CPC · California Plumbing Code

When can I use engineered sizing or Appendix D sizing methods?

Q: When does Appendix D NOT apply?

Appendix D provisions are not mandatory unless your state agency or local jurisdiction adopts them; always confirm with the Authority Having Jurisdiction before relying on Appendix D for code compliance ( § D101.1 ) .

Q: Where do I get the rainfall value for my city?

Use the gpm per ft² value in Table D 101.1 for your city (or a higher locally established value) when using the Appendix D flow‑rate method ( § D102.1 ) file.

Q: Do siphonic drains require anything special?

Yes — siphonic roof drainage systems must be designed to ASPE/ANSI 45 and siphonic drains must comply with ASME A112.6.9 (see § 1106.2 and § 1106.3 ) .

Q: What tables do I use to convert required gpm into pipe sizes?

Use Table 1103.1 and Table 1103.2 (Chapter 11). Appendix D references those tables for required pipe sizes after you compute flow or allowable roof area ( § D102.1 ) file.

Short answer for a homeowner: The CPC lets you either use a table-based Appendix D method (use local rainfall values from Table D101.1) or hire an engineer to size the storm system. Appendix D is optional unless your city requires it, while an engineered system must be prepared and stamped by a registered design professional and approved by the local authority (see § 1106.1 and Appendix D sections) file.

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Last reviewed: July 6, 2026

What the code requires

The California Plumbing Code permits the use of an engineered storm drainage system — i.e., sizing determined by accepted engineering practice — when the system is designed and stamped by a registered design professional and approved by the authority having jurisdiction (see § 1106.1) .
Separately, Appendix D provides a prescriptive, table-based method to size storm drainage by rainfall rates or roof area; those appendix provisions are not mandatory unless adopted or referenced by the enforcing agency (see § D101.1 and § D102.1) .

The single most important rule: If you choose engineered sizing the design must be prepared and certified by a registered design professional and approved by the AHJ (see § 1106.1) .

Requirements in detail

When engineered sizing is allowed and what it requires

The Code allows the design and sizing of storm drainage systems to be determined by accepted engineering practices (bold: § 1106.1) — the engineered design must be prepared by a registered design professional and approved in accordance with the code (the text refers to approval per Section 301.5) .
Specific engineered systems called out:
- Siphonic roof drainage systems must comply with ASPE/ANSI 45 (§ 1106.2) .
- Siphonic roof drains must meet ASME A112.6.9 (§ 1106.3) .

When Appendix D methods may be used

Appendix D provides permitted, table-driven methods for sizing storm drainage:
- Use the gallons per minute per square foot value from Table D 101.1 for your locality, multiply by the roof area to get the gpm required at each inlet (method in § D102.1) .
- Alternatively, use the allowable roof area / pipe-size tables (Tables 1103.1 and 1103.2) and interpolate between rainfall-rate columns as permitted in § D103.1 file.
Important note: Appendix D is advisory unless your local jurisdiction adopts it (see § D101.1) .

Decision‑relevant numbers and where to find them

Decision item	Typical value / threshold you need	How used	Code Reference
Who may prepare an engineered design	Registered design professional	Required sign-off for engineered systems	§ 1106.1
Mandatory adoption of appendix methods	Appendix D provisions are not mandatory unless adopted locally	Check AHJ before using Appendix D as code compliance	§ D101.1
Sizing method (flow-rate)	gpm per ft² from Table D 101.1 (local city value)	Multiply by roof area to get gpm per inlet (D102.1)	§ D102.1 and Table D 101.1 file
Sizing method (roof-area tables)	Tables 1103.1 / 1103.2 list allowable area per pipe size at standard rainfall rates	Use/ interpolate per § D103.1	§ D103.1; Tables 1103.1 / 1103.2 file
Siphonic system standard	ASPE/ANSI 45 (design); ASME A112.6.9 (products)	Required compliance for siphonic designs	§ 1106.2 / § 1106.3

Exceptions & special cases

Appendix D is non-mandatory unless your state agency or local jurisdiction adopts it; you must confirm with the Authority Having Jurisdiction before relying on Appendix D as the compliance method (§ D101.1) .
If you select an engineered approach, the design does not follow the appendix/tables — it follows accepted engineering practices and must be approved and documented per § 1106.1 (and approval requirements referenced in the code) .
Siphonic systems are a special engineered class with their own standards: ASPE/ANSI 45 and ASME A112.6.9 (see § 1106.2 and § 1106.3) .

Common mistakes

Assuming Appendix D is automatically acceptable — Appendix D is permissive guidance and is not mandatory unless adopted; using it without AHJ acceptance is a common compliance error (§ D101.1) .
Choosing engineered sizing but failing to have the design prepared and stamped by a registered design professional and approved by the AHJ (violates § 1106.1) .
Using the wrong rainfall rate: Appendix D requires you to use the local gpm/ft² value from Table D 101.1 — picking the wrong city or ignoring local amendments leads to undersized systems (§ D102.1) file.
Forgetting to add flows from multiple inlets or to read the correct column (rainfall rate) in Tables 1103.1 / 1103.2 when converting required gpm to pipe sizes (§ D102.1 and Tables 1103.1/1103.2) file.

Worked example — Appendix D flow-rate method (use as‑allowed)

Scenario: A single roof area of 3,000 ft² drains to one inlet in Los Angeles (use Table D 101.1 local value).

Find local rainfall gpm/ft² from Table D 101.1: Los Angeles = 2.0 in/h, = 0.021 gpm/ft² (Table D 101.1) .
Calculate required inlet flow (D102.1): required gpm = 0.021 gpm/ft² × 3,000 ft² = 63 gpm file.
Select a pipe size from the horizontal piping tables (Table 1103.2 or 1103.1) using your pipe slope. Example: at 1/2 inch per foot slope, 3‑inch horizontal rainwater pipe capacity ≈ 68 gpm (table value), which is greater than 63 gpm, so a 3‑inch horizontal conductor would be acceptable by the tables (refer to Tables 1103.1/1103.2) file.
Important: If you instead elect an engineered design for the same roof, the system must be prepared and stamped by a registered design professional and approved by the AHJ under § 1106.1 .

(Notes: the example uses values and tables from Appendix D and Chapter 11; if your AHJ requires a different rainfall basis or requires engineered design, follow § 1106.1 and local requirements) file.

Related provisions (quick links)

Engineered storm drainage design permission and professional responsibility — § 1106.1
Siphonic roof drainage design standard — § 1106.2
Siphonic roof drain product standard — § 1106.3
Appendix D applicability and non‑mandatory status — § D101.1
Appendix D sizing by flow rate (gpm/ft²) — § D102.1
Appendix D sizing by roof area and interpolation guidance — § D103.1
Roof drainage design basis (60‑minute, 100‑year storm) — § 1101.12.1
Tables for converting gpm → pipe size: Table 1103.1 and Table 1103.2 (Chapter 11 tables) file

Code references

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

CPC § 2025 Medium relevance — show source text
Appendix A Recommended Rules for Sizing the Water Supply System.

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

Appendix B Explanatory Notes on Combination Waste and Vent Systems.

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

Appendix C Alternate Plumbing Systems.

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

Appendix D Sizing Storm Water Drainage Systems.

