirements determined by the Authority Having Jurisdiction shall be listed and labeled (third-party certified) by a listing agency (accredited conformity assessment body) or approved for the intended application. Devices or equipment used to treat on-site treated nonpotable gray water for use in the water closet and urinal flushing, surface irrigation, and similar applications shall comply with IAPMO IGC 324, NSF/ANSI 350 or approved by the Authority Having Jurisdiction. 1506.9 On-Site Treated Nonpotable Gray Water Sys- tem Color and Marking Information. On-site treated nonpotable gray water systems shall have a colored background and marking information in accordance with Section 601.3 of this code.

    1506.10 Design and Installation. The design and installation of on-site treated nonpotable gray water systems shall be in accordance with Section 1506.10.1 through Section 1506.10.6 .

    1506.10.1 Listing Terms and Installation Instruc- tions. On-site treated nonpotable gray water systems shall be installed in accordance with the terms of its listing and the manufacturer’s installation instructions. 1506.10.2 Minimum Water Quality. [BSC-CG & HCD 1] On-site treated nonpotable gray water supplied to toilets or urinals or for other uses in which it is sprayed or exposed shall be disinfected. Acceptable disinfection methods shall include chlorination, ultraviolet sterilization, ozone, or other methods as approved by the Authority Having Jurisdiction. The minimum water quality for on-site treated nonpotable gray water systems shall meet the applicable water quality requirements for the intended applications as determined by the public health Authority Having Jurisdiction. In the absence of local water quality requirements for on-site treated nonpotable gray water, the requirements of IAPMO IGC 324 or NSF/ANSI 350 shall apply.

    2025 CALIFORNIA PLUMBING CODE 323

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

  • CPC § 1506.9 Medium relevance — show source text

    1506.9 On-Site Treated Nonpotable Gray Water Sys- tem Color and Marking Information. On-site treated nonpotable gray water systems shall have a colored background and marking information in accordance with Section 601.3 of this code.

    1506.10 Design and Installation. The design and installation of on-site treated nonpotable gray water systems shall be in accordance with Section 1506.10.1 through Section 1506.10.6 .

    1506.10.1 Listing Terms and Installation Instruc- tions. On-site treated nonpotable gray water systems shall be installed in accordance with the terms of its listing and the manufacturer’s installation instructions. 1506.10.2 Minimum Water Quality. [BSC-CG & HCD 1] On-site treated nonpotable gray water supplied to toilets or urinals or for other uses in which it is sprayed or exposed shall be disinfected. Acceptable disinfection methods shall include chlorination, ultraviolet sterilization, ozone, or other methods as approved by the Authority Having Jurisdiction. The minimum water quality for on-site treated nonpotable gray water systems shall meet the applicable water quality requirements for the intended applications as determined by the public health Authority Having Jurisdiction. In the absence of local water quality requirements for on-site treated nonpotable gray water, the requirements of IAPMO IGC 324 or NSF/ANSI 350 shall apply.

    2025 CALIFORNIA PLUMBING CODE 323

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

    324 2025 CALIFORNIA PLUMBING CODE

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

    CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE

    CHAPTER 16 - NONPOTABLE RAINWATER CATCHMENT SYSTEMS

    (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.)

    |Adopting Agency
    Adopt Entire Chapter
    Adopt Entire Chapter as
    amended (amended
    sections listed below)
    Adopt only those sections
    that are listed below
    Chapter/Section
    1601.2
    1601.3 & Exceptions 1 & 2
    1601.5
    1601.6
    1601.7
    1602.4 & Exceptions
    1602.7
    1603.3
    1603.3.1 & Exception
    1603.4
    1603.4.1
    Table 1603.4
    1603.7
    1603.8
    1603.9
    1603.10 A & B
    1603.12
    1603.20
    1604.1 - 1604.3
    1605.3
    1605.3.2
    1605.3.

