CPC · California Plumbing Code

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

Homeowner summary: California’s plumbing rules require rainwater tanks to be approved, placed so they can be inspected and won’t float or fail underground, fitted with properly sized overflows and vents that discharge outdoors (not into the house drainage), screened to keep bugs out, and clearly marked “NONPOTABLE RAINWATER.” Key citations: **§ 1603.5**, **§ 1603.6**, **§ 1603.8**, **§ 1603.12** (see CPC excerpts) .

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Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

In plain English: Rainwater storage tanks must be approved construction, may be installed above or below grade, and must be sited and installed so they are structurally secure, accessible for inspection/cleaning, and protected from contamination and vermin. Venting must be provided when overflow/drainage is not sufficient, sized according to the influent piping and the code, terminate above grade, and must not connect to the sanitary drainage system. These requirements are set out in § 1603.5, § 1603.6, § 1603.8, and § 1603.12 of the California Plumbing Code (CPC) (see and ).

The single most important rule: install approved tanks where they can be inspected/cleaned, structurally supported (especially below grade), provide overflow/drainage, and vent them to outside air sized per the influent pipe — do not connect tank vents to the sanitary drainage system (see § 1603.5, § 1603.8, § 1603.12) .

Requirements in detail

1) Overarching approval and standard

  • Tanks must comply with the referenced standard IAPMO/ANSI Z1002 and be installed in accordance with the CPC provisions for rainwater systems — § 1603.5 (see ).

2) Siting — above grade vs. below grade

  • The code allows installation above or below grade — § 1603.6 (see ).
  • Above-grade tanks must be either opaque, approved for sunlight or shielded from direct sun, be accessible for inspection/cleaning and be placed on a foundation or platform per the California Building Code — § 1603.7 (see ).
  • Below-grade tanks must be structurally designed for anticipated earth or other loads; underground tanks must be ballasted, anchored, or otherwise secured to prevent flotation when empty — § 1603.8 (see ). Appendix K gives prescriptive below-grade details (manholes, cover loads, anchoring) — see K 105.3.2 (Appendix K) for specifics (manhole sizes, 300 psf cover load requirement) .

3) Sizing and hydraulic provisions

  • The CPC requires tanks and associated overflow/drainage be sized so the system can drain, clean, and pass incoming flows; the overflow must be sized to accommodate the rainwater entering the tank and be no smaller than the aggregate cross‑sectional area of inflow pipes — § 1603.9.1 (see ).
  • Appendix guidance for surge tanks and surge/sizing rules for graywater/rainwater systems appears elsewhere in the CPC and Appendix K; where a vent size is prescriptive Appendix K provides a minimum (see Venting below) .

4) Venting

  • Where drainage/overflow piping is not provided or is insufficient, a vent must be installed on each tank. The vent must extend from the top of the tank and terminate not less than 6 inches (152 mm) above grade and must be sized in accordance with the code and based on the size of the influent pipe — § 1603.12 (see ).
  • The vent terminal must be directed downward and must be covered with a mesh screen to prevent entry of vermin and insects; vent pipes shall not be connected to the sanitary drainage system — § 1603.12 (see ).
  • Appendix K gives a prescriptive minimum vent diameter of 1½ inches (40 mm) and (in Appendix K text) suggests a downward-directed terminal with a 3/32 in (2.4 mm) mesh for that Appendix method; the prescriptive Appendix guidance should be reconciled with the mandatory CPC section (1603.12) which specifies a 1/16 in (1.6 mm) mesh in the main text — consult the Authority Having Jurisdiction (AHJ) when Appendix and chapter text differ in mesh size or other optional provisions (see K 105.10 and § 1603.12) .

5) Protection, access, markers and contamination control

  • Openings and access must be protected against insects/birds/rodents; screens on vent, inlet and overflow pipes shall have apertures not greater than 1/16 in (1.6 mm) and access openings larger than 12 inches (305 mm) must be secured against tampering — § 1603.10 (see ).
  • Tanks must be marked with capacity and the phrase “NONPOTABLE RAINWATER”; confined‑space warnings apply where a person can enter — § 1603.11 (see ).
  • Where Appendix K is followed, tanks must be constructed of durable, watertight materials and be protected from sunlight (for above‑grade tanks) or designed for earth loads (below grade) — K 105.2/K 105.3.1/K 105.3.2 (see ).

Decision-relevant dimensions / values (quick reference)

Parameter Required value / test Where to check Code Reference
Tank approval standard IAPMO/ANSI Z1002 Tank specification § 1603.5
Above- vs. below-grade Both permitted (must meet different requirements) Siting plan § 1603.6
Below-grade structural design Designed for anticipated earth/other loads; anchored/ballasted to prevent floatation Structural drawings § 1603.8; K 105.3.2
Holding tank cover load (prescriptive, appendix) ≥ 300 psf for underground tanks Appendix K guidance K 105.3.2
Manhole / service port (below grade, appendix) Manhole ≥ 24 in (610 mm) square or 24 in inside diameter; service ports ≥ 8 in (203 mm) Access detail K 105.3.2
Manhole opening minimum ≥ 20 in (508 mm) diameter, located ≥ 4 in (102 mm) above surrounding grade Access detail K 105.3.2
Primary outlet location (prescriptive appendix) Not less than 4 in (102 mm) above tank bottom or use floating inlet Outlet detail K 105.9
Overflow sizing Not less than aggregate cross‑sectional area of inflow pipes Hydraulic design § 1603.9.1
Access openings locking threshold Access openings > 12 in (305 mm) must be secured/lockable Security § 1603.10
Vent termination height ≥ 6 in (152 mm) above grade Venting § 1603.12
Minimum vent diameter (appendix, prescriptive) ≥ 1½ in (40 mm) (Appendix K) Venting K 105.10
Vent screen aperture (main text) Mesh ≤ 1/16 in (1.6 mm) Venting / contamination control § 1603.12 and § 1603.10

(Notes: Appendix K contains additional prescriptive dimensions (K 105.*). When Appendix text and body text differ, follow the mandatory chapter text unless the AHJ adopts Appendix provisions; always confirm with AHJ.)

Exceptions & special cases

  • The code text permits exceptions in Appendix K (alternative prescriptive guidance) — follow Appendix only where allowed and accepted by the Authority Having Jurisdiction (AHJ) (see K 105.*) .
  • For tank vent screen aperture there is an apparent difference between Appendix K (K 105.10 prescriptive: 3/32 in (2.4 mm) mesh) and the main body (1603.12: 1/16 in (1.6 mm) mesh). Where differences exist, resolve with the AHJ; the mandatory CPC chapter text (1603.12) governs unless the AHJ has adopted Appendix K provisions for your project .
  • Tanks intended for potable service must meet potable‑rated tank approval and AHJ requirements; rainwater tanks used for nonpotable applications require marking and other controls per CPC (see § 1603.11) .

Common mistakes

  • Assuming any vent may be tied into the house sanitary vent system — incorrect: tank vent pipes shall not be connected to the sanitary drainage system (see § 1603.12) .
  • Using inadequate mesh or leaving vents unscreened — the CPC requires mesh to exclude insects/rodents and provides aperture limits in § 1603.10 and § 1603.12 (see ).
  • Failing to size the overflow to equal or exceed the inflow (aggregate) — leads to overflow during storms; the code requires overflow sized to handle inflow (§ 1603.9.1) .
  • Installing below‑grade tanks without anchorage/ballast or without designing covers for earth loads — Appendix K requires ballast/anchoring and cover strength where applicable (see K 105.3.2) .
  • Not providing locked access where required or not marking nonpotable systems — see § 1603.10 and § 1603.11 (see ).