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

2025 CALIFORNIA PLUMBING CODE xvii

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FORMAT OF THE UNIFORM PLUMBING CODE

Appendix E Manufactured/Mobile Home Parks and Recreational Vehicle Parks.

The provisions of this appendix apply to the plumbing and drainage systems of mobile home and recreational vehicle parks. These provisions also apply to the use, maintenance, and installation for supplying fuel gas, water, electricity, and disposal of sewage from accessory buildings or structures, and building components.

Appendix F Firefighter Breathing Air Replenishment Systems.

Appendix F provides guidance on installing firefighter breathing air replenishment systems. System components include outside fire department connection panel, interior air fill panel or station, interconnected piping distribution system and pressure monitoring switch. Fire departments access the system through an outside connection panel and are able to pump air into the system. The firefighters inside the structure access the system at fill stations that are found throughout the building. The piping distribution system is made from stainless tubing or other approved materials. It delivers compressed air to the building’s interior air-fill stations and interior air-fill panels. The tubing also acts as a conduit in the interior of the building between the outside connection panel and the air storage system. If the system becomes over-pressurized, the air monitoring system also acts as a pressure relief. A system isolation valve is placed alongside each interior air fill station and interior air fill panel to isolate the system.

Appendix G Sizing of Venting Systems.

Appendix G provides added information on the sizing of gas vents. This appendix is useful to the end user for the proper sizing of venting systems. A series of examples are given that show how to use the tables and other requirements of Chapter 5.

Appendix H Private Sewage Disposal Systems.
CPC § 613.0 Medium relevance — show source text
Notes: 1 Installation of a kitchen sink and dishwasher, laundry sink, and automatic clothes washer permitted without additional size increase. 2 An additional water closet and lavatory permitted. 3 Over four bathroom groups, the softener size shall be engineered for the specific installation. 4 See also Appendix A, Recommended Rules for Sizing the Water Supply System, and Appendix C, Alternate Plumbing Systems, for alternate methods of sizing water supply systems.

613.0 Domestic Hot-Water Distribution Systems for Health Facilities and Clinics. [OSHPD 1, 2, 3, 4 & 5]

613.1 The domestic water-heating equipment and distribu- tion systems shall supply water at the temperature and amounts shown in Table 613.1. Where the system is designed by a mechanical engineer, appropriate diversity factors may be utilized.

TABLE 613.1

[OSHPD 1, 2, 3, 4 & 5] HOT WATER USE

Col1 CLINICAL DIETARY1 LAUNDRY2

Liter/Hour/Bed 11.9 7.2 7.6

Gallons/Hour/Bed 3 2 2

Temperature °C 41-49.0 49.03 71.0

Temperature °F 105-120.0 120.03 160.0

1 Rinse water temperature at warewasher or potsinks shall be 180°F (82°C) unless a chemical disinfection is provided.

2 The required temperature of 160°F (71°C) in the laundry is that meas- ure in the washing machine and shall be supplied so that the tempera- ture may be maintained over the entire wash and rinse period.

Exception: A lower water temperature of 140°F (60°C) may be utilized, pro- vided linens are subsequently passed through a tumbler dryer at 180°F (82°C) or a flatwork ironer at 300°F (149°C).

3 Dietary hot water temperature shall meet minimum temperature require- ments at the point of use per the health authority.

613.2 At least two pieces of hot-water-heating equipment shall be provided to supply hot water for dishwashing and minimum patient services such as handwashing and bathing. The arrangement of water-heating equipment shall be based on the capacity and capability of the equipment to provide the required hot water during periods of breakdown or mainte- nance of any one water heater. Booster heaters for 125°F to 180°F (52°C to 82°C) water are acceptable as a second piece of equipment for dishwashing. Where storage tanks are sepa- rate from the water heater, at least two independent storage tanks shall be provided. Storage water heaters and hot-water storage tanks shall be maintained at 140°F (60°C) or above.

Exception: A single piece of hot-water-heating equipment shall be permitted, subject to the Authority Having Jurisdiction, for primary care and non-specialty clinics where the equipment is limited to the service of handwashing fixtures.
CPC § 2.25 Medium relevance — show source text
00|2.25|0.70|DR|3.70|1.05|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|33 mil cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|16|3.85|1.45|DR|DR|3.40|DR|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|33 mil cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|24|3.40|DR|DR|DR|2.70|DR|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#8 Screw|Steel thick-
ness plus 3
threads|12|3.00|1.80|DR|DR|3.00|0.65|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#8 Screw|Steel thick-
ness plus 3
threads|16|3.00|1.00|DR|DR|2.85|DR|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#8 Screw|Steel thick-
ness plus 3
threads|24|2.85|DR|DR|DR|2.20|DR|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|12|4.00|3.85|2.80|1.80|4.00|3.05|1.50|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|16|4.00|3.30|1.95|0.60|4.00|2.25|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|24|4.00|2.25|DR|DR|4.00|0.65|DR|DR| |For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa, 1 pound per square inch = 0.00689 MPa.
DR = Design Required, o.c. = on center.
a. Wood furring shall be spruce-pine-fir or any softwood species with a specific gravity of 0.42 or greater.
CPC § 1701.1 Medium relevance — show source text
Chapter 16 Nonpotable Rainwater Catchment Systems.

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

Chapter 17 Referenced Standards.

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

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

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

Appendix A Recommended Rules for Sizing the Water Supply System.

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

Appendix B Explanatory Notes on Combination Waste and Vent Systems.

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

Appendix C Alternate Plumbing Systems.

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

Appendix D Sizing Storm Water Drainage Systems.

Appendix D provides general guidelines for the sizing of stormwater drainage systems. There are two pieces of information that must always be a given. They are the roof size and the rate of rainfall f
CPC § 1101.16 Medium relevance — show source text
1101.16 Leaders, Conductors, and

Connections . . . . . . . . . . . . . . . . .207

1102.0 Roof Drains . . . . . . . . . . . . . . . . . .207

1102.1 Applications . . . . . . . . . . . . . . . . .207

1102.2 Dome Strainers Required . . . . . . .207

1102.3 Roof Drain Flashings . . . . . . . . . .207

1103.0 Size of Leaders, Conductors,

and Storm Drains . . . . . . . . . . . . .207

1103.1 Vertical Conductors and

Leaders . . . . . . . . . . . . . . . . . . . . .207

1103.2 Size of Horizontal Storm

Drains and Sewers . . . . . . . . . . . .207

1103.3 Size of Roof Gutters . . . . . . . . . . .207

1103.4 Side Walls Draining onto a Roof . . . . . . . . . . . . . . . . . .207

Table 1103.1 Sizing Roof Drains, Leaders, and Vertical Rainwater Piping . . .208

1104.0 Values for Continuous Flow . . . . .208

1104.1 General . . . . . . . . . . . . . . . . . . . . .208

1105.0 Controlled-Flow Roof

Drainage . . . . . . . . . . . . . . . . . . . .208

1105.1 Application . . . . . . . . . . . . . . . . . .208

Table 1105.1(1) Controlled-Flow Maximum Roof Water Depth . . . . . . . . . . . . .209

Table 1105.1(2) Distance of Scupper Bottoms Above Roof . . . . . . . . . . . . . . . . . .209

