CPC · California Plumbing Code

What standards and code rules apply to siphonic roof drainage systems and drains?

Q: Who must stamp the siphonic roof drainage calculations?

A registered design professional must prepare and stamp the engineered design per § 1106.1 .

Q: Does the CPC give the hydraulic equations for siphonic systems?

No. The CPC requires compliance with ASPE/ANSI 45 for siphonic systems ( § 1106.2 ); the detailed hydraulic methods are in that standard, not verbatim in the CPC.

Q: Can I use a drain not certified to ASME A112.6.9?

No. § 1106.3 requires siphonic roof drains to comply with ASME A112.6.9 ; using noncompliant drains would not meet that Code requirement without AHJ-approved equivalency.

Q: Where in the Code does it list ASPE/ANSI 45 and ASME A112.6.9?

Those standards are referenced in § 1106.2 and § 1106.3 respectively, and appear in the CPC’s referenced-standards tables (Chapter 17).

If you plan to use a siphonic roof drainage system in California, the California Plumbing Code requires that a registered design professional engineer the system (§ 1106.1) and that the design follow **ASPE/ANSI 45** (§ 1106.2) while the actual siphonic drain products meet **ASME A112.6.9** (§ 1106.3). The CPC defers the detailed hydraulic rules to those named standards and still requires testing and AHJ approval under Chapter 11.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

The California Plumbing Code requires that the design and sizing of any engineered storm drainage system be performed by a registered design professional using accepted engineering practice (§ 1106.1) . For siphonic roof drainage systems, the CPC mandates compliance with ASPE/ANSI 45 (§ 1106.2) and that the siphonic roof drains themselves comply with ASME A112.6.9 (§ 1106.3) . The CPC references these standards as the required technical documents for siphonic design and product conformity (see Chapter 17 referenced-standards tables) .

The single most important rule: any siphonic roof drainage system in California must be engineered and approved by a registered design professional and built to the specific external standards the Code names — ASPE/ANSI 45 for system design and ASME A112.6.9 for the drains — because the CPC does not provide the detailed siphonic calculations itself.

Requirements in detail

Who must design and approve?

The design and sizing of an engineered storm drainage system is permitted to be based on accepted engineering practice but must be designed by a registered design professional and approved per § 1106.1.

Which standards are mandatory?

System design: comply with ASPE/ANSI 45 as required by § 1106.2.
Drain product: all siphonic roof drains must comply with ASME A112.6.9 per § 1106.3.

Note: The CPC refers to these standards in its referenced-standards tables; the Code defers the technical details (hydraulic procedure, testing, physical dimensions, installation details) to those standards rather than reproducing them in Chapter 11 .

Testing and inspection linkage

Storm drainage systems (including new and altered systems) are subject to the CPC testing rules in Chapter 11 (see § 1107.1 and following); the Code requires testing to disclose leaks/defects and prescribes water or air test methods for storm drainage piping. Use those testing rules in concert with the engineered siphonic design.

Quick reference table (decision-relevant values)

Decision item	Required value / actor	Code Reference
Who designs the system	Registered design professional (engineer or architect as applicable)	§ 1106.1
Design standard for siphonic systems	ASPE/ANSI 45 (siphonic roof drainage)	§ 1106.2
Product standard for siphonic drains	ASME A112.6.9 (siphonic roof drains)	§ 1106.3
Approval by AHJ	System must be approved in accordance with Section 301.5 (plan review/approval)	§ 1106.1
Testing of new/altered systems	Water or air testing per § 1107.1–1107.2	§ 1107.1
Where to find technical parameters	Refer to the referenced standards (Chapter 17 lists ASPE/ANSI 45 and ASME A112.6.9)	Table 1701.1 / Chapter 17

Exceptions & special cases

The texts of § 1106.1–1106.3 do not themselves list exceptions to the requirement to follow the named standards; they require the registered design professional and the named standards for siphonic systems and drains. If an Authority Having Jurisdiction (AHJ) allows an alternative, that is handled through the permit/approval pathway (see Section 301.5) — the CPC text for 1106 does not enumerate alternative methods or exceptions in those specific subsections .
The CPC does not reproduce the technical content of ASPE/ANSI 45 or ASME A112.6.9; any project-specific exceptions or equivalencies to those standards would need separate justification and AHJ approval (and the Code’s referenced standards table shows these standards are the mandatory technical references) .

