CALGreen · California Green Building Standards Code (CALGreen)
Indoor potable water reduction targets and graywater irrigation systems
If your project uses Appendix A5 voluntary measures, CALGreen requires a **12%** indoor potable‑water reduction for Tier 1 projects (**§ A5.303.2.3.1**) and, if using the graywater elective, installation of a graywater collection system for **onsite subsurface irrigation** from baths, showers, lavatories and laundry (**§ A5.304.8**). All nonpotable systems must meet the California Plumbing Code (**§ A5.305.1**).
Last reviewed: July 6, 2026
What the code requires — plain English
- Projects following CALGreen voluntary Appendix A5 must meet the indoor potable water reduction percentage in § A5.303.2.3.1 (the Tier 1 12‑percent target) when that measure is selected. § A5.303.2.3.1 is the controlling provision for the Tier 1 indoor potable water reduction target.
- Appendix A5 also requires installation of a graywater collection system for onsite subsurface irrigation using graywater from bathtubs, showers, bathroom washbasins and laundry when the graywater elective is used: see § A5.304.8.
- Where a nonpotable water system is used (indoor or outdoor), the system must comply with the current California Plumbing Code — see § A5.305.1.
The single most important rule: if you select the Appendix A5 voluntary measures, meet the percent reduction required by the specific A5 indoor‑water section and install any graywater systems only to the technical requirements of the California Plumbing Code. § A5.303.2.3.1, § A5.304.8, § A5.305.1.
Requirements in detail
1) Indoor potable water‑use reduction (what the percentage means)
- The code text identifies a 12‑percent indoor potable water reduction target for the Tier 1 voluntary path in Appendix A5. This target is the requirement in § A5.303.2.3.1.
- Appendix A5 sets baseline flows and a performance method (see Table A5.303.2.2) for calculating baseline indoor water use when doing the performance calculation. Use the baseline table when computing the percent reduction.
2) Graywater irrigation system (scope and source water)
- § A5.304.8 requires installation of a graywater collection system sized/installed for onsite subsurface irrigation using graywater from bathtubs, showers, bathroom wash basins and laundry. The section also directs the designer to the California Plumbing Code for design and installation details.
- Important emphasized points from that language: the system is intended for subsurface irrigation (not permitted as an above‑ground spray irrigation method under this provision) and the listed fixture sources are the eligible graywater contributors.
3) Nonpotable water systems compliance backstop
- § A5.305.1 states that nonpotable water systems for indoor and outdoor use must comply with the current California Plumbing Code. That means sizing, siting, separation from potable supplies, cross‑connection protection, health/safety measures, and irrigation field/mulch‑basin details come from the Plumbing Code.
Quick reference table — decision dimensions and code pointers
| Decision dimension | Key value / requirement | Code reference |
|---|---|---|
| Tier 1 indoor potable water reduction target | 12% reduction (Tier 1) | § A5.303.2.3.1 |
| Baseline for performance method | Use Table A5.303.2.2 baseline flows to compute baseline | Table A5.303.2.2 |
| Graywater irrigation required elements | Install graywater collection for onsite subsurface irrigation using water from bathtubs, showers, bathroom wash basins and laundry | § A5.304.8 |
| Technical compliance (design, health, safety) | Nonpotable systems must comply with the California Plumbing Code | § A5.305.1 |
| Voluntary nature of Appendix A5 | Appendix A5 measures are voluntary unless locally adopted (see Appendix scope) — confirm local adoption | Appendix A5 scope (see tier/voluntary notes) |
Exceptions & special cases
- Appendix A5 is a set of voluntary measures unless your local jurisdiction adopts them; verify local adoption before assuming A5 measures are mandatory.
- The graywater provision in § A5.304.8 points to the California Plumbing Code for details — the CALGreen section does not itself provide all design, separation, groundwater, or irrigation field sizing rules. Designers must follow the CPC for those technical elements.
- If a project instead uses recycled water or is regulated under another local water‑efficiency landscape ordinance (e.g., MWELO), those recycled‑water irrigation rules and connections may supersede or alter the approach — see related sections (listed below).
Common mistakes
- Treating Appendix A5 items as automatically mandatory without checking local adoption. Confirm local code adoption first.
- Designing or installing graywater as above‑ground spray irrigation when § A5.304.8 specifies subsurface irrigation (and the CPC controls permitted methods).
- Omitting California Plumbing Code compliance for nonpotable systems. § A5.305.1 requires CPC compliance — don’t rely on CALGreen alone for technical design.
- Using baseline or percent targets without applying the baseline flows in Table A5.303.2.2 when doing a performance calculation — use the table for consistent baseline determinations.