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TABLE OF CONTENTS

1105.2 Setback Roofs . . . . . . . . . . . . . . .209

1106.0 Engineered Storm Drainage System . . . . . . . . . . . . . . . . . . . . .209

1106.1 General . . . . . . . . . . . . . . . . . . . . .209

1106.2 Siphonic Roof Drainage Systems . . . . . . . . . . . . . . . . . . . .209

1106.3 Siphonic Roof Drains . . . . . . . . . .209

1107.0 Testing . . . . . . . . . . . . . . . . . . . . .209

1107.1 Testing Required . . . . . . . . . . . . .209

1107.2 Methods of Testing Storm Drainage Systems . . . . . . . . . . . .209

Table 1103.2 Sizing of Horizontal Rainwater Piping . . . . . . . . . . . . .210

Table 1103.3 Size of Gutters . . . . . . . . . . . . . . .211
CPC § 25.4 Medium relevance — show source text
The interior and exterior cob faces shall be permitted to be unfinished or receive any plaster finish allowed by this appendix.
d.
Cob walls with more than one density shall be built with heavier densities below lighter densities.
e.
Minimum cob wall thickness shall be whichever is greater in Tables BK105.3, BK106.11(1) and BK108.1.
f.
Wall thicknesses less than 10 inches require an engineered design.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound = 0.45 kg, 1 pound per cubic foot = 16.02 kg/m3.
a.
Density is to be measured at equilibrium moisture content. Average wall density shall be within ±5 pcf of the tabulated value.
b.
Requires an approved engineered design per Section BK106.6.
c.
Cob thickness only. The interior and exterior cob faces shall be permitted to be unfinished or receive any plaster finish allowed by this appendix.
d.
Cob walls with more than one density shall be built with heavier densities below lighter densities.
e.
Minimum cob wall thickness shall be whichever is greater in Tables BK105.3, BK106.11(1) and BK108.1.
f.
Wall thicknesses less than 10 inches require an engineered design.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound = 0.45 kg, 1 pound per cubic foot = 16.02 kg/m3.
a.
Density is to be measured at equilibrium moisture content. Average wall density shall be within ±5 pcf of the tabulated value.
b.
Requires an approved engineered design per Section BK106.6.
c.
Cob thickness only. The interior and exterior cob faces shall be permitted to be unfinished or receive any plaster finish allowed by this appendix.
d.
Cob walls with more than one density shall be built with heavier densities below lighter densities.
e.
Minimum cob wall thickness shall be whichever is greater in Tables BK105.3, BK106.11(1) and BK108.1.
f.
Wall thicknesses less than 10 inches require an engineered design.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound = 0.45 kg, 1 pound per cubic foot = 16.02 kg/m3.
a.
Density is to be measured at equilibrium moisture content. Average wall density shall be within ±5 pcf of the tabulated value.
b.
Requires an approved engineered design per Section BK106.6.
c.
Cob thickness only. The interior and exterior cob faces shall be permitted to be unfinished or receive any plaster finish allowed by this appendix.
d.
Cob walls with more than one density shall be built with heavier densities below lighter densities.
e.
Minimum cob wall thickness shall be whichever is greater in Tables BK105.3, BK106.11(1) and BK108.1.
f.
Wall thicknesses less than 10 inches require an engineered design.|

BK108.2 Clearance to fireplaces and chimneys. Cob walls or other cob surfaces shall not require clearance to fireplaces and chimneys, except where clearance to noncombustibles is required by the manufacturer’s instructions.

SECTION BK109—THERMAL PERFORMANCE

**BK109.1 Thermal characteristics.
CPC § 60532-3696. Medium relevance — show source text
SAE Society of Automotive Engineers, 400 Commonwealth Drive, Warrendale, PA 15096.

TCNA Tile Council of North America, Inc. 100 Clemson Research Blvd., Anderson, SC 29625.

UL Underwriters Laboratories, Inc., 333 Pfingsten Road, Northbrook, IL 60062.

WQA Water Quality Association, 4151 Naperville Road, Lisle, IL 60532-3696.

WSC Water Systems Council, 1101 30th Street, NW, Suite 500, Washington, D.C. 20007.

2025 CALIFORNIA PLUMBING CODE 361

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APPENDICES

The appendices are intended to supplement the provisions of the installation requirements of this code. The definitions in Chapter 2 are also applicable to the appendices.

TABLE OF CONTENTS

Page Appendix A Recommended Rules for Sizing the Water Supply System...........................................................................365

Appendix B Explanatory Notes on Combination Waste and Vent Systems ......................................................................381

Appendix C Alternate Plumbing Systems..........................................................................................................................385

Appendix D Sizing Storm Water Drainage Systems..........................................................................................................395

Appendix E Manufactured/Mobile Home Parks and Recreational Vehicle Parks .............................................................405

Appendix F Firefighter Breathing Air Replenishment Systems .........................................................................................417

Appendix G Sizing of Venting Systems ............................................................................................................................423

Appendix H Private Sewage Disposal Systems ................................................................................................................435

Appendix I Installation Standards ....................................................................................................................................447

Appendix J Combination of Indoor and Outdoor Combustion and Ventilation Opening Design.......................................487

Appendix K Potable Rainwater Catchment Systems ........................................................................................................491

Appendix L Sustainable Practices ....................................................................................................................................497

Appendix M Peak Water Demand Calculator ....................................................................................................................517

Appendix N Impact of Water Temperature on the Potential for Scalding and Legionella Growth .....................................525

2025 CALIFORNIA PLUMBING CODE 363

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TABLE OF CONTENTS (continued)

Appendix O Non-Sewered Sanitation Systems .................................................................................................................531

Appendix P

Professional Qualifications.............................................................................................................................535

Appendix Q

Indoor Horticultural Facilities..........................................................................................................................539

Appendix R Tiny Houses...............................................................................
CPC § 363 Medium relevance — show source text
APPENDICES TABLE OF CONTENTS . . . . . . . .363

Appendix A Recommended Rules for Sizing the Water Supply System . . . . . . . . . . . . . . . . . . . . .365

Appendix B Explanatory Notes on Combination Waste and Vent

Systems . . . . . . . . . . . . . . . . . . . .381

Appendix C Alternate Plumbing Systems . . . .385

Appendix D Sizing Storm Water Drainage Systems . . . . . . . . . . . . . . . . . . . .395

Appendix E Manufactured/Mobile Home Parks and Recreational

Vehicle Parks . . . . . . . . . . . . . . . .405

Appendix F Firefighter Breathing Air Replenishment Systems . . . . . . . .417

Appendix G Sizing of Venting Systems . . . . . .423

Appendix H Private Sewage Disposal Systems . . . . . . . . . . . . . . . . . . . .435

Appendix I Installation Standards . . . . . . . . . .447

Appendix J Combination of Indoor and Outdoor Combustion and

Ventilation Opening Design . . . . .487

Appendix K Potable Rainwater Catchment Systems . . . . . . . . . . .491

Appendix L Sustainable Practices . . . . . . . . . .497

Appendix M Peak Water Demand Calculator . . . . . . . . . . . . . . . . . . .517

Appendix N Impact Of Water Temperature On The Potential for Scalding and Legionella Growth . . . . . . . . .525

Appendix O Non-Sewered Sanitation Systems . . . . . . . . . . . . . . . . . . . .531