Worked example — concrete scenario

Scenario: A small commercial rainwater cistern collects roof area that produces a peak inflow equivalent to two 3‑inch downspouts (each 3" circular). The system designer chooses a 1,200‑gallon underground tank.

Apply the code rules:

  1. Approval: Use a tank that meets IAPMO/ANSI Z1002 — required by § 1603.5 .
  2. Below-grade design: Design the tank structure for earth loads and provide ballast/anchors so it cannot float when empty; design manhole and access per K 105.3.2 (manhole min 24 in square or 24 in diameter, cover support 300 psf, manhole opening min 20 in diameter located 4 in above surrounding grade) — § 1603.8 and K 105.3.2 .
  3. Overflow sizing: Two 3‑inch inflow pipes have combined cross‑sectional area equal to 2 × area(3 in dia) = 2 × (π×1.5²) ≈ 14.1 in². The overflow outlet must have at least 14.1 in² cross‑sectional area (per § 1603.9.1) — choose a 4‑inch circular overflow (area ≈ 12.57 in²) — NOT sufficient; use a 4‑inch plus a 2‑inch or use a 5‑inch (or two 4‑inch) to exceed 14.1 in². Follow § 1603.9.1 to size overflow to at least the aggregate inflow area .
  4. Venting: If overflow/drainage is judged insufficient as a vent path, provide a vent from the top of the tank that terminates ≥ 6 in above grade, sized per influent pipe (or use Appendix prescriptive min 1½ in vent) and screen the terminal with mesh meeting § 1603.12 (and coordinate Appendix K if used) — see § 1603.12 and K 105.10 .
  5. Access and marking: Provide at least one access opening for inspection; secure access openings > 12 in and permanently mark the tank “NONPOTABLE RAINWATER” per § 1603.10–1603.11 .

Related provisions (CPC and appendices)

  • § 1603.5 — Rainwater Storage Tanks (approval requirement)
  • § 1603.6 — Location (above / below grade allowed)
  • § 1603.8 — Below Grade (structural/anchorage)
  • § 1603.9.1 — Overflow outlet sizing (aggregate inflow area)
  • § 1603.10 — Opening and access protection (screens, lockable access)
  • § 1603.11 — Marking (“NONPOTABLE RAINWATER”)
  • § 1603.12 — Storage Tank Venting (venting, termination height, screen, not connecting to sanitary system)
  • Appendix K (K 105.*) — Prescriptive guidance for construction, below‑grade details, vent diameters, vent terminal screens and testing (useful guidance; consult AHJ)

(If you need, I can extract the exact code snippets and page references your AHJ will expect on plan submittal.)

Code references

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

  • CPC § 1603.9 High relevance — show source text

    ipated earth or other loads. Holding tank covers shall be capable of supporting an earth load of not less than 300 pounds per square foot (lb/ft [2] ) (1465 kg/m [2] ) where the tank is designed for underground installation. Below grade rainwater tanks installed underground shall be provided with manholes. Below grade storage tanks, located outside of the building, shall be provided with either a manhole not less than 24 inches (610 mm) square or a manhole with an inside diameter of not less than 24 inches (610 mm). Service ports in manhole cov- ers shall be not less than 8 inches (203 mm) in diameter. The manhole opening shall be not less than 20 inches (508 mm) in diameter and located not less than 4 inches (102 mm) above

    the surrounding grade. The surrounding grade shall be sloped away from the manhole. Underground tanks shall be ballasted, anchored, or otherwise secured, to prevent the tank from floating out of the ground where empty. The combined weight of the tank and hold down system shall meet or exceed the buoyancy force of the tank.

    1603.9 Drainage and Overflow. Rainwater storage tanks shall be provided with a means of draining and cleaning. The overflow drain shall not be equipped with a shutoff valve. The overflow outlet shall discharge in accordance with this code for storm drainage systems. Where discharging to the storm drainage system, the overflow drain and tank drain shall be protected from backflow of the storm drainage system by a backwater valve or other approved method. Back- water valves shall be installed so that access is provided to the working parts for service and repair.

    1603.9.1 Overflow Outlet Size. The overflow outlet

    shall be sized to accommodate the flow of the rainwater

    entering the tank and not less than the aggregate crosssectional area of inflow pipes.

    1603.10 Opening and Access Protection. Rainwater tank openings shall be protected to prevent the entrance of insects, birds, or rodents into the tank and piping systems .

    Rainwater tank access openings exceeding 12 inches (305 mm) in diameter shall be secured to prevent tampering and unintended entry by either a lockable device or other approved method.

    (A) Animals and Insects. Screens installed on vent pipes, inlets, and overflow pipes shall have an aperture of not greater than [1] ∕ 16 of an inch (1.6 mm) and shall be close fit- ting.

    (B) Human Access. A minimum of one access opening shall be provided to allow inspection and cleaning. Rainwater tank manholes and access openings shall be secured by either a lockable device or other approved method to pre- vent unauthorized access.

    1603.11 Marking. Rainwater tanks shall be permanently marked with the capacity and the language: “NONPOTABLE RAINWATER.” Where openings are provided to allow a person to enter the tank, the opening shall be marked with the following language: “DANGER-CONFINED SPACE.”

  • CPC § 105.3.2 High relevance — show source text

    K 105.3.2 Below Grade. Rainwater storage tanks installed below grade shall be structurally designed to withstand anticipated earth or other loads. Holding tank covers shall be capable of supporting an earth load of not less than 300 pounds per square foot (lb/ft [2] ) (1465 kg/m [2] ) where the tank is designed for underground installation. Below grade rainwater tanks installed underground shall be provided with manholes. The manhole opening shall be not less than 20 inches (508 mm) in diameter and located not less than 4 inches (102 mm) above the surrounding grade. The surrounding grade shall be sloped away from the manhole. Underground tanks shall be ballasted, anchored, or otherwise secured, to prevent the tank from floating out of the ground where empty. The combined weight of the tank and hold down system shall meet or exceed the buoyancy force of the tank. K 105.4 Drainage and Overflow. Rainwater storage tanks shall be provided with a means of draining and cleaning. The overflow drain shall not be equipped with a shutoff valve. The overflow outlet shall discharge in accordance with this code for storm drainage systems. Where discharging to the storm drainage system, the overflow drain shall be protected from backflow of the storm drainage system by a backwater valve or other approved method.

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    APPENDIX K

    K 105.4.1 Overflow Outlet Size. The overflow outlet

    shall be sized to accommodate the flow of the rainwater entering the tank and not less than the aggregate crosssectional area of the inflow pipes. K 105.5 Animals and Insects. Rainwater tank openings to the atmosphere shall be protected to prevent the entrance of insects, birds, or rodents into the tank.

    K 105.6 Human Access. Rainwater tank access openings exceeding 12 inches (305 mm) in diameter shall be secured to prevent tampering and unintended entry by either a lockable device or other approved method. K 105.7 Exposure to Sunlight. Rainwater tank openings shall not be exposed to direct sunlight.

    K 105.8 Inlets. A device or arrangement of fittings shall be installed at the inlet of the tank to prevent rainwater from disturbing sediment as it enters the tank. K 105.9 Primary Tank Outlets. The primary tank outlet shall be located not less than 4 inches (102 mm) above the bottom of the tank, or shall be provided with a floating inlet to draw water from the cistern just below the water surface. K 105.10 Storage Tank Venting. Where venting using drainage or overflow piping is not provided or is considered insufficient, a vent shall be installed on each tank. The vent shall extend from the top of the tank and terminate not less than 6 inches (152 mm) above grade and shall be not less than 1 [1] ⁄ 2 inches (40 mm) in diameter. The vent terminal shall be directed downward and covered with a [3] ⁄ 32 of an inch (2.4 mm) mesh screen to prevent the entry of vermin and insect.