Common mistakes

Assuming CPC contains the detailed siphonic hydraulic procedures. It does not — ASPE/ANSI 45 contains the design methodology; the CPC simply mandates compliance with it under § 1106.2 .
Installing siphonic roof drains that are not certified to ASME A112.6.9. The CPC requires conformity to that standard in § 1106.3 .
Skipping professional design. Because § 1106.1 requires a registered design professional for engineered systems, submitting “rule-of-thumb” or table-only sizing for a siphonic system is not compliant.
Forgetting testing. New or altered storm drainage systems must be tested per § 1107; siphonic systems are not exempt from the CPC testing provisions.

Worked example — applying the rule (process, not numeric design details)

Scenario: You are the design team for a 20,000 ft² flat commercial roof and want to use a siphonic roof-drainage system.

Steps required by the CPC:

Engage a registered design professional to perform the design and sizing (required by § 1106.1) .
Require the engineer to design the siphonic system in strict accordance with ASPE/ANSI 45 (the CPC-required design standard, § 1106.2) — obtain or reference the ASPE/ANSI 45 procedures for inlet geometry, hydraulic calculations, pipe layouts, air-admittance considerations, surge analysis, and required testing protocols. The CPC does not supply these calculation methods; they exist in ASPE/ANSI 45.
Specify siphonic roof drains listed or certified to ASME A112.6.9 in the construction documents (per § 1106.3) and include manufacturer certification or product data demonstrating compliance.
Submit the engineered calculations and product data to the AHJ for plan approval per Section 301.5 as required by § 1106.1.
After installation, have the system tested per the CPC’s storm-drain testing provisions (Chapter 11, § 1107), and provide test results to the AHJ as part of final acceptance. The CPC allows water or air testing methods for storm drainage (note limitations for plastic pipe).

Note: This worked example describes procedure and regulatory checkpoints. The actual hydraulic sizing numbers (pipe diameters, inlet capacities, required vacuum conditions) are derived from ASPE/ANSI 45 and the product standard ASME A112.6.9, which must be consulted for the detailed calculations and product requirements — those documents are not reproduced in the CPC text excerpts here .

Related provisions (CPC sections you’ll almost always review with 1106)

§ 1106.1 — Engineered storm drainage design and AHJ approval (design professional)
§ 1106.2 — Siphonic roof drainage systems must comply with ASPE/ANSI 45
§ 1106.3 — Siphonic roof drains must comply with ASME A112.6.9
§ 1107.1–1107.2 — Testing requirements and methods for storm drainage systems (water/air tests)
§ 1101.12.1 / 1101.12.2 — Primary and secondary roof drainage requirements (emergency overflow / scuppers) — coordinate siphonic design with these requirements for overflow protection and secondary drainage where applicable
Chapter 17 / Table 1701.1 — referenced standards listing for ASPE/ANSI 45 and ASME A112.6.9 (shows these standards are the Code’s referenced technical documents)

If you need a checklist or permit-submittal list tailored to your project (what to include from the engineer, product data, test reports), I can prepare one keyed to these CPC sections and typical AHJ review expectations.

Code references

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

CPC § 25.4 High relevance — show source text
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
- 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.
tered design professional and approved in accordance with Section 301.5.

1106.2 Siphonic Roof Drainage Systems. The design of a siphonic roof drainage system shall comply with ASPE/ANSI 45.

1106.3 Siphonic Roof Drains. Siphonic roof drains shall comply with ASME A112.6.9.

1107.0 Testing. 1107.1 Testing Required. New building storm drainage systems and parts of existing systems that have been altered, extended, or repaired shall be tested in accordance with Section 1107.2.1 or Section 1107.2.2 to disclose leaks and

defects.

1107.2 Methods of Testing Storm Drainage Systems. Except for outside leaders and perforated or open-jointed drain tile, the piping of storm drain systems shall be tested upon completion of the rough piping installation by water or air, except that plastic pipe shall not be tested with air, and proved tight. The Authority Having Jurisdiction shall be permitted to require the removal of cleanout plugs to ascertain whether the pressure has reached parts of the system. One of the following test methods shall be used in accordance with Section 1107.2.1 through Section 1107.2.3. 1107.2.1 Water Test. After piping has been installed, the water test shall be applied to the drainage system, either to the entire system or sections. Where the test is applied to the entire system, all openings in the piping shall be tightly closed except for the highest opening, and the system shall be filled with water to the point of overflow.
CPC § 301.5. High relevance — show source text
tered design professional and approved in accordance with Section 301.5.