Appendix P Professional Qualifications . . . . . .535

Appendix Q Indoor Horticultural Facilities . . . .539

Appendix R Tiny Houses . . . . . . . . . . . . . . . . .543

Appendix S Onsite Stormwater Treatment Systems . . . . . . . . . . . . . . . . . . . .547

USEFUL TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . .553

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . .563

HISTORY NOTE

APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . .589

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CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE

CHAPTER 1 - ADMINISTRATION

(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

CPC § 611.1 Medium relevance — show source text

WATER SUPPLY AND DISTRIBUTION

Col1	TABLE 611.1 DRINKING WATER TREATMENT UNITS	Col3	Col4
APPLICATION	RESIDENTIAL	RESIDENTIAL	COMMERCIAL
APPLICATION	POINT OF USE	POINT OF ENTRY	POINT OF ENTRY
Aesthetic Contaminant Reduction (filters)	NSF/ANSI 42	NSF/ANSI 42	ASSE 1087 and NSF/ANSI 42*
Health Related Contaminant Reduction (filters)	NSF/ANSI 53	NSF/ANSI 53	ASSE 1087 and NSF/ANSI 53*
Water Softener	–	NSF/ANSI 44	ASSE 1087
Ultraviolet Water Treatment	NSF/ANSI 55	NSF/ANSI 55	ASSE 1087
Reverse Osmosis	NSF/ANSI 58	NSF/ANSI/CAN 61	ASSE 1087
Distillation	NSF/ANSI 62	NSF/ANSI 62	ASSE 1087

 - Required for commercial modular systems only.

TABLE 611.4 SIZING OF RESIDENTIAL WATER SOFTENERS [4]

REQUIRED SIZE OF SOFTENER CONNECTION (inches)	NUMBER OF BATHROOM GROUPS SERVED1
3⁄4	up to 22
1	up to 43

For SI units: 1 inch = 25 mm

Notes: 1 Installation of a kitchen sink and dishwasher, laundry sink, and automatic clothes washer permitted without additional size increase. 2 An additional water closet and lavatory permitted. 3 Over four bathroom groups, the softener size shall be engineered for the specific installation. 4 See also Appendix A, Recommended Rules for Sizing the Water Supply System, and Appendix C, Alternate Plumbing Systems, for alternate methods of sizing water supply systems.

613.0 Domestic Hot-Water Distribution Systems for Health Facilities and Clinics. [OSHPD 1, 2, 3, 4 & 5]

613.1 The domestic water-heating equipment and distribu- tion systems shall supply water at the temperature and amounts shown in Table 613.1. Where the system is designed by a mechanical engineer, appropriate diversity factors may be utilized.

TABLE 613.1

[OSHPD 1, 2, 3, 4 & 5] HOT WATER USE

Col1	CLINICAL	DIETARY1	LAUNDRY2
Liter/Hour/Bed	11.9	7.2	7.6
Gallons/Hour/Bed	3	2	2
Temperature °C	41-49.0	49.03	71.0
Temperature °F	105-120.0	120.03	160.0

1 Rinse water temperature at warewasher or potsinks shall be 180°F (82°C) unless a chemical disinfection is provided.

CPC § 1.11.0. Medium relevance — show source text
This state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.

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APPENDIX G

SIZING OF VENTING SYSTEMS

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

G 101.0 General.

G 101.1 Applicability. This appendix provides general guidelines for sizing venting systems serving appliances equipped with draft hoods, Category I appliances, and appliances listed for use with Type B vents.

Table 510.1.2(1) is used when sizing a Type B double-wall gas vent connected directly to the appliance.

Note: The appliance can be either Category I draft hood-equipped or fanassisted type. FIGURE G 101.2(1) TYPE B DOUBLE-WALL VENT SYSTEM SERVING A SINGLE APPLIANCE WITH A TYPE B DOUBLE-WALL VENT

[NFPA 54: FIGURE F.1(a)]

Table 510.1.2(2) is used when sizing a single-wall metal vent connector attached to a Type B double-wall gas vent.

Note: The appliance can be either Category I draft hood-equipped or fanassisted type. FIGURE G 101.2(2) TYPE B DOUBLE-WALL VENT SYSTEM SERVING A SINGLE APPLIANCE WITH A SINGLE-WALL METAL VENT CONNECTOR

[NFPA 54: FIGURE F.1(b)]

G 101.2 Examples Using Single Appliance Venting Tables. See Figure G 101.2(1) through Figure G 101.2(14).

[NFPA 54:F.1]

Table 510.1.2(3) is used when sizing a Type B double-wall gas vent connector attached to a tile-lined masonry chimney.

Notes:
1. A is the equivalent cross-sectional area of the tile liner.
2. The appliance can be either Category I draft hood-equipped or fan-assisted type. FIGURE G 101.2(3) VENT SYSTEM SERVING A SINGLE APPLIANCE WITH A MASONRY CHIMNEY AND A TYPE B DOUBLE-WALL VENT CONNECTOR
[NFPA 54: FIGURE F.1(c)]

Table 510.1.2(4) is used when sizing a single-wall vent connector attached to a tile-lined masonry chimney.

Notes:
1. A is the equivalent cross-sectional area of the tile liner.
2. The appliance can be either Category I draft hood-equipped or fan-assisted type. FIGURE G 101.2(4) VENT SYSTEM SERVING A SINGLE APPLIANCE USING A MASONRY CHIMNEY AND A SINGLE-WALL METAL VENT CONNECTOR
[NFPA 54: FIGURE F.1(d)]
CPC § 4.1 Medium relevance — show source text
- 100°F
  (16°C-38°C)|1 h|6 h|2 h|12 h|6 h|24 h| |40°F-60°F
  (4°C-16°C)|2 h|12 h|4 h|24 h|12 h|48 h| |10°F- 40°F
  (-12°C+4°C)|8 h|48 h|16 h|96 h|48 h|8 days| |*If gaps or loose fits are encountered in the system, double these cure times.|*If gaps or loose fits are encountered in the system, double these cure times.|*If gaps or loose fits are encountered in the system, double these cure times.|*If gaps or loose fits are encountered in the system, double these cure times.|*If gaps or loose fits are encountered in the system, double these cure times.|*If gaps or loose fits are encountered in the system, double these cure times.|*If gaps or loose fits are encountered in the system, double these cure times.|
2025 CALIFORNIA PLUMBING CODE 467

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IS 33

FIGURE 1

LOCATION OF THRUST BLOCKS (STANDARD AND METRIC COMBINED) A COMPARISON OF THRUST-BLOCK AREAS (See Section 4.1)

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IS 33

FIGURE 2

THRUST BLOCK BEARING AREA (See Section 5.2.2)

2025 CALIFORNIA PLUMBING CODE 469

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IS 33

Uniform Plumbing Code References for Ductile Iron and PVC Pressure Building Supply and Exterior Cold-Water Piping

The following sections of the 2024 Uniform Plumbing Code apply to ductile iron and PVC pressure building supply and exterior cold-water piping.