  • CPC § 1503.8.3 High relevance — show source text

    6 = Average number of uses per day

    Note: Cubic feet of capacity and Water Factor are contained in product specifications or are available from the washer manufacturer.

    1503.8.3 Daily Discharge. Gray water systems using tanks shall be designed to minimize the amount of time gray water is held in the tank and shall be sized to dis- tribute the total amount of estimated gray water on a daily basis.

    Exception: Approved on-site treated nonpotable gray

    water systems.

    1503.9 Gray Water System Components. Gray water system components shall comply with Section 1503.9.1 through Section 1503.9.4 .

    [HCD 1] Gray water system components shall comply with this chapter.

    1503.9.1 Surge Tanks. Where installed, surge tanks shall be in accordance with the following:

    (1) Surge tanks shall be constructed of solid, durable materials not subject to excessive corrosion or decay and shall be watertight. Aboveground surge tanks shall be protected from direct sunlight or shall be constructed of UV resistant materials including but not limited to heavily tinted or opaque plastic, fiber- glass, lined metal, concrete and wood. Surge tanks constructed of steel shall be approved by the Authority Having Jurisdiction, provided such tanks are in accordance with approved applicable standards.

    (2) Each surge tank shall be vented in accordance with this code. The vent size shall be determined based on

    the total gray water fixture units as outlined in this code.

    (3) Each surge tank shall have an access opening with lockable gasketed covers or approved equivalent to allow for inspection and cleaning.

    (4) Each surge tank shall have its rated capacity permanently marked on the unit. Also, a sign stating “GRAY WATER SYSTEM, CAUTION DANGER — UNSAFE WATER” shall be permanently marked on the holding tank.

    (5) Each surge tank shall have an overflow drain. The overflow drains shall have permanent connections to the building drain or building sewer, upstream of septic tanks. The overflow drain shall not be equipped with a shutoff valve.

    (6) The overflow drainpipes shall not be less in size than the inlet pipe. Unions or equally effective fittings shall be provided for piping connected to the surge tank.

    (7) Surge tank shall be structurally designed to withstand anticipated earth or other loads. Surge tank covers shall be capable of supporting an earth load of not less than 300 pounds per square foot (lb/ft [2] ) (1465 kg/m [2] ) where the tank is designed for underground installation.

    2025 CALIFORNIA PLUMBING CODE 315

    ), 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

    (8) Where a surge tank is installed underground, the system shall be designed so that the tank overflow will gravity drain to the existing sewer line or septic tank. The tank shall be protected against sewer line backflow by a backwater valve installed in accordance with this code.

    (9) Surge tanks shall be installed on dry, level, wellcompacted soil where underground or on a level 3 inch (76 mm) thick concrete slab or other approved method where aboveground.

  • CPC § 106.2.1 High relevance — show source text

    K 106.2.1 Size. The roof washer shall be sized to direct rainwater containing debris that has accumulated on the collection surface away from the storage tank. ARCSA/ASPE/ANSI 63 contains additional guidance on acceptable methods of sizing roof washers.

    K 106.2.2 Debris Screen. The inlet to the roof washer shall be provided with a debris screen or other approved means that protects the roof washer from the intrusion of debris and vermin. Where the debris screen is installed, the debris screen shall be corrosion resistant and shall have openings not larger than [1] ⁄ 2 of an inch (12.7 mm). K 106.2.3 Drain Discharge. Water drained from the roof washer, or pre-filter shall be diverted away from the storage tank and discharged to a disposal area that does not cause property damage or erosion. Roof washer drainage shall not drain over a public way. K 106.2.4 Automatic Drain. Roof washing systems shall be provided with an automatic means of self-draining between rain events.

    K 106.3 Roof Gutters. Gutters shall maintain a minimum slope and be sized in accordance with this code. K 106.4 Drains, Conductors, and Leaders. The design and size of rainwater drains, conductors, and leaders shall comply with this code. K 106.5 Size of Potable Water Piping. Potable rainwater system distribution piping shall be sized in accordance with this code for sizing potable water piping.

    K 107.0 Cleaning. K 107.1 General. The interior surfaces of tanks and equipment shall be clean before they are put into service.

    K 108.0 Supply System Inspection and Test. K 108.1 General. 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 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 water tightness.

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    CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE

    APPENDIX L - SUSTAINABLE PRACTICES

    (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 § 710.11 High relevance — show source text

    Where the preceding requirements are met and the vent, after leaving the sump, is combined with vents from fixtures discharging into the sump, the size of the combined vent need not exceed that required for the total number of fixtures discharging into the sump. No vent from an air-operating sewage ejector shall combine with other vents. 710.11 Air Tanks. Air tanks shall be so proportioned as to be of equal cubical capacity to the ejectors connected in addition to that in which there shall be maintained an air pressure of not less than 2 pounds per foot (lb/ft) (3 kg/m) of height the sewage is to be raised. No water-operated ejectors shall be permitted. 710.12 Grinder Pump Ejector. Grinder pumps shall be permitted to be used. 710.12.1 Discharge Piping. The discharge piping shall be sized in accordance with the manufacturer’s installation instructions and shall be not less than 1 [1] ⁄ 4 inches (32 mm) in diameter. A check valve and fullwaytype shutoff valve shall be located on the discharge line. 710.13 Macerating Toilet Systems and Pumped Waste Systems. Fixtures shall be permitted to discharge to a macerating toilet system, or pumped waste system shall be permitted as an alternate to a sewage pump system where approved by the Authority Having Jurisdiction. Such systems shall comply with ASME A112.3.4/CSA B45.9 and shall be installed in accordance with the manufacturer’s installation

    instructions.

    710.13.1 Sumps. The sump shall be watertight and gastight. 710.13.2 Discharge Piping. The discharge piping shall be sized in accordance with manufacturer’s instructions and shall be not less than [3] ⁄ 4 of an inch (20 mm) in diameter. The developed length of the discharge piping shall not exceed the manufacturer’s instructions. A check

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    SANITARY DRAINAGE

    valve and fullway-type shutoff valve shall be located within the discharge line or internally within the device.

    710.13.3 Venting. The plumbing fixtures that discharge into the macerating device shall be vented in accordance with this code. The sump shall be vented in accordance with the manufacturer’s instructions, and such vent shall be permitted to connect to the fixture venting.

    711.0 Suds Relief.

    711.1 General. Drainage connections shall not be made into a drainage piping system within 8 feet (2438 mm) of a vertical to horizontal change of direction of a stack containing suds-producing fixtures. Bathtubs, laundries, washing machine standpipes, kitchen sinks, and dishwashers shall be considered suds-producing fixtures. Where parallel vent stacks are required, they shall connect to the drainage stack at a point 8 feet (2438 mm) above the lowest point of the drainage stack.

    Exceptions:

    (1) Single-family residences.

    (2) Stacks receiving the discharge from less than three stories of plumbing fixtures.

    712.0 Testing.

  • CPC § 105.5 High relevance — show source text

    shall be sized to accommodate the flow of the rainwater entering the tank and not less than the aggregate crosssectional area of the inflow pipes. K 105.5 Animals and Insects. Rainwater tank openings to the atmosphere shall be protected to prevent the entrance of insects, birds, or rodents into the tank.

    K 105.6 Human Access. Rainwater tank access openings exceeding 12 inches (305 mm) in diameter shall be secured to prevent tampering and unintended entry by either a lockable device or other approved method. K 105.7 Exposure to Sunlight. Rainwater tank openings shall not be exposed to direct sunlight.