  • CPC § 101.0 Medium relevance — show source text

    2025 CALIFORNIA PLUMBING CODE 547

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

    548 2025 CALIFORNIA PLUMBING CODE

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

    APPENDIX S

    ONSITE STORMWATER TREATMENT SYSTEMS

    The provisions contained in this appendix are not mandatory unless specifically adopted by a state agency, or referenced in the adopting ordinance.

    S 101.0 Onsite Stormwater Treatment Systems. S 101.1 General. The provisions of this appendix shall apply to the water quality, monitoring, design, construction, alteration, repair, and operation requirements of onsite stormwater treatment systems for nonpotable use. S 101.2 Allowable Use of Stormwater. Where approved or required by the Authority Having Jurisdiction, stormwater shall be permitted to be used in lieu of potable water for uses such as, but not limited to, water closets, urinals, clothes washers, ornamental plant irrigation, and dust suppression. S 101.3 Design and Construction Requirements. Onsite stormwater treatment systems shall meet the design, construction, and performance requirements of Section S 101.3.1 or Section S 101.3.2.

    S 101.3.1 Listed Stormwater Treatment Systems. Onsite stormwater treatment systems shall be listed to ARCSA/ASPE 78, installed according to the manufacturer's instructions, and commissioned in accordance with Section S 101.13.

    S 101.3.2 Alternative Design Systems. Where approved by the Authority Having Jurisdiction, onsite stormwater treatment systems for residential and commercial applications shall comply with the provisions of Sections S 101.4 through Section S 101.15. S 101.4 Permit. It shall be unlawful for any person to construct, install, alter, or cause to be constructed, installed, or altered any stormwater treatment system in a building or on a premise without first obtaining a permit to do such work from the Authority Having Jurisdiction. S 101.5 Component Identification. System components shall be properly identified as to the manufacturer. S 101.6 Material Compatibility. Stormwater treatment 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. S 101.7 Log Reduction Targets. Stormwater treatment systems shall be designed to meet the log reduction targets as set forth in Table S 101.7. To meet the log reduction in Table S 101.7, treatment processes used in stormwater systems shall comply with Section S 101.8 for validation or be operated according to conditions approved by the Authority Having Jurisdiction.

    S 101.8 Effluent Water Quality Parameters. Stormwater treatment systems shall be designed to meet the effluent water quality parameters for water closet and urinal fixture use listed in Table S 101.8.

    S 101.9 Validation. Where required by the Authority Having Jurisdiction, treatment processes shall be tested to verify the pathogen reduction performance. The treatment processes shall be validated through third-party component validation or

  • CPC § 3.0 Medium relevance — show source text

    1% FECAL**
    CONTAMINATION CONTRIBUTION2| |

    Ornamental plant irrigation1/
    dust suppression|3.0|2.5|2.0| |
    Indoor use|3.5|3.5|3.0|

    Notes: 1 Non-food. 2 Stormwater can contain some quantity of fecal contamination. The extent of fecal contamination present will depend on site-specific conditions. The appropriate LRT to apply for a stormwater treatment system depend on the site-specific extent of likely contamination of stormwater with fecal contamination.

    TABLE S 101.8

    EFFLUENT WATER QUALITY PARAMETERS FOR WATER

    CLOSET AND URINAL FIXTURE USE

    Col1 MINIMUM MAXIMUM

    Alkalinity mg/L    		 20 200

    TDS mg/L    		 0 500

    Turbidity NTU    		 0 5

    pH    		 6.0 9.0

    Odor    		 Non-Offensive Non-Offensive

    Oily Film and Foam    		 Visual Non-detectable Visual Non-detectable

    Free Chlorine Residual ppm    		 NA 4

    Combined Chlorine ppm    		 NA 4
    Chloramines mg/L NA 4

    S 101.10 Health and Safety. Potable water systems shall be protected against nonpotable water in accordance with Section 602.0 and Section 603.0 of this code.

    TABLE S 101.7 LOG REDUCTION TARGETS FOR 10 [-4] INFECTIONS PER

    PERSON PERYEAR BENCHMARKS FOR STORMWATER

    TREATMENT SYSTEMS

    Notes: 1 Non-food. 2 Stormwater can contain some quantity of fecal contamination. The extent of fecal contamination present will depend on site-specific conditions. The appropriate LRT to apply for a stormwater treatment system depend on the site-specific extent of likely contamination of stormwater with fecal contamination.