1106.2 Siphonic Roof Drainage Systems. The design of a siphonic roof drainage system shall comply with ASPE/ANSI 45.

1106.3 Siphonic Roof Drains. Siphonic roof drains shall comply with ASME A112.6.9.

1107.0 Testing. 1107.1 Testing Required. New building storm drainage systems and parts of existing systems that have been altered, extended, or repaired shall be tested in accordance with Section 1107.2.1 or Section 1107.2.2 to disclose leaks and

defects.

1107.2 Methods of Testing Storm Drainage Systems. Except for outside leaders and perforated or open-jointed drain tile, the piping of storm drain systems shall be tested upon completion of the rough piping installation by water or air, except that plastic pipe shall not be tested with air, and proved tight. The Authority Having Jurisdiction shall be permitted to require the removal of cleanout plugs to ascertain whether the pressure has reached parts of the system. One of the following test methods shall be used in accordance with Section 1107.2.1 through Section 1107.2.3. 1107.2.1 Water Test. After piping has been installed, the water test shall be applied to the drainage system, either to the entire system or sections. Where the test is applied to the entire system, all openings in the piping shall be tightly closed except for the highest opening, and the system shall be filled with water to the point of overflow. Where the system is tested in sections, each opening shall be tightly plugged except for the highest opening of the section under test, and each section shall be filled with water, but no section shall be tested with less than a 10 foot (3048 mm) head of water. In testing successive sections, not less than the upper 10 feet (3048 mm) of the next preceding section shall be tested so that no joint of pipe in the building except the uppermost 10 feet (3048 mm) of a roof drainage system, which shall be filled with water to the flood level of the uppermost roof drain, shall have been submitted to a test of less than 10 foot (3048 mm) head of water. The water shall be kept in the system or the portion of the test for not less than 15 minutes before inspection starts; the system shall then be tight. 1107.2.2 Air Test. The air test shall be made by attaching an air compressor testing apparatus to a suitable opening after closing other inlets and outlets to the system, forcing air into the system until there is a uniform gauge pressure of 5 pounds-force per square inch (psi) (34 kPa) or sufficient pressure to balance a column of mercury 10 inches (34 kPa) in height. This pressure shall be held without the introduction of additional air for not

less than 15 minutes.

1107.2.3 Exceptions. Where circumstances exist that make air and water tests described in Section 1107.2.1 and Section 1107.2.2 impractical, see Section 105.3.

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|Col1|Col2|TABLE 1103.
CPC § 1101.16 High 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 § 3-2020 High relevance — show source text

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REFERENCED STANDARDS

TABLE 1701.1 (continued) REFERENCED STANDARDS

STANDARD NUMBER	STANDARD TITLE	APPLICATION	REFERENCED SECTION
ASSE 1012-2009	Backflow Preventers with an Intermediate Atmospheric Vent	Backflow Protection	Table 603.2
ASSE 1013-2021	Reduced Pressure Principle Backflow Prevention Assemblies	Backflow Protection	Table 603.2
ASSE 1014-2020	Backflow Prevention Devices for Hand-Held Showers	Backflow Protection	417.3
ASSE 1015-2021	Double Check Backflow Prevention	Backflow Protection	Table 603.2
ASSE 1016-2017/ASME A112.1016-2017/CSA B125.

CPC § 1103.1 High relevance — show source text
(3) Not less than two drains shall be installed in roof areas of 10 000 square feet (929 m [2] ) or less, and not less than one additional drain shall be installed for each 10 000 square feet (929 m [2] ) of roof area exceeding 10 000 square feet (929 m [2] ). (4) Each roof drain shall have a precalibrated, fixed (nonadjustable), and proportional weir (notched) in a standing water collar inside the strainer. No mechanical devices or valves shall be permitted. (5) Pipe sizing shall be based on the pre-calibrated rate of flow (gpm) (L/s) of the pre-calibrated weir for the maximum allowable water depth, and Table 1103.1 and Table 1103.2.