Worked example — concrete scenario with numbers
Scenario: A building owner opts into Appendix A5 Tier 1 voluntary measures and calculates building baseline indoor potable water demand using the performance method. Suppose the calculated baseline annual indoor potable water use is 100,000 gallons per year (this baseline number is a hypothetical example for illustration; actual baseline must be computed from Table A5.303.2.2 and the project’s fixture counts/occupants). Using the Tier 1 reduction requirement:
- Required Tier 1 reduction = 12% per § A5.303.2.3.1.
- Required potable water savings = 100,000 gal/yr × 12% = 12,000 gal/yr.
- Target post‑compliance potable use = 100,000 − 12,000 = 88,000 gal/yr.
How graywater fits: install a graywater collection system for subsurface irrigation (per § A5.304.8) to help reduce potable irrigation use; detailed capture, storage, and application volumes must be sized per the California Plumbing Code and site‑specific irrigation needs. The CALGreen section names the system requirement but defers the technical sizing and health/safety rules to the CPC.
(If you need a worked numeric example that sizes a graywater system from showers and laundry to meet the 12% savings, I can run a capture/irrigation mass‑balance calculation — but the CPC and project fixture schedules are required inputs for accurate sizing.)
Related provisions (select)
- § A5.303.5 — Dual plumbing requirements (potable and recycled water piping where recycled water is available).
- § A5.304.2 — Requirement for separate meters/submeters for indoor and outdoor potable water use for certain landscape sizes.
- Table A5.303.2.2 — Water use baseline (baseline fixture flows used in performance calculations).
- § A4.305.1 — Graywater provisions in the residential voluntary appendix (useful if project includes residential portions).
- § A5.601.1 — Appendix A5 scope noting voluntary nature unless locally adopted.
Code references
Grounded in the retrieved California Green Building Standards Code (CALGreen) — click a citation to read the verbatim passage:
CALGreen § 303.4 High relevance — show source text
APPENDIX A5 — NONRESIDENTIAL VOLUNTARY MEASURES
A5.303.4 Water conserving plumbing fixtures and fittings.
A5.303.4.1 Nonwater urinals. Nonwater urinals with drain cleansing action are installed in accordance with the California Plumbing Code .
Where approved, nonwater urinals with drain cleansing action (formerly urinal, hybrids) as defined in Chapter 2, shall be considered waterless urinals.
A5.303.5 Dual plumbing. New buildings and facilities shall be dual plumbed for potable and recycled water systems for toilet flushing when recycled water is available as determined by the enforcement authority.
SECTION A5.304—OUTDOOR WATER USE
A5.304.1 Reserved.
A5.304.2 Outdoor water use. For new water service not subject to the provisions of Water Code Section 535, separate meters or submeters shall be installed for indoor and outdoor potable water use for landscaped areas of at least 500 square feet but not more than 1,000 square feet.
A5.304.6 Restoration of areas disturbed by construction. Restore all landscape areas disturbed during construction by planting with local adaptive and/or noninvasive vegetation.
A5.304.7 Previously developed sites. On previously developed or graded sites, restore or protect at least 50 percent of the site area with adaptive and/or noninvasive vegetation. Projects complying with Section A5.106.3, Item 3 may apply vegetated roof surface to this calculation if the roof plants meet the definition of adaptive and noninvasive.
Exception: Area of the building footprint is excluded from the calculation.
A5.304.8 Graywater irrigation system. Install a graywater collection system for onsite subsurface irrigation using graywater collected from bathtubs, showers, bathroom wash basins and laundry water. See California Plumbing Code.
SECTION A5.305—WATER REUSE
A5.305.1 Nonpotable water systems. Nonpotable water systems for indoor and outdoor use shall comply with the current edition of the California Plumbing Code.
A5.305.2 Irrigation systems. Irrigation systems regulated by a local water efficient landscape ordinance or by the California Department of Water Resources Model Water Efficient Landscape Ordinance (MWELO) shall use recycled water.