    TABLE S 101.8

    EFFLUENT WATER QUALITY PARAMETERS FOR WATER

    CLOSET AND URINAL FIXTURE USE

    2025 CALIFORNIA PLUMBING CODE 549

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

    APPENDIX S

    S 101.11 Monitoring Requirements. Monitoring of stormwater treatment systems shall be based on the risk level in accordance with Table S 101.11(1). The parameters listed in Table S 101.11(2) shall be monitored by sensors placed in the effluent of the system and connected to a smart controller. The smart controller shall activate an alarm when the parameters in Table S 101.11(2) are outside the specifications and shall shut the system down when the alarm is not acknowledged after a period of 8 hours has elapsed. For Category 2, quarterly grab samples shall be taken out of the effluent and analyzed by an accredited lab. The sensors' accuracy and response shall be validated upon commissioning of the system by an independent third party.

    TABLE S 101.11(1)

    RISK LEVELS

  • CPC § 103.0 Medium relevance — show source text

    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.

    K 104.3 Minimum Water Quality. Upon initial system startup, the quality of the water for the intended application shall be verified at the point(s) of use as determined by the Authority Having Jurisdiction in accordance with Section K 104.3.1 and Section K 104.3.2. Water quality maintenance shall be in accordance with Section K 104.3.3.

    K 104.3.1 Private Potable Water System. In the absence of water quality requirements determined by the Authority Having Jurisdiction, the minimum water quality for a private potable water system at the point of use shall comply with Table K 104.3.1.

    494 2025 CALIFORNIA PLUMBING CODE

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

    APPENDIX K

    TABLE K 104.3.1

    MINIMUM WATER QUALITY

    Escherichia coli (fecal coliform) Non-detectable


    Protozoan Cysts    		 Non-detectable

    Viruses    		 Non-detectable
    Turbidity <0.3 NTU

    K 104.3.2 Public Use Occupancies. The minimum water quality for a potable water system for public use occupancies at the point of use and testing procedures shall comply with the Environmental Protection Agency (EPA) Safe Drinking Water Act for a public water sys tem.

  • CPC § 1602.6 Medium relevance — show source text

    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.

    328 2025 CALIFORNIA PLUMBING CODE

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

    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

    exclusively for subsurface landscape irrigation.

    drainage systems, including gutters, downspouts, conductors, and leaders shall be in accordance with the 1603.3.2 Prohibited Discharges. Overflows and requirements of this code for storm drainage. bleed-off pipes from roof-mounted equipment and appli ances shall not discharge onto roof surfaces that are

    1602.7.3 Storage Tanks. Rainwater storage tanks shall

    intended to collect rainwater without prior approval from

    comply with Section 1603.5.

    the Authority Having Jurisdiction.

    1602.8 Rainwater Catchment System Color and

    1603.4 Minimum Water Quality. The minimum water

    Marking Information. Rainwater catchment systems shall

    quality for harvested rainwater shall meet the applicable water

    have a colored background in accordance with Section 601.3.

    quality requirements for the intended applications as deter Rainwater catchment systems shall be marked, in lettering in

    mined by the Authority Having Jurisdiction. In the absence of

    accordance with Section 601.3.3, with the words: “CAU water quality requirements determined by the Authority Hav TION: NONPOTABLE RAINWATER, DO NOT DRINK.”

    ing Jurisdiction, the minimum treatment and water quality

  • CPC § 1603.0 High relevance — show source text

    ratio of height to diameter or width does not exceed 2 to 1 .