    K 105.8 Inlets. A device or arrangement of fittings shall be installed at the inlet of the tank to prevent rainwater from disturbing sediment as it enters the tank. K 105.9 Primary Tank Outlets. The primary tank outlet shall be located not less than 4 inches (102 mm) above the bottom of the tank, or shall be provided with a floating inlet to draw water from the cistern just below the water surface. K 105.10 Storage Tank Venting. Where venting using drainage or overflow piping is not provided or is considered insufficient, a vent shall be installed on each tank. The vent shall extend from the top of the tank and terminate not less than 6 inches (152 mm) above grade and shall be not less than 1 [1] ⁄ 2 inches (40 mm) in diameter. The vent terminal shall be directed downward and covered with a [3] ⁄ 32 of an inch (2.4 mm) mesh screen to prevent the entry of vermin and insect.

    K 105.11 Pumps. Pumps serving rainwater catchment systems shall be listed for potable water use. Pumps supplying water to water closets, urinals, and trap primers shall be capable of delivering not less than the minimum residual pressure required by the highest and most remote outlet served. Where the water pressure in the rainwater 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 in accordance with this code.

    K 105.12 Roof Drains. Primary and secondary roof drains, conductors, leaders, overflows, and gutters shall be designed and installed in accordance with this code.

    K 106.0 Freeze Protection.

    K 106.1 General. Tanks and piping installed in locations subject to freezing shall be provided with an approved means of freeze protection. K 106.2 Roof Washer or Pre-Filtration System. Collected rainwater shall pass through a roof washer or pre-filtration system before the water enters the rainwater storage tank. Roof washer systems shall comply with Section K 106.2.1 through Section K 106.2.4.

    K 106.2.1 Size. The roof washer shall be sized to direct rainwater containing debris that has accumulated on the collection surface away from the storage tank. ARCSA/ASPE/ANSI 63 contains additional guidance on acceptable methods of sizing roof washers.

  • CPC § 608.3 High relevance — show source text

    The expansion tank shall be properly sized, securely fastened to the structure, and installed in accordance with the manufacturer’s installation instructions and listing. Systems designed by a licensed plumbing contractor or registered design professionals shall be permitted to use approved pressure relief valves in lieu of expansion tanks provided such relief valves have a maximum pressure relief setting of 100 psi (689 kPa) or less. 608.3 Expansion Tanks, and Combination Tempera- ture and Pressure-Relief Valves. A water system provided with a check valve, backflow preventer, or other normally closed device that prevents dissipation of building pressure back into the water main, independent of the type of water heater used, shall be provided with an approved, listed, and adequately sized expansion tank or other approved device having a similar function to control thermal expansion. Prepressurized water expansion tanks shall comply with IAPMO/ANSI Z1088. Such expansion tank or other approved device shall be installed on the building side of the check valve, backflow preventer, or other device and shall be sized, securely fastened to the structure, and installed in accordance with the manufacturer’s installation instructions.

    A water system containing storage water heating equipment shall be provided with an approved, listed, adequately sized combination temperature and pressure-relief valve, except for listed nonstorage instantaneous heaters having an inside diameter of not more than 3 inches (80 mm). Each such approved combination temperature and pressure-relief valve shall be installed on the water-heating device in an approved location based on its listing requirements and the manufacturer’s installation instructions. Each such combination temperature and pressure-relief valve shall be provided with a drain in accordance with Section 608.5.

    Exception: An expansion tank shall not be required for an instantaneous non-storage water heater. 608.4 Pressure Relief Valves. Each pressure relief valve shall be an approved automatic type with drain, and each such relief valve shall be set at a pressure of not more than 150 psi (1034 kPa). No shutoff valve shall be installed between the relief valve and the system. 608.5 Discharge Piping. The discharge piping serving a temperature relief valve, pressure relief valve, or combination of both shall have no valves, obstructions, or means of isolation and be provided with the following:

    (1) Not less than the size of the valve outlet and shall discharge full size to the flood level of the area receiving the discharge and pointing down.

    (2) Materials shall be rated at not less than the operating temperature of the system and approved for such use or shall comply with ASME A112.4.1.

    (3) Discharge pipe shall discharge independently by gravity through an air gap into the drainage system or outside of the building with the end of the pipe not exceeding 2 feet

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    WATER SUPPLY AND DISTRIBUTION

    (610 mm) and not less than 6 inches (152 mm) above the ground and pointing downwards.

    (4) Discharge in such a manner that does not cause personal injury or structural damage. (5) No part of such discharge pipe shall be trapped or subject to freezing. (6) The terminal end of the pipe shall not be threaded. (7) Discharge from a relief valve into a water heater pan shall be prohibited. (8) The discharge termination point shall be readily observable.

  • CPC § 502.0 High relevance — show source text

    APPENDIX E

    E 502.0 Recreational Vehicle Park Potable Water Supply and Distribution. E 502.1 Quality. The supply or supplies of water shall comply with the potable water standards of the state, local health authority or, in the absence thereof, with the Drinking Water Standard of the Federal Environmental Protection Agency. E 502.2 Sources. Water approved by a regulating agency shall be acceptable. Where an approved public water supply system is available, it shall be used. Where the park has its own water supply system, the components of the system shall be approved. A water supply system that is used on a seasonal basis shall be provided with means for draining. E 502.3 Prohibited Connections. The potable water supply shall not be connected to a nonpotable or unapproved water supply, nor be subjected to backflow or backsiphonage. E 502.4 Supply. The water supply system shall be designed and constructed in accordance with the following:

    (1) A minimum of 25 gallons (95 L) per day per site for sites without individual water connections.

    (2) A minimum of 50 gallons (189 L) per day per site for sites with individual water connections.

    (3) A minimum of 50 gallons (189 L) per day per site where water-supplied water closets are provided in restrooms.

    E 502.5 Pressure and Volume. Where water is distributed under pressure to an individual site, the water supply system shall be designed to provide a minimum flow pressure of not less than 20 psi (138 kPa) with a minimum flow of 2 gallons per minute (gpm) (0.1 L/s) at an outlet. The pressure shall not exceed 80 psi (552 kPa).

    E 502.6 Outlets. Water outlets shall be convenient to access and, where not piped to individual recreational vehicle sites, shall not exceed 300 feet (91 m) from a site. Provisions shall be made to prevent accumulation of standing water or the creation of muddy conditions at each water outlet. E 502.7 Storage Tanks. Water storage tanks shall be constructed of impervious materials, protected against contamination, and provided with locked, watertight covers. Overflow or ventilation openings shall be down-facing and provided with a corrosion-resistant screening of not less than number 24 mesh to prevent the entrance of insects and vermin. Water storage tanks shall not have direct connections to sewers.

    E 503.0 Recreational Vehicle Park Water Connec- tions for Individual Recreational Vehicles.

    E 503.1 Location. Where provided, the water connections for potable water to individual recreational vehicle sites shall be located on the left rear half of the site (left side of recreational vehicle) within 4 feet (1219 mm) of the stand. E 503.2 Water Riser Pipe. Each potable water connection shall consist of a water riser pipe that is equipped with a threaded male spigot located not less than 12 inches (305 mm) but not more than 24 inches (610 mm) above grade level for the attachment of a standard water hose. The water riser pipe shall be protected from physical damage in accordance with this code. This connection shall be equipped with a listed antisiphon backflow prevention device.

  • CPC § 502.6 High relevance — show source text

    E 502.6 Outlets. Water outlets shall be convenient to access and, where not piped to individual recreational vehicle sites, shall not exceed 300 feet (91 m) from a site. Provisions shall be made to prevent accumulation of standing water or the creation of muddy conditions at each water outlet. E 502.7 Storage Tanks. Water storage tanks shall be constructed of impervious materials, protected against contamination, and provided with locked, watertight covers. Overflow or ventilation openings shall be down-facing and provided with a corrosion-resistant screening of not less than number 24 mesh to prevent the entrance of insects and vermin. Water storage tanks shall not have direct connections to sewers.