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APPENDIX A5-22 2025 CALIFORNIA GREEN BUILDING STANDARDS CODE
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CALIFORNIA GREEN BUILDING STANDARDS CODE – MATRIX ADOPTION TABLE
APPENDIX A5 – NONRESIDENTIAL VOLUNTARY MEASURES
DIVISION A5.4 – MATERIAL CONSERVATION AND RESOURCE EFFICIENCY
(Matrix Adoption Tables are nonregulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)
CALGreen § 301.1 High relevance — show source text
Voluntary Measures 301.1, 306 Voluntary Tiers 304, 305, 306, A4.601, A5.601
Water Resistance and Moisture Management 5.407, 5.505, A4.407, Appendix A6.1 (OSHPD) A5.407 Moisture control 4.505, 5.407.2, 5.505, Appendix A6.1 (OSHPD) A5.407.9, Appendix A6.1 (OSHPD) A5.505.2 Weather protection 5.407.1, A5.407.3
Water Reuse Systems A4.305 Graywater A4.305.1, A5.304.8 Recycled water for landscape irrigation A4.305.3 Recycled water piping A4.305.2 Water Use, Indoor 4.303, 5.303, A4.303, A5.203
Appliances A4.303.3, A5.303.3, Appendix A6.1 (OSHPD) A5.210 Dual plumbing A5.303.5 Fixture flow rates 4.303.1, Table A5.303.2.3.1, 5.303.2.3.1, A4.303 Kitchen faucets and dishwashers
A4.303.1
Meters 4.303.2, 5.303.1 Multiple showerheads serving one shower 4.303.1.3.2, 5.303.3.3.2 Nonwater urinals and waterless toilets
A4.303.4, A5.303.4.1 Plumbing fixtures and fittings 4.303.1, 4.303.2, 5.303.3, 5.303.6 Tier 1, 12% savings; Tier 2, 20% savings; and 25% savings A5.303.2.1, A5.303.2.3.1, A5.303.2.3.2,
A5.303.2.3.3
Wastewater reduction 5.303.4
Water Use Baseline Table A5.303.2.2
Water Use, Outdoor 4.304, 5.304, A4.304, A5.304
Graywater irrigation system A5.304.8 Low-water consumption irrigation system A4.304.1 Outdoor potable water meters A4.304.3, A5.304.2 Potable water elimination A4.304.2 Previously developed sites A5.304.7 Rainwater or stormwater collection systems A4.304.1 Restoration of areas disturbed by construction A5.304.6 Worksheet Baseline Water Use Chapter 8, (WS-1) 12%, 20% or 25% Reduction Water Use Calculation Table Chapter 8, (WS-2) Building Reuse Chapter 8, (WS-3) Whole Building Life Cycle Assessment 5.409.2, Chapter 8, (WS-4) Product GWP Compliance— Prescriptive Path 5.409.3, Chapter 8, (WS-5) Building Reuse Tier 1 and Tier 2 Chapter 8, (WS-6) Whole Building Life Cycle Assessment A5.409.2, Chapter 8, (WS-7) Product GWP Compliance— Prescriptive Path A5.409.3,
CALGreen § 601.3.4 Medium relevance — show source text
A5.601.3.4 Voluntary measures for Tier 2. In addition to the provisions of Sections A5.601.3.1 and A5.601.3.3 above, compliance with the following voluntary measures from Appendix A5 is required for Tier 2:
- From Division A5.1, a. Comply with the designated parking requirements for fuel efficient vehicles for a minimum of 50 percent of parking capacity per Section A5.106.5.1. b. Electric vehicle (EV) charging [N] and Table A5.106.5.3.2 with footnotes. c. Comply with thermal emittance, solar reflectance or SRI values for cool roofs in Section A5.106.11.2 and Table A5.106.11.2.3. [1]
d. Comply with three elective measures selected from this division.
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APPENDIX A5 — NONRESIDENTIAL VOLUNTARY MEASURES
From Division A5.2 comply with TWO of the following:
Outdoor lighting as described in A5.203.1.1.1.
Service water heating in restaurants as described in A5.203.1.1.2.
Warehouse Dock Seal Doors A5.203.1.1.3.
Daylight Design Power Adjustments 5.203.1.1.4.
Exhaust Air Heat Recovery A5.203.1.1.5.
From Division A5.3,
a. Comply with the 20-percent reduction for indoor potable water use in Section A5.303.2.3.2. b. Comply with three elective measures selected from this division.
- From Division A5.4,
a. Comply with recycled content of 15 percent of materials based on estimated total cost, or use two products from Table A5.405.4 for at least 75 percent by cost in Section A5.405.4.1. b. Comply with the 80-percent reduction in construction and demolition waste in Section A5.408.3.1. c. Comply with three elective measures selected from this division.
- From Division A5.5,
a. Comply with resilient flooring systems for 100 percent of resilient flooring in Section A5.504.4.7.1. Exception: Allowance may be permitted in Tier 2 for up to 5-percent specialty purpose flooring. b. Comply with thermal insulation meeting 2009 CHPS low-emitting materials list and no added formaldehyde in Section A5.504.4.8.1.
c. Comply with three elective measures selected from this division. 6. Comply with three additional elective measures selected from any division.
1 Cool roof is required for compliance with Tiers 1 and 2 and may be used to meet energy standards in Part 6, exceed energy standards and to mitigate heat island effect.
A5.601.4 Compliance verification. Compliance with Section A5.601.2 or A5.601.3 shall be as required in Chapter 7 of this code. Compliance documentation shall be made part of the project record as required in Section 5.410.2 or 5.410.3.