Chapter 3 General Regulations

309.0 Workmanship

312.0 Protection of Piping, Materials, and Struc tures

313.0 Hangers, Supports, and Anchors

314.0 Trenching, Excavation, and Backfill

Chapter 6 Water Supply and Distribution

604.0 Materials (water piping)

Table 604.1 Materials for Building Supply and Water Distribution Piping and Fittings

605.4 Ductile Iron Pipe and Joints

605.12 PVC Plastic Pipe and Joints

605.16.2 Plastic Pipe to Other Materials

609.0 Installation, Testing, Unions, and Location

Abbreviations

IAPMO International Association of Plumbing and Mechanical Officials

UPC Uniform Plumbing Code published by IAPMO

AWWA American Water Works Association

CSA Canadian Standards Association

Applicable Standards.

ASME B16.4 Gray Iron Threaded Fittings Classes 125 and 250

ASTM D1785 Poly (Vinyl Chloride) (PVC) Plastic Pipe, Schedules 40, 80, and 120

ASTM D2241 Poly (Vinyl Chloride) (PVC) Pressure-Rated Pipe (SDR Series)

CFC § J102 Medium relevance — show source text

to:

Impact-resistant drywall.
Impact-resistant glazing, such as blast or hurricane-type glass.
All types of roof and floor structural members including but not limited to post-tension concrete, bar joists, solid wood joists, rafters, trusses, cold-formed galvanized steel, I-joists and I-beams; green roof with vegetation, soil and plants.
Hazardous materials (such as explosives, chemicals, plastics).
Solar panels and DC electrical energy.
HVAC system; and smoke management system for pressurization and exhaust methods.
Other unique characteristic(s) within the building that are ranked according to a potential risk to occupants and firefighters.

J101.8 Sign classification maintenance, building information. Sign maintenance shall comply with each of the following:

Fire departments in the jurisdiction shall define the designations to be placed within the sign.
Fire departments in the jurisdiction shall conduct annual inspections to verify compliance with this section of the code and shall notify the owner, or the owner’s agent, of any required updates to the sign in accordance with fire department designations and the owner, or the owner’s agent, shall comply within 30 days.
The owner of a building shall be responsible for the maintenance and updates to the sign in accordance with fire department designations.

J101.9 Training. Jurisdictions shall train fire department personnel on Sections J101.1 through J101.8.

SECTION J102—REFERENCED STANDARDS

J102.1 General. See Table J102.1 for standards that are referenced in various sections of this appendix. Standards are listed by the standard identification with the effective date, standard title, and the section or sections of this appendix that reference the standard.

TABLE J102.1—REFERENCED STANDARDS	Col2	Col3
STANDARD ACRONYM	STANDARD NAME	SECTIONS HEREIN REFERENCED
CBC—25	California Building Code	J101.3, J101.5
NFPA 13—22	Installation of Sprinkler Systems	J101.6

2025 CALIFORNIA FIRE CODE APPENDIX J-5

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

APPENDIX J-6 2025 CALIFORNIA FIRE CODE

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

CALIFORNIA FIRE CODE – MATRIX ADOPTION TABLE

APPENDIX K – CONSTRUCTION REQUIREMENTS FOR EXISTING AMBULATORY CARE FACILITIES

(Matrix Adoption Tables are nonregulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

(Not adopted by the State Fire Marshal)

CPC § 1103.1. Medium relevance — show source text
(9) Scupper openings shall be not less than 4 inches (102 mm) high and have a width equal to the circumference of

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STORM DRAINAGE

the roof drain required for the area served, sized in accordance with Table 1103.1.

(10)Flashings shall extend above the top of the scuppers.

(11)At a wall or parapet, 45 degree (0.79 rad) cants shall be installed.

(12)Separate storm and sanitary drainage systems shall be provided within the building.

(13)Calculations for the roof drainage system shall be submitted along with the plans to the Authority Having Jurisdiction for approval.

TABLE 1105.1(1) CONTROLLED-FLOW MAXIMUM ROOF WATER DEPTH

ROOF RISE*
(inches) MAXIMUM WATER DEPTH AT
DRAIN
(inches)

Flat 3

2 4

4 5

6 6

For SI units: 1 inch = 25.4 mm
- Vertical measurement from the roof surface at the drain to the highest point of the roof surface served by the drain, ignoring a local depression immediately adjacent to the drain.
TABLE 1105.1(2) DISTANCE OF SCUPPER BOTTOMS ABOVE ROOF

ROOF RISE*
(inches) ABOVE ROOF LEVEL
AT DRAIN
(inches)

Flat 3

2 4

4 5

6 6

For SI units: 1 inch = 25.4 mm
- Vertical measurement from the roof surface at the drain to the highest point of the roof surface served by the drain, ignoring a local depression immediately adjacent to the drain.
1105.2 Setback Roofs. Drains on setback roofs shall be permitted to be connected to the controlled-flow drainage systems provided:

(1) The setback is designed for storing water, or

(2) The square footage of the setback drainage area is converted as outlined in Section 1105.0 to gpm, and the storm-water pipe sizes in the controlled-flow system are based on the sum of the loads.

(3) The branch from each of the roof drains that are not provided with controlled flow shall be sized in accordance

with Table 1103.1.

1106.0 Engineered Storm Drainage System. 1106.1 General. The design and sizing of a storm drainage system shall be permitted to be determined by accepted engineering practices. The system shall be designed by a regis

TABLE 1105.1(1) CONTROLLED-FLOW MAXIMUM ROOF WATER DEPTH

For SI units: 1 inch = 25.4 mm
- Vertical measurement from the roof surface at the drain to the highest point of the roof surface served by the drain, ignoring a local depression immediately adjacent to the drain.
TABLE 1105.1(2) DISTANCE OF SCUPPER BOTTOMS ABOVE ROOF

For SI units: 1 inch = 25.4 mm
CPC § 0.028 Medium relevance — show source text
7
|0.028
| |South Bend|2.7|0.028| |||| |IOWA
|–
|–
| |Council Bluffs
|3.7
|0.038
| |Davenport
|3.0
|0.031
| |Des Moines
|3.4
|0.035
| |Sioux City|3.6|0.037| |||| |KANSAS
|–
|–
| |Goodland
|3.5
|0.036
| |Salina
|3.8
|0.039
| |Topeka
|3.8
|0.039
| |Wichita|3.9|0.041| |||| |KENTUCKY
|–
|–
| |Bowling Green
|2.9
|0.030
| |Lexington
|2.9
|0.030
| |Louisville
|2.8
|0.029
| |Paducah|3.0|0.031| |||| |LOUISIANA
|–
|–
| |Monroe
|3.8
|0.039
| |New Orleans
|4.5
|0.047
| |Shreveport|4.0|0.042| |||| |MAINE
|–
|–
| |Bangor
|2.2
|0.023
| |Kittery
|2.4
|0.025
| |Millinocket|2.0|0.021| |||| |MARYLAND
|–
|–
| |Baltimore
|3.6
|0.037
| |Frostburg
|2.9
|0.030
| |Ocean City|3.7|0.038| |||| |MASSACHUSETTS
|–
|–
| |Adams
|2.6
|0.027
| |Boston
|2.7
|0.028
| |Springfield|2.7|0.028| |||| |MICHIGAN
|–
|–
| |Detroit
|2.5
|0.026
| |Grand Rapids
|2.6
|0.027
| |Kalamazoo|2.7|~~0.028~~|