    1603.0 Design and Installation. 1603.4.1 Disinfection. Where the initial quality of the

    collected rainwater requires disinfection or other treat-

    1603.1 Rainwater Catchment Systems. The design and

    ment or both, the collected rainwater shall be treated as

    installation of nonpotable rainwater catchment systems shall

    necessary to ensure the required water quality is deliv-

    be in accordance with Section 1603.2 through Section 1603.20.

    ered at the point of use. Where chlorine is used for dis-

    1603.2 Outside Hose Bibbs. Outside hose bibbs shall be infection or treatment, water shall be tested for residual allowed on rainwater piping systems. Hose bibbs supplying chlorine in accordance with ASTM D1253. The levels of rainwater shall be marked with the words: “CAUTION: residual chlorine shall not exceed the levels allowed for NONPOTABLE RAINWATER, DO NOT DRINK” and in the intended use in accordance with the requirements of Figure 1603.2. the local enforcing agency.

    1603.5 Rainwater Storage Tanks. Rainwater storage tanks shall comply with IAPMO/ANSI Z1002 and be installed in accordance with Section 1603.6 through Section 1603.12.

    1603.6 Location. Rainwater storage tanks shall be permitted to be installed above or below grade.

    1603.7 Above Grade. Above grade, storage tanks shall be of an opaque material, approved for aboveground use in direct sunlight or shall be shielded from direct sunlight. Tanks shall be installed in an accessible location to allow for inspection and cleaning. The tank shall be installed on a foundation or platform that is constructed to accommodate loads in accordance with the California Building Code .

    Exception: Tanks may be installed directly on grade in accor- dance with Section 1601.3.

    FIGURE 1603.2 1603.8 Below Grade. Rainwater storage tanks installed below grade shall be structurally designed to withstand antic

    2025 CALIFORNIA PLUMBING CODE 329

    «

    «

    «

    «

    «

    «

    «

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

    NONPOTABLE RAINWATER CATCHMENT SYSTEMS

    »

    TABLE 1603.4

    MINIMUM WATER QUALITY

    APPLICATION MINIMUM TREATMENT MINIMUM WATER
    QUALITY
    Car washing Debris excluder or other
    approved means in
    accordance with Section
    1603.17, and 100
    microns_(100 µm)_in
    accordance with Section
    1603.18 for drip
    irrigation.    		 N/A
    _Surface,_Subsurface
    and drip irrigation    		 Debris excluder or
    other approved means
    in accordance with
    Section 1603.17, and
    100 microns_(100 µm)_
    in accordance with
    Section 1603.18 for
    drip irrigation.
  • CPC § 1505.14.2.1 High relevance — show source text

    (1) Notify the Authority Having Jurisdiction of the cross-connection.

    (2) The reclaimed (recycled) water piping to the building and its premises shall be shut down at the meter, and the reclaimed (recycled) water riser shall be drained.

    (3) Potable water piping to the building and its premises shall be shut down at the meter.

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

    2025 CALIFORNIA PLUMBING CODE 321

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

    ALTERNATE WATER SOURCES FOR NONPOTABLE APPLICATIONS

    (5) The building and its premises shall be retested in accordance with Section 1505.14.2.1 and

    Section 1505.14.2.2.

    (6) The potable water system shall be chlorinated with 50 parts-per-million (ppm) chlorine for 24 hours.

    (7) 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. 1505.14.2.4 Periodic Inspection. Periodic visual inspections of recycled water supply systems shall be required by the recycled water supplier or designee following the procedures in Section 1505.14.2.1. Pursuant to California Code of Regu- lations, Title 22, Section 60316, annual visual inspections shall be required for recycled water sup- ply systems that are within or a part of a building. 1505.15 Minimum Water Quality Requirements for Reclaimed (Recycled) Water. The minimum water qual- ity for reclaimed (recycled) water shall meet the applicable water quality requirements of California Code of Regulations, Title 22, Division 4, Chapter 3 (commencing with Section 60301) for disinfected tertiary recycled water and the appli- cable reclaimed (recycled) water use. The reclaimed (recy- cled) water supplier shall supply water in accordance with permits issued by the State Water Resources Control Board or Regional Water Quality Control Board. 1505.16 Maintenance and Inspection. Recycled water supply systems and components shall be inspected and main- tained in accordance with the manufacturer’s recommendations and/or as required by the Authority Having Jurisdiction. The frequency of testing, inspection, and maintenance shall be in accordance with Table 1505.16. The required inspection and maintenance shall be the responsibility of the property owner, unless otherwise required by the Authority Having Jurisdiction.