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CALGreen § 601.2.4 Medium relevance — show source text
A5.601.2.4 Voluntary measures for Tier 1. In addition to the provisions of Sections A5.601.2.1 and A5.601.2.3 above, compliance with the following voluntary measures from Appendix A5 is required for Tier 1:
- From Division A5.1, a. Comply with the designated parking requirements for high-efficiency vehicles for a minimum of 35 percent of parking capacity per Section A5.106.5.1. b. Electric vehicle (EV) charging [N] and Table A5.106.5.3.1 w/ footnotes. c. Comply with thermal emittance, solar reflectance or SRI values for cool roofs in Section A5.106.11.2 and Table A5.106.11.2.2. [1]
d. Comply with one elective measure selected from this division. 2. From Division A5.2 comply with ONE of the following:
Outdoor lighting as described in A5.203.1.1.1.
Service water heating in restaurants as described in A5.203.1.1.2.
Warehouse Dock Seal Doors A5.203.1.1.3.
Daylight Design Power Adjustments 5.203.1.1.4.
Exhaust Air Heat Recovery A5.203.1.1.5.
From Division A5.3,
a. Comply with the 12-percent reduction for indoor potable water use in Section A5.303.2.3.1. b. Comply with one elective measure selected from this division.
- From Division A5.4,
a. Comply with recycled content of 10 percent of materials based on estimated total cost, or use two products from Table A5.405.4 for at least 75 percent by cost in Section A5.405.4. b. Comply with the 65-percent reduction in construction and demolition waste in Section A5.408.3.1. c. Comply with one elective measure selected from this division.
- From Division A5.5,
a. Comply with resilient flooring systems for 90 percent of resilient flooring in Section A5.504.4.7. b. Comply with thermal insulation meeting 2009 CHPS low-emitting materials list in Section A5.504.4.8. c. Comply with one elective measure selected from this division. 6. Comply with one additional elective measure selected from any division.
1 Cool roof is required for compliance with Tiers 1 and 2 and may be used to meet energy standards in Part 6, exceed energy standards and to mitigate heat island effect.
A5.601.3 CALGreen Tier 2.
A5.601.3.1 Prerequisites. To achieve CALGreen tier status, a project must meet all of the mandatory measures in Chapter 5 and, in addition, meet the provisions of this section.
A5.601.3.2 Energy performance. For the purposes of mandatory energy efficiency standards in this code, the California Energy Commission will continue to adopt mandatory standards.
A5.601.3.3 Tier 2. Comply with the energy efficiency requirements in Section A5.203.1.1 and Section A5.203.1.2.2.
CALGreen § 5.2 Medium relevance — show source text
1**
Planning and Design||1 additional Elective from Division A5.1|3 additional Electives from Division A5.1| |DIVISION 5.2
Energy Efficiency|Energy Performance2a, 2b|Outdoor lighting power 90%
of Part 6 allowance|Outdoor lighting power 90%
of Part 6 allowance| |||If applicable, solar water-heating system
with minimum solar savings fraction of 0.15|If applicable, solar water-heating system
with minimum solar savings fraction of 0.15| |||Warehouse door seals|Warehouse door seals| |||Comply with day lighting requirements|Comply with day lighting requirements| |||Exhaust heat recovery|Exhaust heat recovery| |||Energy Budget 95% or 90%
of Part 6 calculated value of allowance|Energy Budget 90% or 85%
of Part 6 calculated value of allowance| |DIVISION 5.3
Water Efficiency
and Conservation|Indoor Water Use|12% Savings|20% Savings| |DIVISION 5.3
Water Efficiency
and Conservation||1 additional Elective from Division A5.3|3 additional Electives from Division A5.3| |DIVISION 5.4
Material Conservation
and Resource Efficiency3|Construction Waste Reduction|At least 65% reduction|At least 80% reduction| |DIVISION 5.4
Material Conservation
and Resource Efficiency3|Recycled Content|Utilize recycled content materials for
10% of total material cost|Utilize recycled content materials for
15% of total material cost| |DIVISION 5.4
Material Conservation
and Resource Efficiency3|Cradle-to-Grave
Whole Building Life Cycle
Assessment|See Section A5.409.1, Section A5.409.2
and Section A5.409.2.3 requirements|See Section A5.409.1, Section A5.409.2
and Section A5.409.2.3 requirements| |DIVISION 5.4
Material Conservation
and Resource Efficiency3|Product GWP compliance –
prescriptive path|See Section A5.409.1, Section A5.409.2
and Section A5.409.2.3 requirements|See Section A5.409.1, Section A5.409.2
and Section A5.409.2.3 requirements| |DIVISION 5.4
Material Conservation
and Resource Efficiency3||1 additional Elective
from Division A5.4|3 additional Electives
from Division A5.4| |DIVISION 5.5
Environmental Quality|Low-VOC Resilient Flooring|90% of flooring meets VOC limits|100% of flooring meets VOC limits1| |DIVISION 5.5
Environmental Quality|Low-VOC Thermal Insulation|Comply with VOC limits|Install no-added formaldehyde
insulation and comply with VOC limits| |DIVISION 5.5
Environmental Quality||1 additional Elective from Division A5.5|3 additional Electives from Division A5.CALGreen § 409.4 Medium relevance — show source text
Solar access is the ratio of solar insolation including shade to the
solar insolation without shade. Shading from obstructions located on the roof or any other part of the building shall not be included in the determination of annual solar access.