    E 503.0 Recreational Vehicle Park Water Connec- tions for Individual Recreational Vehicles.

    E 503.1 Location. Where provided, the water connections for potable water to individual recreational vehicle sites shall be located on the left rear half of the site (left side of recreational vehicle) within 4 feet (1219 mm) of the stand. E 503.2 Water Riser Pipe. Each potable water connection shall consist of a water riser pipe that is equipped with a threaded male spigot located not less than 12 inches (305 mm) but not more than 24 inches (610 mm) above grade level for the attachment of a standard water hose. The water riser pipe shall be protected from physical damage in accordance with this code. This connection shall be equipped with a listed antisiphon backflow prevention device.

    E 504.0 Recreational Vehicle Park Drainage System. E 504.1 Where Required. An approved drainage system shall be provided in recreational vehicle parks for conveying and disposing of sewage. Where available, parks shall be connected to a public sewer system. E 504.2 Location. Sewer lines shall be located to prevent damage from vehicular traffic. E 504.3 Materials. Pipe and fittings installed in the drainage system shall be of material listed, approved, and installed in accordance with this code.

    E 504.4 Pipe Sizes. The minimum diameters of drainage laterals, branches, and mains serving recreational vehicle sites shall be in accordance with Table E 504.4.

    TABLE E 504.4

    PIPE SIZES

    MAXIMUM NUMBER OF
    RECREATIONAL VEHICLE
    STANDS SERVED    		 MINIMUM PIPE SIZES
    (inches)


    5    		 3

    36    		 4

    71    		 5

    120    		 6

    440    		 8

    For SI units: 1 inch = 25 mm

    E 504.5 Cleanouts. Cleanouts shall be provided in accordance with Chapter 7 of this code. E 504.6 Drainage Inlet. Where provided, the site drainage system inlet connections for individual recreational vehicles shall be located to prevent damage by the parking of recreational vehicles or automobiles and shall consist of a sewer riser extending vertically to grade. The minimum diameter of the sewer riser pipe shall be not less than 3 inches (80 mm) in diameter, and shall be provided with a 4 inch (100 mm) inlet or not less than a 3 inch (80 mm) female fitting. **E 504.6.1 Location.

  • CPC § 911.4.1.1 Medium relevance — show source text

    911.4.1.1 Size of Parallel Horizontal

    Branches. Parallel horizontal circuit vented branches shall be permitted to connect on the same floor level. Each separate circuit-vented horizontal branch that is interconnected shall be sized independently in accordance with Section 911.4.

    911.4.1.2 Size of Continuous Horizontal Branches. Two or more circuit vented systems continuous on the same horizontal branch shall be uniformly sized for the total discharge into the branch.

    911.5 Additional Fixtures. Fixtures, other than the circuitvented fixtures, are permitted to discharge to the horizontal branch drain. Such fixtures shall be located on the same floor as the circuit-vented fixtures and shall be either individually or common vented.

    912.0 Engineered Vent System. 912.1 General. The design and sizing of a vent system shall be permitted to be determined by accepted engineering practices. The system shall be designed by a registered design professional and approved in accordance with Section 301.5. 912.2 Minimum Requirements. An engineered vent system shall provide protection of the trap seal in accordance with Section 901.3.

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    CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE

    CHAPTER 10 - TRAPS AND INTERCEPTORS

    (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 BSC BSC-
    CG    		 SFM HCD Col6 Col7 DSA Col9 Col10 OSHPD Col12 Col13 Col14 Col15 Col16 Col17 BSCC DPH AGR DWR CEC CA SL SLC
    Adopting Agency BSC BSC-
    CG    		 SFM 1 2 1-AC AC ** SS** SS/CC 1 1R 2 3 4 5 6 6 6 6 6 6 6 6 6
    Adopt Entire Chapter X X X
    Adopt Entire Chapter as
    amended (amended
    sections listed below)    		 X X X X X X X X X
    Adopt only those sections
    that are listed below
    Chapter/Section
    1003.1 Exception 2 X X
    1010.2 X
    1010.3 X
    _1010.
  • CPC § 1503.8.2 Medium relevance — show source text

    (3) The total number of occupants shall be multiplied by the applicable estimated gray water discharge as provided above and the type of fixtures connected to the gray water system.

    1503.8.2 Commercial, Industrial, and Institu- tional Occupancies. The Authority Having Jurisdic- tion may utilize the gray water discharge procedures listed below, water use records or other documentation to estimate gray water discharge.

    1503.8.2.1 Lavatories. Daily discharge from lava- tories may be determined by the following equation:

    (Equation 15.1)

    Occupants X lavatory flow rate X 3

    Where:

    The number of occupants = square footage of the building divided by the occupant load factor from the California Plumbing Code Chapter 4, Table 4-1.

    Lavatory fixture flow rate, new construction = That from the California Green Building Standards (CAL- Green) Code Section 5.303.3.4

    Lavatory fixture flow rate, existing fixtures = Actual flow rate for existing fixtures

    3 = Average number of uses per person per day 1503.8.2.2 Showers. Daily gray water discharge from showers may be determined by the following equation:

    (Equation 15.2)

    Number of daily uses X shower flow rate X 5 minutes 1503.8.2.3 Commercial Clothes Washers. Daily gray water discharge from commercial clothes wash- ers may be determined by the following equation:

    (Equation 15.3)

    Cubic feet of capacity X Water Factor X 6

    Where:

    Water Factor = Gallons per cubic foot

    6 = Average number of uses per day

    Note: Cubic feet of capacity and Water Factor are contained in product specifications or are available from the washer manufacturer.

    1503.8.3 Daily Discharge. Gray water systems using tanks shall be designed to minimize the amount of time gray water is held in the tank and shall be sized to dis- tribute the total amount of estimated gray water on a daily basis.

    Exception: Approved on-site treated nonpotable gray

    water systems.

    1503.9 Gray Water System Components. Gray water system components shall comply with Section 1503.9.1 through Section 1503.9.4 .

    [HCD 1] Gray water system components shall comply with this chapter.

    1503.9.1 Surge Tanks. Where installed, surge tanks shall be in accordance with the following:

    (1) Surge tanks shall be constructed of solid, durable materials not subject to excessive corrosion or decay and shall be watertight. Aboveground surge tanks shall be protected from direct sunlight or shall be constructed of UV resistant materials including but not limited to heavily tinted or opaque plastic, fiber- glass, lined metal, concrete and wood. Surge tanks constructed of steel shall be approved by the Authority Having Jurisdiction, provided such tanks are in accordance with approved applicable standards.

    (2) Each surge tank shall be vented in accordance with this code. The vent size shall be determined based on

    the total gray water fixture units as outlined in this code.

    (3) Each surge tank shall have an access opening with lockable gasketed covers or approved equivalent to allow for inspection and cleaning.

  • CPC § 911.2.1 Medium relevance — show source text

    waste.

    911.2.1 Multiple Circuit Vents. When multiple circuit vents are interconnected according to Section 911.4.1, each individual circuit vent shall be sized according to Section 911.2. The vent pipe connecting each circuit vent shall be sized according to Table 703.2.

    911.3 Relief Vent. A 2 inch (50 mm) relief vent shall be provided for circuit-vented horizontal branches receiving the discharge of four or more water closets when connecting to a drainage stack that receives the discharge of soil or waste from upper horizontal branches.