    1506.0 On-Site Treated Nonpotable Gray Water Sys- tems.

    1506.1 General. The provisions of this section shall apply to the installation, construction, alteration, and repair of onsite treated nonpotable gray water systems intended to supply uses such as water closets, urinals, trap primers for floor

    drains and floor sinks, above and belowground irrigation, and other uses approved by the Authority Having Jurisdiction.

  • CPC § 1505.16 High relevance — show source text

    **_ The minimum water qual- ity for reclaimed (recycled) water shall meet the applicable water quality requirements of California Code of Regulations, Title 22, Division 4, Chapter 3 (commencing with Section 60301) for disinfected tertiary recycled water and the appli- cable reclaimed (recycled) water use. The reclaimed (recy- cled) water supplier shall supply water in accordance with permits issued by the State Water Resources Control Board or Regional Water Quality Control Board. 1505.16 Maintenance and Inspection. Recycled water supply systems and components shall be inspected and main- tained in accordance with the manufacturer’s recommendations and/or as required by the Authority Having Jurisdiction. The frequency of testing, inspection, and maintenance shall be in accordance with Table 1505.16. The required inspection and maintenance shall be the responsibility of the property owner, unless otherwise required by the Authority Having Jurisdiction.

    1506.0 On-Site Treated Nonpotable Gray Water Sys- tems.

    1506.1 General. The provisions of this section shall apply to the installation, construction, alteration, and repair of onsite treated nonpotable gray water systems intended to supply uses such as water closets, urinals, trap primers for floor

    drains and floor sinks, above and belowground irrigation, and other uses approved by the Authority Having Jurisdiction.

    Other approved nonpotable water sources including swim- ming pool backwash operations, air conditioner condensate, rainwater, cooling tower blow-down water, foundation drainage, steam system condensate, fluid cooler discharge water, food steamer discharge water, combination oven dis- charge water, industrial process water, and fire pump test water may be permitted to be collected for re-use by gray water sys- tems, as approved for the intended application. 1506.2 Plumbing Plan Submission. No permit for an on-site treated nonpotable gray water system shall be issued until complete plumbing plans, with data satisfactory to the Authority Having Jurisdiction, have been submitted and approved. [BSC-CG & HCD 1] Prior to commencing the issuance of permits for indoor gray water systems pursuant to state requirements relating to graywater, a city, county, city and county or other local agency shall seek consultation with the local public health department to ensure that local pub- lic health concerns are addressed in local standards or ordi- nances, or in issuing permits. See California Water Code Section 14877.3.

    1506.3 System Changes. No changes or connections shall be made to either the on-site treated nonpotable gray water system or the potable water system within a site containing an on-site treated nonpotable gray water system without approval by the Authority Having Jurisdiction. 1506.4 Connections to Potable or Recycled Water Supply Systems. On-site treated nonpotable gray water systems shall have no direct connection to a potable water supply or recycled water supply system.

    Exceptions:

    (1) Potable or reclaimed (recycled) water is permitted to be used as makeup water for a non-pressurized storage tank provided the makeup water supply inlet is protected by an air gap in accordance with this code.

  • CPC § 101.5.1 Medium relevance — show source text

    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).

    K 101.7 Minimum Water Quality Requirements. The minimum water quality for potable rainwater catchment systems shall comply with the applicable water quality requirements as determined by the Authority Having Jurisdiction. In the absence of water quality requirements, the guidelines EPA/600/R12/618 contains recommended water reuse guidelines to assist regulatory agencies develop, revise, or expand alternate water source water quality standards.

    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

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

    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.
  • CPC § 1601.3. High relevance — show source text

    Exception: Tanks may be installed directly on grade in accor- dance with Section 1601.3.