3.
Life cycle assessment compliant with Section A5.409.4 in this code may be substituted for prescriptive measures from Division A5.4.|A5.601.1 Scope. The measures contained in this appendix are not mandatory unless adopted by local government as specified in Section 101.7. The provisions of this section outline means of achieving enhanced construction or reach levels by incorporating addi
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APPENDIX A5 — NONRESIDENTIAL VOLUNTARY MEASURES
tional green building measures for newly constructed nonresidential buildings as well as additions and alterations. In order to meet one of the tier levels designers, builders or property owners are required to incorporate additional green building measures necessary to meet the threshold of each level. Refer to the provisions in Section 301.3 for nonresidential additions and alterations scope and application.
A5.601.2 CALGreen Tier 1
A5.601.2.1 Prerequisites. To achieve CALGreen tier status, a project must meet all of the mandatory measures in Chapter 5 and, in addition, meet the provisions of this section.
A5.601.2.2 Energy performance. For the purposes of mandatory energy efficiency standards in this code, the California Energy Commission will continue to adopt mandatory standards.
A5.601.2.3 Tier 1. Comply with the energy efficiency requirements in Section A5.203.1.1 and Section A5.203.1.2.1.
A5.601.2.4 Voluntary measures for Tier 1. In addition to the provisions of Sections A5.601.2.1 and A5.601.2.3 above, compliance with the following voluntary measures from Appendix A5 is required for Tier 1:
- From Division A5.1, a. Comply with the designated parking requirements for high-efficiency vehicles for a minimum of 35 percent of parking capacity per Section A5.106.5.1. b. Electric vehicle (EV) charging [N] and Table A5.106.5.3.1 w/ footnotes. c. Comply with thermal emittance, solar reflectance or SRI values for cool roofs in Section A5.106.11.2 and Table A5.106.11.2.2. [1]
d. Comply with one elective measure selected from this division. 2. From Division A5.2 comply with ONE of the following:
Outdoor lighting as described in A5.203.1.1.1.
Service water heating in restaurants as described in A5.203.1.1.2.
Warehouse Dock Seal Doors A5.203.1.1.3.
Daylight Design Power Adjustments 5.203.1.1.4.
Exhaust Air Heat Recovery A5.203.1.1.5.
From Division A5.3,
a. Comply with the 12-percent reduction for indoor potable water use in Section A5.303.2.3.1. b. Comply with one elective measure selected from this division.
- From Division A5.4,
CALGreen § 304.8 Medium relevance — show source text
Exception: Area of the building footprint is excluded from the calculation.
A5.304.8 Graywater irrigation system. Install a graywater collection system for onsite subsurface irrigation using graywater collected from bathtubs, showers, bathroom wash basins and laundry water. See California Plumbing Code.
SECTION A5.305—WATER REUSE
A5.305.1 Nonpotable water systems. Nonpotable water systems for indoor and outdoor use shall comply with the current edition of the California Plumbing Code.
A5.305.2 Irrigation systems. Irrigation systems regulated by a local water efficient landscape ordinance or by the California Department of Water Resources Model Water Efficient Landscape Ordinance (MWELO) shall use recycled water.
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APPENDIX A5-22 2025 CALIFORNIA GREEN BUILDING STANDARDS CODE
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CALIFORNIA GREEN BUILDING STANDARDS CODE – MATRIX ADOPTION TABLE
APPENDIX A5 – NONRESIDENTIAL VOLUNTARY MEASURES
DIVISION A5.4 – MATERIAL CONSERVATION AND RESOURCE EFFICIENCY
(Matrix Adoption Tables are nonregulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)
Adopting agency BSC BSC-
CGSFM HCD Col6 Col7 DSA Col9 OSHPD Col11 Col12 Col13 Col14 Col15 BSCC DPH AGR DWR CEC CA SL SLC Adopting agency BSC BSC-
CGSFM 1 2 1/AC AC SS 1 1R 2 3 4 5 5 5 5 5 5 5 5 5 Adopt entire CA chapter X Adopt entire chapter as
amended (amended
sections listed below)Adopt only those sections
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A5 NONRESIDENTIAL VOLUNTARY MEASURES
DIVISION A5.4 – MATERIAL CONSERVATION AND RESOURCE EFFICIENCY
SECTION A5.401—GENERAL
CALGreen § 303.5 Medium relevance — show source text
Where approved, nonwater urinals with drain cleansing action (formerly hybrid urinals), as defined in Chapter 2, shall be considered nonwater urinals.