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APPENDIX D

TABLE D 101.1 MAXIMUM RATES OF RAINFALL FOR VARIOUS CITIES (continued)*

ROOF RISE* (inches)	MAXIMUM WATER DEPTH AT DRAIN (inches)
Flat	3
2	4
4	5
6	6

ROOF RISE* (inches)	ABOVE ROOF LEVEL AT DRAIN (inches)
Flat	3
2	4
4	5
6	6

CPC § 0.06 Medium relevance — show source text

SIZE OF PIPE	FLOW (1⁄2 inch per foot slope)	MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES (square feet)	Col4	Col5	Col6	Col7	Col8
inches	gpm	1 (in/h)	2 (in/h)	3 (in/h)	4 (in/h)	5 (in/h)	6 (in/h)
3	68	6576	3288	2192	1644	1310	1096
4	156	15 040	7520	5010	3760	3010	2500
5	278	26 720	13 360	8900	6680	5320	4450
6	445	42 800	21 400	14 267	10 700	8580	7140
8	956	92 000	46 000	30 650	23 000	18 400	15 320
10	1721	165 600	82 800	55 200	41 400	33 150	27 600
12	2768	266 400	133 200	88 800	66 600	53 200	44 400
15	4946	476 000	238 000	158 700	119 000	95 200	79 300

For SI units: 1 inch = 25 mm, 1 gallon per minute = 0.06 L/s, [1] ⁄ 8 inch per foot = 10.4 mm/m, 1 inch per hour = 25.4 mm/h, 1 square foot = 0.0929 m [2]

Notes: 1 The sizing data for horizontal piping are based on the pipes flowing full. 2 For rainfall rates other than those listed, determine the allowable roof area by dividing the area given in the 1 inch per hour (25.4 mm/h) column by the desired rainfall rate.

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STORM DRAINAGE

CPC § 0.06 Medium relevance — show source text

For SI units: 1 inch = 25 mm, 1 gallon per minute = 0.06 L/s, [1] ⁄ 8 inch per foot = 10.4 mm/m, 1 inch per hour = 25.4 mm/h, 1 square foot = 0.0929 m [2]

210 2025 CALIFORNIA PLUMBING CODE

STORM DRAINAGE

Col1	TABLE 1103.3 SIZE OF GUTTERS	Col3	Col4	Col5	Col6
DIAMETER OF GUTTER (1⁄16inch per foot slope)	MAXIMUM RAINFALL RATES BASED ON ROOF AREA (square feet)	MAXIMUM RAINFALL RATES BASED ON ROOF AREA (square feet)	MAXIMUM RAINFALL RATES BASED ON ROOF AREA (square feet)	MAXIMUM RAINFALL RATES BASED ON ROOF AREA (square feet)	MAXIMUM RAINFALL RATES BASED ON ROOF AREA (square feet)
inches	2 (in/h)	3 (in/h)	4 (in/h)	5 (in/h)	6 (in/h)
3	340	226	170	136	113
4	720	480	360	288	240
5	1250	834	625	500	416
6	1920	1280	960	768	640
7	2760	1840	1380	1100	918
8	3980	2655	1990	1590	1325
10	7200	4800	3600	2880	2400

DIAMETER OF GUTTER (1⁄8 inch per foot slope)	MAXIMUM RAINFALL RATES BASED ON ROOF AREA (square feet)	Col3	Col4	Col5	Col6
inches	2 (in/h)	3 (in/h)	4 (in/h)	5 (in/h)	6 (in/h)
3	480	320	240	192	160
4	1020	681	510	408	340
5	1760	1172	880	704	587
6	2720	1815	1360	1085	905
7	3900	2600	1950	1560	1300
8	5600	3740	2800	2240	1870
10	10 200	6800	5100	4080	3400

CPC § 0.06 Medium relevance — show source text
AT VARIOUS RAINFALL RATES**
(square feet)|MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)| |inches|gpm1|1 (in/h)|2 (in/h)|3 (in/h)|4 (in/h)|5 (in/h)|6 (in/h)|7 (in/h)|8 (in/h)|9 (in/h)|10 (in/h)|11 (in/h)|12 (in/h)| |2|30|2880|1440|960|720|575|480|410|360|320|290|260|240| |3|92|8800|4400|2930|2200|1760|1470|1260|1100|980|880|800|730| |4|192|18 400|9200|6130|4600|3680|3070|2630|2300|2045|1840|1675|1530| |5|360|34 600|17 300|11 530|8650|6920|5765|4945|4325|3845|3460|3145|2880| |6|563|54 000|27 000|17 995|13 500|10 800|9000|7715|6750|6000|5400|4910|4500| |8|1208|116 000|58 000|38 660|29 000|23 200|19 315|16 570|14 500|12 890|11 600|10 545|9600|

For SI units: 1 inch = 25 mm, 1 gallon per minute = 0.06 L/s, 1 inch per hour = 25.4 mm/h, 1 square foot = 0.0929 m [2]

Notes: 1 Maximum discharge capacity, gpm (L/s) with approximately 1 3 ⁄ 4 inch (44 mm) head of water at the drain. 2 For rainfall rates other than those listed, determine the allowable roof area by dividing the area given in the 1 inch per hour (25.4 mm/h) column by the desired rainfall rate. 3 Vertical piping shall be round, square, or rectangular. Square pipe shall be sized to enclose its equivalent round pipe. Rectangular pipe shall have not less than the same cross-sectional area as its equivalent round pipe, except that the ratio of its side dimensions shall not exceed 3 to 1.

(3) For two adjacent walls of unequal height – add 35 percent of the total common height and add 50 percent of the remaining height of the highest wall. (4) Two opposite walls of same height – add no additional

area.
CPC § 0.06 Medium relevance — show source text
600|17 300|11 530|8650|6920|5765|4945|4325|3845|3460|3145|2880| |6|563|54 000|27 000|17 995|13 500|10 800|9000|7715|6750|6000|5400|4910|4500| |8|1208|116 000|58 000|38 660|29 000|23 200|19 315|16 570|14 500|12 890|11 600|10 545|9600|

For SI units: 1 inch = 25 mm, 1 gallon per minute = 0.06 L/s, 1 inch per hour = 25.4 mm/h, 1 square foot = 0.0929 m [2]

Notes: 1 Maximum discharge capacity, gpm (L/s) with approximately 1 3 ⁄ 4 inch (44 mm) head of water at the drain. 2 For rainfall rates other than those listed, determine the allowable roof area by dividing the area given in the 1 inch per hour (25.4 mm/h) column by the desired rainfall rate. 3 Vertical piping shall be round, square, or rectangular. Square pipe shall be sized to enclose its equivalent round pipe. Rectangular pipe shall have not less than the same cross-sectional area as its equivalent round pipe, except that the ratio of its side dimensions shall not exceed 3 to 1.

(3) For two adjacent walls of unequal height – add 35 percent of the total common height and add 50 percent of the remaining height of the highest wall. (4) Two opposite walls of same height – add no additional

area.

(5) Two opposite walls of differing heights – add 50 percent of the wall area above the top of the lower wall. (6) Walls on three sides – add 50 percent of the area of the inner wall below the top of the lowest wall, plus an allowance for the area of the wall above the top of the lowest wall, in accordance with Section 1103.4(3) and Section 1103.4(5) above. (7) Walls on four sides – no allowance for wall areas below the top of the lowest wall – add for areas above the top of the lowest wall in accordance with Section 1103.4(1), Section 1103.4(3), Section 1103.4(5), and Section 1103.4(6) above.