    911.3.1 Connection and Installation. The relief vent

    shall connect to the horizontal branch between the stack and the most downstream trap arm of the circuit vent. The relief vent shall be installed on the vertical to the

    horizontal branch.

    911.3.2 Fixture Drain. The relief vent is permitted to serve as a fixture drain. Fixtures discharging to a relief vent shall be one or two fixture unit fixtures but shall not

    exceed a total of 4 fixture units.

    911.4 Slope and Size of Horizontal Branch. The vented section of the horizontal branch shall be uniformly sloped and not more than 1 inch per foot (83.3 mm/m). The entire length of the vented section of the horizontal branch shall be sized for the total drainage discharge to the branch according to Table 703.2.

    911.4.1 Multiple Circuit-Vented Branches. Circuitvented horizontal branches are permitted to be connected together. Each group of a maximum of eight fixtures shall be considered a separate circuit vent and shall be in accordance with Section 911.4.1.1 and Section 911.4.1.2.

    911.4.1.1 Size of Parallel Horizontal

    Branches. Parallel horizontal circuit vented branches shall be permitted to connect on the same floor level. Each separate circuit-vented horizontal branch that is interconnected shall be sized independently in accordance with Section 911.4.

    911.4.1.2 Size of Continuous Horizontal Branches. Two or more circuit vented systems continuous on the same horizontal branch shall be uniformly sized for the total discharge into the branch.

    911.5 Additional Fixtures. Fixtures, other than the circuitvented fixtures, are permitted to discharge to the horizontal branch drain. Such fixtures shall be located on the same floor as the circuit-vented fixtures and shall be either individually or common vented.

    912.0 Engineered Vent System. 912.1 General. The design and sizing of a vent system shall be permitted to be determined by accepted engineering practices. The system shall be designed by a registered design professional and approved in accordance with Section 301.5. 912.2 Minimum Requirements. An engineered vent system shall provide protection of the trap seal in accordance with Section 901.3.

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    CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE

    CHAPTER 10 - TRAPS AND INTERCEPTORS

    (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 § 1603.9.1 High relevance — show source text

    1603.9.1 Overflow Outlet Size. The overflow outlet

    shall be sized to accommodate the flow of the rainwater

    entering the tank and not less than the aggregate crosssectional area of inflow pipes.

    1603.10 Opening and Access Protection. Rainwater tank openings shall be protected to prevent the entrance of insects, birds, or rodents into the tank and piping systems .

    Rainwater tank access openings exceeding 12 inches (305 mm) in diameter shall be secured to prevent tampering and unintended entry by either a lockable device or other approved method.

    (A) Animals and Insects. Screens installed on vent pipes, inlets, and overflow pipes shall have an aperture of not greater than [1] ∕ 16 of an inch (1.6 mm) and shall be close fit- ting.

    (B) Human Access. A minimum of one access opening shall be provided to allow inspection and cleaning. Rainwater tank manholes and access openings shall be secured by either a lockable device or other approved method to pre- vent unauthorized access.

    1603.11 Marking. Rainwater tanks shall be permanently marked with the capacity and the language: “NONPOTABLE RAINWATER.” Where openings are provided to allow a person to enter the tank, the opening shall be marked with the following language: “DANGER-CONFINED SPACE.”

    1603.12 Storage Tank Venting. Where venting using drainage or overflow piping is not provided or is considered insufficient, a vent shall be installed on each tank. The vent shall extend from the top of the tank and terminate not less than 6 inches (152 mm) above grade and shall be provided with a vent sized in accordance with this code, and based on the size of the influent pipe . The vent terminal shall be directed downward and covered with a [1] ∕ 16 of an inch ( 1.6 mm) mesh screen to prevent the entry of vermin and insects. Tank vent pipes shall not be connected to the sanitary drainage system vent.

    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

    «

    «

    «

    «

    «

    «

    330 2025 CALIFORNIA PLUMBING CODE

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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.

  • CPC § 1603.17. Medium relevance — show source text

    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|

    For SI units: 1 micron = 1 µm, 1 gallon = 3.785 L

    ipated earth or other loads. Holding tank covers shall be capable of supporting an earth load of not less than 300 pounds per square foot (lb/ft [2] ) (1465 kg/m [2] ) where the tank is designed for underground installation. Below grade rainwater tanks installed underground shall be provided with manholes. Below grade storage tanks, located outside of the building, shall be provided with either a manhole not less than 24 inches (610 mm) square or a manhole with an inside diameter of not less than 24 inches (610 mm). Service ports in manhole cov- ers shall be not less than 8 inches (203 mm) in diameter. The manhole opening shall be not less than 20 inches (508 mm) in diameter and located not less than 4 inches (102 mm) above

    the surrounding grade. The surrounding grade shall be sloped away from the manhole. Underground tanks shall be ballasted, anchored, or otherwise secured, to prevent the tank from floating out of the ground where empty. The combined weight of the tank and hold down system shall meet or exceed the buoyancy force of the tank.

    1603.9 Drainage and Overflow. Rainwater storage tanks shall be provided with a means of draining and cleaning. The overflow drain shall not be equipped with a shutoff valve. The overflow outlet shall discharge in accordance with this code for storm drainage systems. Where discharging to the storm drainage system, the overflow drain and tank drain shall be protected from backflow of the storm drainage system by a backwater valve or other approved method. Back- water valves shall be installed so that access is provided to the working parts for service and repair.

    1603.9.1 Overflow Outlet Size. The overflow outlet

  • CPC § 415.9 Medium relevance — show source text

    [F] 415.9 Group H-2. Occupancies in Group H-2 shall be constructed in accordance with Sections 415.9.1 through 415.9.3 and the California Fire Code.

    [F] 415.9.1 Flammable and combustible liquids. The storage, handling, processing and transporting of flammable and combustible liquids in Group H-2 and H-3 occupancies shall be in accordance with Sections 415.9.1.1 through 415.9.1.9, the California Mechanical Code and the California Fire Code .

    [F] 415.9.1.1 Mixed occupancies. Where the storage tank area is located in a building of two or more occupancies and the quantity of liquid exceeds the maximum allowable quantity for one control area, the use shall be completely separated from adjacent occupancies in accordance with the requirements of Section 508.4.

    [F] 415.9.1.1.1 Height exception. Where storage tanks are located within a building not more than one story above grade plane, the height limitation of Section 504 shall not apply for Group H.

    [F] 415.9.1.2 Tank protection. Storage tanks shall be noncombustible and protected from physical damage. Fire barriers or horizontal assemblies or both around the storage tanks shall be permitted as the method of protection from physical damage.

    [F] 415.9.1.3 Tanks. Storage tanks shall be approved tanks conforming to the requirements of the California Fire Code .

    [F] 415.9.1.4 Leakage containment. A liquid-tight containment area compatible with the stored liquid shall be provided. The method of spill control, drainage control and secondary containment shall be in accordance with the California Fire Code .

    Exception: Rooms where only double-wall storage tanks conforming to Section 415.9.1.3 are used to store Class I, II and IIIA flammable and combustible liquids shall not be required to have a leakage containment area.

    [F] 415.9.1.5 Leakage alarm. An approved automatic alarm shall be provided to indicate a leak in a storage tank and room. The alarm shall sound an audible signal, 15 dBa above the ambient sound level, at every point of entry into the room in which the leaking storage tank is located. An approved sign shall be posted on every entry door to the tank storage room indicating the potential hazard of the interior room environment, or the sign shall state, “WARNING, WHEN ALARM SOUNDS, THE ENVIRONMENT WITHIN THE ROOM MAY BE HAZARDOUS.” The leakage alarm shall be supervised in accordance with Chapter 9 to transmit a trouble signal.