A4.303.5 Hot water recirculation systems. One- and two-family dwellings shall be equipped with a demand hot water recirculation system, as defined in Chapter 2. The demand hot water recirculation system shall be installed in accordance with the California Plumbing Code, California Energy Code and the manufacturer’s installation instructions.
SECTION A4.304—OUTDOOR WATER USE
A4.304.1 Rainwater catchment systems. An approved rainwater catchment system is designed and installed to use rainwater generated by at least 65 percent of the available roof area. Rainwater catchment systems shall be designed and installed in accordance with the California Plumbing Code.
A4.304.2 Potable water elimination. When landscaping is provided and as allowed by local ordinance, a water efficient landscape irrigation design that eliminates the use of potable water beyond the initial requirements for plant installation and establishment shall be provided. Methods used to accomplish the requirements of this section shall comply with the requirements of the California Building Standards Code and shall include, but not be limited to, the following:
- Use of captured rainwater.
- Use of recycled water.
- Water treated for irrigation purposes and conveyed by a water district or public entity.
- Use of graywater.
- Use of drought tolerant plants.
A4.304.3 Landscape water meters. For new water service connections, landscaped irrigated areas less than 5,000 square feet shall be provided with separate submeters or metering devices for outdoor potable water use.
SECTION A4.305 —WATER REUSE SYSTEMS
A4.305.1 Graywater. Alternative plumbing piping is installed to permit the discharge from the clothes washer or other fixtures to be used for an irrigation system in compliance with the California Plumbing Code.
A4.305.2 Recycled water piping. Based on projected availability, dual water piping is installed for future use of recycled water at the following locations:
- Interior piping for the use of recycled water is installed to serve all water closets, urinals and floor drains.
- Exterior piping is installed to transport recycled water from the point of connection to the structure. Recycled water systems shall be designed and installed in accordance with the California Plumbing Code.
A4.305.3 Recycled water for landscape irrigation. Recycled water is used for landscape irrigation.
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APPENDIX A4 — RESIDENTIAL VOLUNTARY MEASURES
SECTION A4.306 —INNOVATIVE CONCEPTS AND LOCAL ENVIRONMENTAL CONDITIONS
A4.306.1 Innovative concepts and local environmental conditions. The provisions of this code are not intended to prevent the use of any alternate material, appliance, installation, device, arrangement, method, design or method of construction not specifically prescribed by this code. This code does not limit the authority of city, county, or city and county government to make necessary changes to the provisions contained in this code pursuant to Section 101.7.1.
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CALGreen § 504.4.8 Medium relevance — show source text
A5.504.4.8
Product GWP Limits Table 5.409.3
Referenced Organizations and Standards Chapter 6 Renewable Energy A5.211
Site Development 4.106, 5.106, A4,106, A5.106 Bicycle parking and changing rooms 5.106.4, A5.106.4.3, Table A5.106.4.3 Bird friendly building design A5.107 Building orientation Appendix A6.1 (OSHPD), A5.106.9 Designated parking for clean air vehicles A5.106.5.1 Exterior wall shading A5.106.7 Grading and paving 4.106.3, 5.106.10 Heat island effect – cool roof Tables A4.106.5(1) – (4), A5.106.11.2, Table
A5.106.11.2 Heat island effect – hardscape alternatives A5.106.11, A5.106.11.1 Landscape design A4.106.3 Light pollution reduction 5.106.8 Low impact development A5.106.3 Reduce parking capacity A5.106.6 Shade trees 5.106.12, A5.106.11.3 Soil analysis and protection A4.106.2 Storm water management A5.106.2 Water permeable surfaces A4.106.4 Site Preservation A4.104, A5.104 Reduce development footprint and optimize open space A5.104.1 Site Selection A4.103, A5.103 Brownfield, greyfield or infill site development A5.103.2 Community connectivity A4.103.2, A5.103.1
Voluntary Measures 301.1, 306 Voluntary Tiers 304, 305, 306, A4.601, A5.601
Water Resistance and Moisture Management 5.407, 5.505, A4.407, Appendix A6.1 (OSHPD) A5.407 Moisture control 4.505, 5.407.2, 5.505, Appendix A6.1 (OSHPD) A5.407.9, Appendix A6.1 (OSHPD) A5.505.2 Weather protection 5.407.1, A5.407.3