1104.0 Values for Continuous Flow.

1104.1 General. Where there is a continuous or semi-continuous discharge into the building storm drain or building storm sewer, as from a pump, ejector, air-conditioning plant, or similar device, 1 gpm (0.06 L/s) of such discharge shall be computed as being equivalent to 24 square feet (2.2 m [2] ) of roof area, based upon a rate of rainfall of 4 inches per hour (in/h) (102 mm/h).

1105.0 Controlled-Flow Roof Drainage. 1105.1 Application. Instead of sizing the storm drainage system in accordance with Section 1103.0, the roof drainage shall be permitted to be sized by controlled flow and storage of the storm water on the roof, provided the following conditions are met:

(1) The water from a 25-year frequency storm shall not be stored on the roof exceeding 24 hours.

California Plumbing Code Medium relevance — show source text

200|66 600|44 400|33 300|26 650|22 200| |15|2473|238 000|119 000|79 333|59 500|47 600|39 650|

SIZE OF PIPE	FLOW (1⁄4 inch per foot slope)	MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES (square feet)	Col4	Col5	Col6	Col7	Col8
inches	gpm	1 (in/h)	2 (in/h)	3 (in/h)	4 (in/h)	5 (in/h)	6 (in/h)
3	48	4640	2320	1546	1160	928	773
4	110	10 600	5300	3533	2650	2120	1766
5	196	18 880	9440	6293	4720	3776	3146
6	314	30 200	15 100	10 066	7550	6040	5033
8	677	65 200	32 600	21 733	16 300	13 040	10 866
10	1214	116 800	58 400	38 950	29 200	23 350	19 450
12	1953	188 000	94 000	62 600	47 000	37 600	31 350
15	3491	336 000	168 000	112 000	84 000	67 250	56 000

SIZE OF PIPE	FLOW (1⁄2 inch per foot slope)	MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES (square feet)	Col4	Col5	Col6	Col7	Col8
inches	gpm	1 (in/h)	2 (in/h)	3 (in/h)	4 (in/h)	5 (in/h)	6 (in/h)
3	68	6576	3288	2192	1644	1310	1096
4	156	15 040	7520	5010	3760	3010	2500
5	278	26 720	13 360	8900	6680	5320	4450
6	445	42 800	21 400	14 267	10 700	8580	7140
8	956	92 000	46 000	30 650	23 000	18 400	15 320
10	1721	165 600	82 800	55 200	41 400	33 150	27 600
12	2768	266 400	133 200	88 800	66 600	53 200	44 400
15	4946	476 000	238 000	158 700	119 000	95 200	79 300

California Plumbing Code Medium relevance — show source text
OF PIPE**|FLOW
(1⁄8 inch per foot
slope)|MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)|MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)|MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)|MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)|MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)|MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)| |inches|gpm|1 (in/h)|2 (in/h)|3 (in/h)|4 (in/h)|5 (in/h)|6 (in/h)| |3|34|3288|1644|1096|822|657|548| |4|78|7520|3760|2506|1880|1504|1253| |5|139|13 360|6680|4453|3340|2672|2227| |6|222|21 400|10 700|7133|5350|4280|3566| |8|478|46 000|23 000|15 330|11 500|9200|7670| |10|860|82 800|41 400|27 600|20 700|16 580|13 800| |12|1384|133 200|66 600|44 400|33 300|26 650|22 200| |15|2473|238 000|119 000|79 333|59 500|47 600|39 650|

California Plumbing Code Medium relevance — show source text

RATES**
(square feet)|MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)|MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)|MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)|MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)| |inches|gpm|1 (in/h)|2 (in/h)|3 (in/h)|4 (in/h)|5 (in/h)|6 (in/h)| |3|34|3288|1644|1096|822|657|548| |4|78|7520|3760|2506|1880|1504|1253| |5|139|13 360|6680|4453|3340|2672|2227| |6|222|21 400|10 700|7133|5350|4280|3566| |8|478|46 000|23 000|15 330|11 500|9200|7670| |10|860|82 800|41 400|27 600|20 700|16 580|13 800| |12|1384|133 200|66 600|44 400|33 300|26 650|22 200| |15|2473|238 000|119 000|79 333|59 500|47 600|39 650|

SIZE OF PIPE	FLOW (1⁄4 inch per foot slope)	MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES (square feet)	Col4	Col5	Col6	Col7	Col8
inches	gpm	1 (in/h)	2 (in/h)	3 (in/h)	4 (in/h)	5 (in/h)	6 (in/h)
3	48	4640	2320	1546	1160	928	773
4	110	10 600	5300	3533	2650	2120	1766
5	196	18 880	9440	6293	4720	3776	3146
6	314	30 200	15 100	10 066	7550	6040	5033
8	677	65 200	32 600	21 733	16 300	13 040	10 866
10	1214	116 800	58 400	38 950	29 200	23 350	19 450
12	1953	188 000	94 000	62 600	47 000	37 600	31 350
15	3491	336 000	168 000	112 000	84 000	67 250	56 000

CPC § 3.9 Medium relevance — show source text

Smith
|3.9
|0.041
| |Jonesboro
|3.5
|0.036
| |Little Rock|3.7|~~0.038~~|

2025 CALIFORNIA PLUMBING CODE 397

APPENDIX D

TABLE D 101.1 MAXIMUM RATES OF RAINFALL FOR VARIOUS CITIES (continued)*

STATES AND CITIES	STORM DRAINAGE 60-MINUTE DURATION, 100-YEAR RETURN	Col3
STATES AND CITIES	inches per hour	gallons per minute per square foot
CALIFORNIA	–	–
Eureka	1.5	0.016
Lake Tahoe	1.3	0.014
Los Angeles	2.0	0.021
Lucerne Valley	2.5	0.026
Needles	1.5	0.016
Palmdale	3.0	0.031
Redding	1.5	0.016
San Diego	1.5	0.016
San Francisco	1.5	0.016
San Luis Obispo	1.5	0.016

COLORADO	–	–
Craig	1.5	0.016
Denver	2.2	0.023
Durango	1.8	0.019
Stratton	3.0	0.031

CONNECTICUT	–	–
Hartford	2.8	0.029
New Haven	3.0	0.031

DELAWARE	–	–
Dover	3.5	0.036
Rehobeth Beach	3.6	0.037

DISTRICT OF COLUMBIA	–	–
Washington	4.0	0.042

FLORIDA	–	–
Daytona Beach	4.0	0.042
Ft.