    [F] 415.9.1.6 Tank vent. Storage tank vents for Class I, II or IIIA liquids shall terminate to the outdoor air in accordance with the California Fire Code .

    [F] 415.9.1.7 Room ventilation. Storage tank areas storing Class I, II or IIIA liquids shall be provided with mechanical ventilation. The mechanical ventilation system shall be in accordance with the California Mechanical Code and the California Fire Code .

    [F] 415.9.1.8 Explosion venting. Where Class I liquids are being stored, explosion venting shall be provided in accordance with the California Fire Code .

  • CPC § 1603.5 Medium relevance — show source text

    1603.5 Rainwater Storage Tanks . . . . . . .329

    1603.6 Location . . . . . . . . . . . . . . . . . . . .329

    1603.7 Above Grade . . . . . . . . . . . . . . . .329

    1603.8 Below Grade . . . . . . . . . . . . . . . . .329

    Table 1603.4 Minimum Water Quality . . . . . . . .330

    1603.9 Drainage and Overflow . . . . . . . . .330

    1603.10 Opening and Access Protection . . .330

    1603.11 Marking . . . . . . . . . . . . . . . . . . . . .330

    1603.12 Storage Tank Venting . . . . . . . . . .330

    1603.13 Pumps . . . . . . . . . . . . . . . . . . . . .330

    1603.14 Roof Drains . . . . . . . . . . . . . . . . . .331

    1603.15 Water Quality Devices and Equipment . . . . . . . . . . . . . . . . . .331

    1603.16 Freeze Protection . . . . . . . . . . . . .331

    1603.17 Debris Removal . . . . . . . . . . . . . .331

    1603.18 Required Filters . . . . . . . . . . . . . .331

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    1603.19 Roof Gutters . . . . . . . . . . . . . . . . .331

    1603.20 Rainwater Diversion Valves . . . . .331

    1604.0 Signs . . . . . . . . . . . . . . . . . . . . . . .331

    1604.1 General . . . . . . . . . . . . . . . . . . . . .331

    1604.2 Commercial, Industrial,

    Institutional and Residential

    Restroom Signs . . . . . . . . . . . . . .331

    1604.3 Equipment Room Signs . . . . . . . .331

    1605.0 Inspection and Testing . . . . . . . . .331

    1605.1 General . . . . . . . . . . . . . . . . . . . . .331

    1605.2 Supply System Inspection and Test . . . . . . . . . . . . . . . . . . . .331

    1605.3 Cross-Connection Inspection and Testing . . . . . . . . . . . . . . . . . .331

    CHAPTER 17 REFERENCED STANDARDS . . .333

    1701.0 General . . . . . . . . . . . . . . . . . . . . .335

    1701.1 Standards . . . . . . . . . . . . . . . . . . .335

    Table 1701.1 Referenced Standards . . . . . . . . .335

    1701.2 Standards, Publications, Practices, and Guides . . . . . . . . .352

    Table 1701.2 Standards, Publications, Practices, and Guides . . . . . . . . .352

  • CPC § 415.9.1.3 Medium relevance — show source text

    Exception: Rooms where only double-wall storage tanks conforming to Section 415.9.1.3 are used to store Class I, II and IIIA flammable and combustible liquids shall not be required to have a leakage containment area.

    [F] 415.9.1.5 Leakage alarm. An approved automatic alarm shall be provided to indicate a leak in a storage tank and room. The alarm shall sound an audible signal, 15 dBa above the ambient sound level, at every point of entry into the room in which the leaking storage tank is located. An approved sign shall be posted on every entry door to the tank storage room indicating the potential hazard of the interior room environment, or the sign shall state, “WARNING, WHEN ALARM SOUNDS, THE ENVIRONMENT WITHIN THE ROOM MAY BE HAZARDOUS.” The leakage alarm shall be supervised in accordance with Chapter 9 to transmit a trouble signal.

    [F] 415.9.1.6 Tank vent. Storage tank vents for Class I, II or IIIA liquids shall terminate to the outdoor air in accordance with the California Fire Code .

    [F] 415.9.1.7 Room ventilation. Storage tank areas storing Class I, II or IIIA liquids shall be provided with mechanical ventilation. The mechanical ventilation system shall be in accordance with the California Mechanical Code and the California Fire Code .

    [F] 415.9.1.8 Explosion venting. Where Class I liquids are being stored, explosion venting shall be provided in accordance with the California Fire Code .

    [F] 415.9.1.9 Tank openings other than vents. Tank openings other than vents from tanks inside buildings shall be designed to ensure that liquids or vapor concentrations are not released inside the building.

    [F] 415.9.2 Liquefied petroleum gas facilities. The construction and installation of liquefied petroleum gas facilities shall be in accordance with the requirements of this code, the California Fire Code, the California Plumbing Code, the California Mechanical Code and NFPA 58.

    [F] 415.9.3 Dry cleaning plants. The construction and installation of dry cleaning plants shall be in accordance with the requirements of this code, the California Mechanical Code, the California Plumbing Code and NFPA 32. Dry cleaning solvents and systems shall be classified in accordance with the California Fire Code .

    [F] 415.10 Groups H-3 and H-4. Groups H-3 and H-4 shall be constructed in accordance with the applicable provisions of this code and the California Fire Code .

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    SPECIAL DETAILED REQUIREMENTS BASED ON OCCUPANCY AND USE

    [F] 415.10.1 Flammable and combustible liquids. The storage, handling, processing and transporting of flammable and combustible liquids in Group H-3 occupancies shall be in accordance with Section 415.9.1.

    [F] 415.10.2 Gas rooms. Where gas rooms are provided, such rooms shall be separated from other areas by not less than 1-hour fire barriers constructed in accordance with Section 707 or horizontal assemblies constructed in accordance with Section 711, or both.

  • CPC § 2306.3 Medium relevance — show source text

    2306.3 Security. Above-ground tanks for the storage of liquid motor fuels shall be safeguarded from public access or unauthorized entry in an approved manner.

    2306.4 Physical protection. Guard posts complying with Section 312 or other approved means shall be provided to protect aboveground tanks against impact by a motor vehicle unless the tank is listed as a protected above-ground tank with vehicle impact protection.

    2306.5 Secondary containment. Above-ground tanks shall be provided with drainage control or diking in accordance with Chapter 57. Drainage control and diking is not required for listed secondary containment tanks. Secondary containment systems shall be monitored either visually or automatically. Enclosed secondary containment systems shall be provided with emergency venting in accordance with Section 2306.6.2.5.

    2306.6 Piping, valves, fittings and ancillary equipment for use with flammable or combustible liquids. The design, fabrication, assembly, testing and inspection of piping, valves, fittings and ancillary equipment for use with flammable or combustible liquids shall be in accordance with Chapter 57 and Sections 2306.6.1 through 2306.6.3.

    2306.6.1 Protection from damage. Piping shall be located such that it is protected from physical damage.

    2306.6.2 Piping, valves, fittings and ancillary equipment for above-ground tanks for Class I, II and III liquids. Piping, valves, fittings and ancillary equipment for above-ground tanks storing Class I, II and III liquids shall comply with Sections 2306.6.2.1 through 2306.6.2.6.

    2306.6.2.1 Tank openings. Tank openings for above-ground tanks shall be through the top only.

    2306.6.2.2 Fill-pipe connections. The fill pipe for above-ground tanks shall be provided with a means for making a direct connection to the tank vehicle’s fuel-delivery hose so that the delivery of fuel is not exposed to the open air during the filling operation. Where any portion of the fill pipe exterior to the tank extends below the level of the top of the tank, a check valve shall be installed in the fill pipe not more than 12 inches (305 mm) from the fill-hose connection.