Water Reuse Systems A4.305 Graywater A4.305.1, A5.304.8 Recycled water for landscape irrigation A4.305.3 Recycled water piping A4.305.2 Water Use, Indoor 4.303, 5.303, A4.303, A5.203
Appliances A4.303.3, A5.303.3, Appendix A6.1 (OSHPD) A5.210 Dual plumbing A5.303.5 Fixture flow rates 4.303.1, Table A5.303.2.3.1, 5.303.2.3.1, A4.303 Kitchen faucets and dishwashers
A4.303.1
Meters 4.303.2, 5.303.1 Multiple showerheads serving one shower 4.303.1.3.2, 5.303.3.3.2 Nonwater urinals and waterless toilets
CALGreen § 303.2.3.3 Medium relevance — show source text
A5.303.2.3.3
Wastewater reduction 5.303.4
Water Use Baseline Table A5.303.2.2
Water Use, Outdoor 4.304, 5.304, A4.304, A5.304
Graywater irrigation system A5.304.8 Low-water consumption irrigation system A4.304.1 Outdoor potable water meters A4.304.3, A5.304.2 Potable water elimination A4.304.2 Previously developed sites A5.304.7 Rainwater or stormwater collection systems A4.304.1 Restoration of areas disturbed by construction A5.304.6 Worksheet Baseline Water Use Chapter 8, (WS-1) 12%, 20% or 25% Reduction Water Use Calculation Table Chapter 8, (WS-2) Building Reuse Chapter 8, (WS-3) Whole Building Life Cycle Assessment 5.409.2, Chapter 8, (WS-4) Product GWP Compliance— Prescriptive Path 5.409.3, Chapter 8, (WS-5) Building Reuse Tier 1 and Tier 2 Chapter 8, (WS-6) Whole Building Life Cycle Assessment A5.409.2, Chapter 8, (WS-7) Product GWP Compliance— Prescriptive Path A5.409.3, Chapter 8, (WS-8) Whole Building Life Cycle Assessment 5.409.2, A5.409.2, Chapter 8, (WS-9)
INDEX-2 2025 CALIFORNIA GREEN BUILDING STANDARDS CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
HISTORY NOTE APPENDIX
2025 California Green Building Standards Code California Code of Regulations, Title 24, Part 11
HISTORY:
For prior history, see the History Note Appendix to the California Green Building Standards Code, 2022 Edition, effective January 1, 2023.
- (BSC 03/24, HCD 04/24, DSA-SS 03/24, CEC 02/24)—Repeal the 2022 adoption of the California Green Building Standards Code, CCR Title 24, Part 11 and adopt the 2025 California Green Building Standards Code . Approved by the California Building Standards Commission on December 17, 2024, filed with the Secretary of State on January 10, 2025, and effective on January 1, 2026.
2025 CALIFORNIA GREEN BUILDING STANDARDS CODE HIST-1
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
California Green Building Standards Code (CALGreen) Medium relevance — show source text
; 2′6″ C.R.S. with 1″ cover on
both top and bottom flanges; 12′ span
simply supported.|115 psf|29 min|||7|1, 5,
13|1/4| |F/C-6-RC-31|6″|6″ deep (3450 psi) concrete deck; 4″ ×
13/4″ × 5 lbs R.S.J.; 2′6″ C.R.S. with 1″ cover
on both top and bottom flanges; 12′ span
simply supported.|25 psf|3 hrs
35 min|||7|1, 2|31/2| |F/C-6-RC-32|6″|6″ deep (4460 psi) concrete deck; 4″ ×
13/4″ × 5 lbs R.S.J.; 2′ C.R.S. with 1″ cover
on both top and bottom flanges; 12′ span
simply supported.|60 psf|4 hrs
30 min|||7|1, 10|41/2| |F/C-6-RC-33|6″|6″ deep (4360 psi) concrete deck; 4″ × 13/4″
× 5 lbs R.S.J.; 2′ C.R.S. with 1″ cover on
both top and bottom flanges; 13′1″ span
restrained.|60 psf|2 hrs|||7|1, 3|2| |F/C-6-RC-34|61/4″|61/4″ thick; 43/4″ (5120 psi) concrete core;
1″ T&G board flooring;1/2″ plaster under-
coat; 4″ × 3″ × 10 lbs R.S.J.; 3′ C.R.S. flush
with top surface concrete; 12′ span simply
supported; 2″ × 1′3″ clinker concrete
insert.|100 psf|4 hrs|||7|1, 7|4| |F/C-6-RC-35|61/4″|43/4″ (3600 psi) concrete core; 1″ T&G
board flooring;1/2″ plaster undercoat; 4″ ×
3″ × 10 lbs R.S.J.; 3′ C.R.S. flush with top
surface concrete; 12′ span simply
supported; 2″ × 1′3″ clinker concrete
insert.|100 psf|2 hrs
30 min|||7|1, 5|21/2| |F/C-6-RC-36|61/4″|43/4″ (2800 psi) concrete core; 1″ T&G
board flooring;1/2″ plaster undercoat; 4″ ×
3″ × 10 lbs R.S.J.; 3′ C.R.S.CALGreen § 0.0929 Medium relevance — show source text
For SI units: 1 square foot = 0.0929 m [2], 1 gallon per day = 0.000043 L/s
1504.4 Groundwater Level. No excavation for an irrigation field, disposal field, or mulch basin shall extend within 3 feet (914 mm) vertical of the highest known seasonal groundwater level, nor to a depth where gray water contaminates the groundwater or surface water. The applicant shall supply evidence of groundwater depth to the satisfaction of the Authority Having Jurisdiction.