    FIGURE 1603.2 1603.8 Below Grade. Rainwater storage tanks installed below grade shall be structurally designed to withstand antic

    2025 CALIFORNIA PLUMBING CODE 329

    «

    «

    «

    «

    «

    «

    «

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

    NONPOTABLE RAINWATER CATCHMENT SYSTEMS

    »

    TABLE 1603.4

    MINIMUM WATER QUALITY

    APPLICATION MINIMUM TREATMENT MINIMUM WATER
    QUALITY
    Car washing Debris excluder or other
    approved means in
    accordance with Section
    1603.17, and 100
    microns_(100 µm)_in
    accordance with Section
    1603.18 for drip
    irrigation.    		 N/A
    _Surface,_Subsurface
    and drip irrigation    		 Debris excluder or
    other approved means
    in accordance with
    Section 1603.17, and
    100 microns_(100 µm)_
    in accordance with
    Section 1603.18 for
    drip irrigation.    		 N/A
    Spray irrigation where
    the maximum storage
    volume is less than
    360 gallons_(1363 L)_    		 Debris excluder or other
    approved means in
    accordance with Section
    1603.17, and disinfec-
    tion in accordance with
    Section 1603.15.    		 N/A
    Spray irrigation where
    the maximum storage
    volume is equal to or
    more than 360 gallons
    (1363 L)    		 Debris excluder or
    other approved means
    in accordance with Sec-
    tion 1603.17.    		 Escherichia
    coli: < 100
    CFU/100 mL,
    and Turbidity:
    < 10 NTU
    Urinal and water
    closet flushing,
    clothes washing, and
    trap priming    		 Debris excluder or other
    approved means in
    accordance with Section
    1603.17, and 100
    microns_(100 µm)_ in
    accordance with Section
    1603.18.    		 Escherichia
    coli: < 100
    CFU/100 mL,
    and Turbidity:
    < 10 NTU
    Ornamental fountains
    and other water
    features    		 Debris excluder or
    other approved means
    in accordance with
    Section 1603.17.    		 Escherichia
    coli: < 100
    CFU/100 mL,
    and Turbidity:
    < 10 NTU
    Cooling tower
    make-up water    		 Debris excluder or other
    approved means in
    accordance with Section
    1603.17, and 100
    microns_(100 µm)_ in
    accordance with Section
    1603.18.    		 Escherichia
    coli: < 100
    CFU/100 mL,
    and Turbidity:
    < 10 NTU

Frequently asked questions

Who decides which water-quality target applies to my system?

The local Authority Having Jurisdiction (AHJ) decides first; if the AHJ has no specific rule for your intended use, follow the CPC defaults in Table 1603.4 per § 1601.7.

Are IAPMO/NSF standards referenced anywhere for treatment equipment?

Yes — the CPC requires devices/equipment to be listed/labeled and references standards (and for some alternate-water systems refers to IAPMO IGC 324 or NSF/ANSI 350 when local requirements are absent). See § 1603.15 and related sections.

Do I always need disinfection for toilet flushing?

Not always — Table 1603.4 requires numeric E. coli and turbidity targets for toilet/urinal flushing; if those targets cannot be met by basic filtration and debris controls, disinfection (chlorination/UV/ozone, etc.) must be used so the point-of-use targets are achieved; disinfection specifics are in § 1603.4.1.

How often must I test the rainwater system?

For systems required to meet § 1603.4, Table 1601.5 requires water-quality testing every 12 months (and after system renovation/repair) as a minimum; the AHJ or manufacturer instructions may require more frequent checks.

If my storage is under 360 gallons, do I need any treatment for irrigation?

If the use is aboveground irrigation and storage ≤ 360 gallons (1363 L), § 1601.7 Exception (1) says water treatment is not required; other irrigation types and conditions are treated differently (see Table 1603.4).

More in California Plumbing Code

Ask about the CPC

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

Start Free Trial

Related in the CPC

What are the rules for pumps, filters and treatment equipment?

How must storage tanks be sited, sized, vented and protected?

Rainwater System Design & Components

California Plumbing Code