    2306.6.2.3 Overfill protection. Overfill protection shall be provided for above-ground flammable and combustible liquid storage tanks in accordance with Sections 5704.2.7.5.8 and 5704.2.9.7.5.

    2306.6.2.4 Siphon prevention. An approved antisiphon method shall be provided in the piping system to prevent flow of liquid by siphon action.

    2306.6.2.5 Emergency relief venting. Above-ground storage tanks, tank compartments and enclosed secondary containment spaces shall be provided with emergency relief venting in accordance with Chapter 57.

    2306.6.2.6 Spill containers. A spill container having a capacity of not less than 5 gallons (19 L) shall be provided for each fill connection. For tanks with a top fill connection, spill containers shall be noncombustible and shall be fixed to the tank and

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    MOTOR FUEL-DISPENSING FACILITIES AND REPAIR GARAGES

    equipped with a manual drain valve that drains into the primary tank. For tanks with a remote fill connection, a portable spill container is allowed.

  • CPC § 5704.2.5 Medium relevance — show source text

    Exception: Areas designated as smoking and hot work areas, and areas where hot work permits have been issued in accordance with this code.

    5704.2.5 Explosion control. Explosion control shall be provided in accordance with Section 911 for indoor tanks.

    5704.2.6 Separation from incompatible materials. Storage of flammable and combustible liquids shall be separated from incompatible materials in accordance with Section 5003.9.8.

    Grass, weeds, combustible materials and waste Class I, II or IIIA liquids shall not be accumulated in an unsafe manner at a storage site.

    5704.2.7 Design, fabrication and construction requirements for tanks. The design, fabrication and construction of tanks shall comply with NFPA 30. Each tank shall bear a permanent nameplate or marking indicating the standard used as the basis of design.

    5704.2.7.1 Materials used in tank construction. The materials used in tank construction shall be in accordance with NFPA 30. The materials of construction for tanks and their appurtenances shall be compatible with the liquids to be stored.

    5704.2.7.2 Pressure limitations for tanks. Tanks shall be designed for the pressures to which they will be subjected in accordance with NFPA 30.

    5704.2.7.3 Tank vents for normal venting. Tank vents for normal venting shall be installed and maintained in accordance with Sections 5704.2.7.3.1 through 5704.2.7.3.5.3.

    5704.2.7.3.1 Vent lines. Vent lines from tanks shall not be used for purposes other than venting unless approved.

    5704.2.7.3.2 Vent-line flame arresters and pressure-vacuum vents. Listed or approved flame arresters or pressurevacuum (PV) vents that remain closed unless venting under pressure or vacuum conditions shall be installed in normal vents of tanks containing Class IB and IC liquids.

    Vent-line flame arresters shall be installed in accordance with their listing or API 2000 and maintained in accordance with Section 21.8.6 of NFPA 30 or API 2000. In-line flame arresters in piping systems shall be installed and maintained in accordance with their listing or API 2028. Pressure-vacuum vents shall be installed in accordance with Section 21.4.3 of NFPA 30 or API 2000 and maintained in accordance with Section 21.8.6 of NFPA 30 or API 2000.

    Exception: Where determined by the fire code official that the use of these devices can result in damage to the tank.

    5704.2.7.3.3 Vent pipe outlets. Vent pipe outlets for tanks storing Class I, II or IIIA liquids shall be located such that the vapors are released at a safe point outside of buildings and not less than 12 feet (3658 mm) above the finished ground level. Vapors shall be discharged upward or horizontally away from adjacent walls to assist in vapor dispersion. Vent outlets shall be located such that flammable vapors will not be trapped by eaves or other obstructions and shall be not less than 5 feet (1524 mm) from building openings or lot lines of properties that can be built on. Vent outlets on atmospheric tanks storing Class IIIB liquids are allowed to discharge inside a building where the vent is a normally closed vent.

    Exception: Vent pipe outlets on tanks storing Class IIIB liquid inside buildings and connected to fuel-burning equipment shall be located such that the vapors are released to a safe location outside of buildings.

  • CPC § 1601.11 Medium relevance — show source text

    1601.11 Abandonment . . . . . . . . . . . . . . . .328

    1601.12 Sizing . . . . . . . . . . . . . . . . . . . . . .328

    1602.0 Nonpotable Rainwater Catchment Systems . . . . . . . . . . .328

    1602.1 General . . . . . . . . . . . . . . . . . . . . .328

    1602.2 Plumbing Plan Submission . . . . . .328

    1602.3 System Changes . . . . . . . . . . . . .328

    1602.4 Connections to Potable or Reclaimed (Recycled) Water Systems . . . . . . . . . . . . . . .328

    1602.5 Initial Cross-Connection Test . . . .328

    1602.6 Sizing . . . . . . . . . . . . . . . . . . . . . .328

    1602.7 Rainwater Catchment System Materials . . . . . . . . . . . . . . . . . . . .329

    1602.8 Rainwater Catchment System Color and Marking Information . . .329

    1602.9 Deactivation and Drainage for Cross-Connection Test . . . . . . . . .329

    1603.0 Design and Installation . . . . . . . . .329

    1603.1 Rainwater Catchment Systems . . .329

    1603.2 Outside Hose Bibbs . . . . . . . . . . .329

    1603.3 Rainwater Catchment

    Collection Surfaces . . . . . . . . . . . .329

    1603.4 Minimum Water Quality . . . . . . . .329

    1603.5 Rainwater Storage Tanks . . . . . . .329

    1603.6 Location . . . . . . . . . . . . . . . . . . . .329

    1603.7 Above Grade . . . . . . . . . . . . . . . .329

    1603.8 Below Grade . . . . . . . . . . . . . . . . .329

    Table 1603.4 Minimum Water Quality . . . . . . . .330

    1603.9 Drainage and Overflow . . . . . . . . .330

    1603.10 Opening and Access Protection . . .330

    1603.11 Marking . . . . . . . . . . . . . . . . . . . . .330

    1603.12 Storage Tank Venting . . . . . . . . . .330

    1603.13 Pumps . . . . . . . . . . . . . . . . . . . . .330

    1603.14 Roof Drains . . . . . . . . . . . . . . . . . .331

    1603.15 Water Quality Devices and Equipment . . . . . . . . . . . . . . . . . .331

    1603.16 Freeze Protection . . . . . . . . . . . . .331

    1603.17 Debris Removal . . . . . . . . . . . . . .331

    1603.18 Required Filters . . . . . . . . . . . . . .331

    2025 CALIFORNIA PLUMBING CODE xlv

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

  • CPC § 1603.0 Medium 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.

Frequently asked questions

What is the minimum vent termination height above grade?

The CPC requires the vent to terminate not less than 6 inches (152 mm) above grade; see § 1603.12 .

Can a tank vent be tied into the building sanitary vent?

No. Tank vent pipes shall not be connected to the sanitary drainage system — this is explicitly stated in § 1603.12 .

Is there a required mesh size for vent and inlet screens?

Yes — the chapter text requires screens to exclude insects/rodents. The main text calls for 1/16 in (1.6 mm) mesh in § 1603.12/§ 1603.10, while Appendix K sometimes offers alternate mesh guidance; reconcile with the AHJ — see § 1603.12 and § 1603.10 .

Do underground tanks need anchors?

Yes — underground tanks must be ballasted, anchored or otherwise secured to prevent flotation when empty; the combined weight of tank and hold‑down system must equal or exceed buoyancy forces — § 1603.8 and Appendix K (K 105.3.2) .

How must overflow outlets be sized?

The overflow outlet must be sized to accommodate the flow entering the tank and be not less than the aggregate cross‑sectional area of the inflow pipes — § 1603.9.1 .

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