CPC § 0-60 Medium relevance — show source text
e
(Installations on spaced/solid sheathing with battens or spaced sheathing)**| |Maximum Allow-
able Stress Design
Wind Speed,****Vasd
f
(mph)|Mean roof
height (feet)|Roof slope < 5:12|Roof slope 5:12 < 12:12|Roof slope 12:12 and over| |85|0-60|Fasteners are not required.
Tiles with installed weight less
than 9 lbs./sq. ft. require not
fewer than one fastener per tile.|One fastener per tile every other
row. Perimeter tiles require one
fastener. Tiles with installed weight
less than 9 lbs./sq. ft. require not
fewer than one fastener per tile.|One fastener required for
every tile. Tiles with
installed weight less than 9
lbs./sq. ft. require not fewer
than one fastener per tile.| |100|0-40|0-40|0-40|0-40| |100|> 40-60|The head of all tiles shall be nailed. The nose of all eave tiles shall be fastened with approved clips.
Rake5 tiles shall be nailed with two nails. The nose of all ridge, hip and rake tiles shall be set in a bead
of roofer’s mastic.|The head of all tiles shall be nailed. The nose of all eave tiles shall be fastened with approved clips.
Rake5 tiles shall be nailed with two nails. The nose of all ridge, hip and rake tiles shall be set in a bead
of roofer’s mastic.|The head of all tiles shall be nailed. The nose of all eave tiles shall be fastened with approved clips.
Rake5 tiles shall be nailed with two nails. The nose of all ridge, hip and rake tiles shall be set in a bead
of roofer’s mastic.| |110|0-60|The fastening system shall resist the wind forces in Section 1609.6.3.1.|The fastening system shall resist the wind forces in Section 1609.6.3.1.|The fastening system shall resist the wind forces in Section 1609.6.3.1.| |120|0-60|The fastening system shall resist the wind forces in Section 1609.6.3.1.|The fastening system shall resist the wind forces in Section 1609.6.3.1.|The fastening system shall resist the wind forces in Section 1609.6.3.1.| |130|0-60|The fastening system shall resist the wind forces in Section 1609.6.3.1.|The fastening system shall resist the wind forces in Section 1609.6.3.1.|The fastening system shall resist the wind forces in Section 1609.6.3.1.| |All|> 60|The fastening system shall resist the wind forces in Section 1609.6.3.1.|The fastening system shall resist the wind forces in Section 1609.6.3.1.|The fastening system shall resist the wind forces in Section 1609.6.3.1.
CPC § 0.004 Medium relevance — show source text
35|0.004|–|–| |0.71
|0.013
|0.003
|–
| |1.06
|0.025
|0.005
|–
| |1.41
|0.041
|0.008
|–
| |1.77
|0.060
|0.012
|–
| |2.12
|0.082
|0.016
|–
| |2.47
|0.107
|0.021
|–
| |2.82
|0.135
|0.026
|–
| |3.18|0.166|0.032|–| |3.53|0.199|0.038|–| |4.24|0.274|0.053|–| |4.94|0.359|0.069|–| |5.65|0.454|0.087|–| |6.36|0.558|0.107|–| |7.06|0.672|0.129|0.033| |7.77|0.795|0.153|0.039| |8.47|0.927|0.179|0.045| |9.18|1.066|0.205|0.052| |9.89|1.218|0.233|0.059| |10.59|1.377|0.263|0.066| |12.36|1.811|0.346|0.087| |14.12|2.298|0.438|0.110| |15.89|2.837|0.539|0.135| |17.66|3.456|0.650|0.163| |19.42|–|0.771|0.193| |21.19|–|0.900|0.225| |22.95|–|1.038|0.260| |24.72|–|1.185|0.295| |28.25|–|1.505|0.375| |31.78|–|1.859|0.463| |35.31|–|2.247|0.559| |38.84|–|2.667|0.663| |42.37|–|3.121|0.775| |45.90|–|3.607|0.895| |49.43|–|4.125|1.022| |52.97|–|–|1.157| |56.50|–|–|1.299| |60.03|–|–|1.449| |63.56|–|–|1.607| |67.09|–|–|1.772| |70.62|–|–|1.944| |81.21|–|–|2.503| |91.81|–|–|3.127| |102.40|–|–|3.813|

For SI units: 1 standard cubic foot per minute = 28.32 SLPM, 1 inch = 25 mm, 1 foot = 304.8 mm, 1 pound-force per square inch = 6.8947 kPa
CPC § 8.8 Medium relevance — show source text
**
HOURS| |ITEM CODE|DEPTH|CONSTRUCTION DETAILS|LOAD|TIME|PRE-BMS-92|BMS-92|POST-BMS-92|POST-BMS-92|POST-BMS-92| |B-11-RC-1|11″|24″ wide × 11″ deep reinforced concrete “T”
beam (3290 psi); details: see Note 5 figure.|8.8 tons|4 hrs
2 min|||7|1, 2, 14|4| |B-10-RC-2|10″|24″ wide × 10″ deep reinforced concrete “T”
beam (4370 psi); details: see Note 6 figure.|8.8 tons|1 hr
53
min|||7|1, 3|13/4| |B-10-RC-3|101/2″|24″ wide × 101/2″ deep reinforced concrete
“T” beam (4450 psi); details: see Note 7
figure.|8.8 tons|2 hrs
40
min|||7|1, 3|22/3| |B-11-RC-4|11″|24″ wide × 11″ deep reinforced concrete “T”
beam (2400 psi); details: see Note 8 figure.|8.8 tons|3 hrs
32
min|||7|1, 3, 14|31/2| |B-11-RC-5|11″|24″ wide × 11″ deep reinforced concrete “T”
beam (4250 psi); details: see Note 9 figure.|8.8 tons|3 hrs
3 min|||7|1, 3, 14|3| |B-11-RC-6|11″|Concrete flange: 4″ deep × 2' wide (4895 psi)
concrete; concrete beam: 7″ deep × 61/2″
wide; “I” beam reinforcement; 10″ × 41/2″ ×
25 lbs R.S.J.; 1″ cover on flanges; flange rein-
forcement:3/8″ diameter bars at 6″ pitch
parallel to “T”; 1/4″ diameter bars perpendic-
ular to “T”; beam reinforcement: 4″ × 6″ No.
13 SWG wire mesh; span: 11' restrained;
details: see Note 10 figure.|10 tons|6 hrs|||7|1, 4|6| |B-11-RC-7|11″|Concrete flange: 6″ deep × 1' 61/2″ wide (3525
psi) concrete; concrete beam: 5″ deep × 8″
wide precast concrete blocks 83/4″ long; “I”
beam reinforcement; 7″ × 4″ × 16 lbs R.S.J.

Frequently asked questions

When does Appendix D NOT apply?

Appendix D provisions are not mandatory unless your state agency or local jurisdiction adopts them; always confirm with the Authority Having Jurisdiction before relying on Appendix D for code compliance (§ D101.1) .

If I use an engineered design, do I still follow Appendix D?

No. An engineered design follows accepted engineering practice and the engineer’s calculations; Appendix D is an alternate, table‑based method used only when the AHJ permits or when the designer chooses it for a non‑adopted, advisory sizing — and engineered designs must be prepared and stamped by a registered design professional (§ 1106.1) .

Where do I get the rainfall value for my city?

Use the gpm per ft² value in Table D 101.1 for your city (or a higher locally established value) when using the Appendix D flow‑rate method (§ D102.1) file.

Do siphonic drains require anything special?

Yes — siphonic roof drainage systems must be designed to ASPE/ANSI 45 and siphonic drains must comply with ASME A112.6.9 (see § 1106.2 and § 1106.3) .

What tables do I use to convert required gpm into pipe sizes?

Use Table 1103.1 and Table 1103.2 (Chapter 11). Appendix D references those tables for required pipe sizes after you compute flow or allowable roof area (§ D102.1) file.

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