Note: The absence of groundwater in a test hole three (3) vertical feet (915 mm) below the deepest irrigation or dis- posal point shall be sufficient to satisfy this section unless seasonal high groundwater levels have been documented to rise to within this area.
1504.5 Irrigation, Disposal Field and Mulch Basin Construction. Irrigation fields, disposal fields and mulch basins used in gray water systems shall comply with this sec- tion. Gray water systems may contain either an irrigation field or a disposal field or a combination of both. This section is not intended to prevent the use of other methods of gray water irrigation or disposal approved by the Enforcing Agency.
TABLE 1504.2
DESIGN OF SIX TYPICAL SOILS
For SI units: 1 square foot = 0.0929 m [2], 1 gallon per day = 0.000043 L/s
316 2025 CALIFORNIA PLUMBING CODE
), 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
[BSC-CG] Irrigation design shall be verified in accor- dance with the California Green Building Standards Code (CALGreen), Chapter 5, Division 5.3.
[HCD 1] Irrigation design shall be verified in accor- dance with the California Green Building Standards Code (CALGreen), Chapter 4, Division 4.3.
1504.5.1 Mulch Basin. A mulch basin may be used as an irrigation or disposal field. Mulch basins shall be sized in accordance with Table 1504.2 and of sufficient depth, length and width to prevent ponding or runoff dur- ing the gray water surge of a clothes washer, bathtub or shower. Mulch must be replenished as required due to decomposition of organic matter. Mulch basins will require periodic maintenance, reshaping or removal of dirt to maintain surge capacity and to accommodate plant growth and prevent ponding or runoff.
1504.5.2 Irrigation Field. The provisions of this sec- tion are not intended to prevent the use of any appropri- ate material, appliance, installation, device, design or method of construction. If an alternate design is not available, the following provisions may be used as guid- ance in the design of a gray water irrigation field:
Frequently asked questions
What does the 12% target in § A5.303.2.3.1 actually mean?
It is the Tier 1 indoor potable water reduction percentage you must achieve under Appendix A5’s performance path when you select that measure; compute actual savings against the baseline determined using Table A5.303.2.2.
Is graywater irrigation allowed as spray irrigation under § A5.304.8?
No. § A5.304.8 specifies onsite subsurface irrigation using graywater from the listed fixtures; for permitted application methods and detailed design you must follow the California Plumbing Code.
Is Appendix A5 mandatory statewide?
No. Appendix A5 is a set of voluntary measures unless a local jurisdiction adopts them. Confirm local adoption before assuming Appendix A5 requirements apply.
Who specifies the technical details (setbacks, mulch basin design, groundwater separation) for graywater systems?
The California Plumbing Code contains the technical and health/safety requirements for graywater systems; § A5.305.1 in CALGreen requires compliance with that code.
Can graywater collected under § A5.304.8 be used indoors?
CALGreen’s A5 text directs graywater for onsite subsurface irrigation; any indoor reuse or alternate nonpotable use must comply with the California Plumbing Code and the nonpotable system rules in § A5.305.1.
More in California Green Building Standards Code (CALGreen)
- Administration (Chapter 1)
- Nonresidential Voluntary Measures (Appendix A5 — divisions A5.1–A5.6, electives & verification)
- Residential Mandatory Measures — Planning & Design; Energy; Water; Materials; Environmental Quality (Chapter 4)
- Definitions (Chapter 2)
- Voluntary Standards for Health Facilities (Appendix A6 / OSHPD guidance)
- Green Building – scope, mixed occupancies, phased projects (Chapter 3)
- Residential Voluntary Measures (Appendix A4 — divisions A4.1–A4.6, tiers & model ordinance)
- Nonresidential Mandatory Measures — Planning & Design; Energy; Water; Materials; Environmental Quality (Chapter 5)
- Compliance verification, construction documents & checklists (Section 102, Chapter 7, Appendix checklists)
- Referenced Organizations and Standards (Chapter 6)
- Voluntary Tiers and CALGreen Tier 1 / Tier 2 (performance tiers, thresholds)
- Installer and Special Inspector Qualifications (Chapter 7)
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Recycled content, construction & demolition waste reduction and life‑cycle assessment options
Irrigation, recycled water and landscape/nonpotable requirements
Efficient framing (wood & steel) and advanced framing techniques
Water Efficiency & Material Conservation (Divisions A5.3–A5.4)
California Green Building Standards Code (CALGreen)