(6) The height of stones or other granular material above the waterproofed surface shall not be considered in water depth measurement, and the roof surface in the vicinity of the drain shall not be recessed to create a reservoir.

(7) Roof design, where controlled-flow roof drainage is used, shall be such that the design roof live load is not less than 30 lb/ft [2] (146 kg/m [2] ) to provide a safety factor exceeding the 15 lb/ft [2] (73 kg/m [2] ) represented by the depth of water stored on the roof in accordance with Table 1105.1(1). (8) Scuppers shall be provided in parapet walls. The distance of scupper bottoms above the roof level at the drains shall not exceed the maximum distances specified in Table 1105.1(2).

(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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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
CPC § 1105.1 High relevance — show source text
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

CHAPTER 12 FUEL GAS PIPING . . . . . . . . . . .213

1201.0 General . . . . . . . . . . . . . . . . . . . . .215

1201.1 Applicability . . . . . . . . . . . . . . . . . .215

1202.0 Coverage of Piping System . . . . .215

1202.1 General . . . . . . . . . . . . . . . . . . . . .215

1202.2 Piping System Requirements . . . .215

1202.3 Applications . . . . . . . . . . . . . . . . .215

1203.0 Inspection . . . . . . . . . . . . . . . . . . .215

1203.1 Inspection Notification . . . . . . . . .215

1203.2 Excavation . . . . . . . . . . . . . . . . . .215

1203.3 Type of Inspections . . . . . . . . . . .215

1203.4 Inspection Waived . . . . . . . . . . . .216

1204.0 Certificate of Inspection . . . . . . . .216

1204.1 Issuance . . . . . . . . . . . . . . . . . . . .216

1204.2 Gas Supplier . . . . . . . . . . . . . . . . .216

1204.3 Unlawful . . . . . . . . . . . . . . . . . . . .216

1205.0 Authority to Render Gas Service . . . . . . . . . . . . . . . . . . . . .216

1205.1 Authorized Personnel . . . . . . . . . .216
CPC § 1101.11 High relevance — show source text
1101.11 Paved Areas. Where the occupant creates surface water drainage, the sumps, gratings, or floor drains shall be piped to a storm drain or an approved water course. 1101.12 Roof Drainage. Roof drainage shall comply with Section 1101.12.1 and Section 1101.12.2.

1101.12.1 Primary Roof Drainage. Roof areas of a building shall be drained by roof drains or gutters. The location and sizing of drains and gutters shall be coordinated with the structural design and pitch of the roof. Unless otherwise required by the Authority Having Jurisdiction, roof drains, gutters, vertical conductors or leaders, and horizontal storm drains for primary drainage shall be sized based on a storm of 60 minutes duration and 100 year return period. Refer to Table D 101.1 (in Appendix D) for 100 years, 60-minute storms at various locations. 1101.12.2 Secondary Drainage. Secondary (emergency) roof drainage shall be provided by one of the methods specified in Section 1101.12.2.1 or Section 1101.12.2.2.

1101.12.2.1 Roof Scuppers or Open Side. Secondary roof drainage shall be provided by an opensided roof or scuppers where the roof perimeter construction extends above the roof in such a manner that water will be entrapped. An open-sided roof or scuppers shall be sized to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by Section 1101.12.1. Scupper openings shall be not less than 4 inches (102 mm) high and have a width equal to the circumference of the roof drain required for the area served, sized in accordance with Table 1103.1.

1101.12.2.2 Secondary Roof Drain. Secondary roof drains shall be provided. The secondary roof drains shall be located not less than 2 inches (51 mm) above the roof surface. The maximum height of the roof drains shall be a height to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by Section 1101.12.1. The secondary roof drains shall connect to a piping system in accordance with Section 1101.12.2.2.1 or Section 1101.12.2.2.2.

1101.12.2.2.1 Separate Piping System. The secondary roof drainage system shall be a

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separate system of piping, independent of the primary roof drainage system. The discharge shall be above grade, in a location observable by the building occupants or maintenance personnel. Secondary roof drain systems shall be sized in accordance with Section 1101.12.1

based on the rainfall rate for which the primary system is sized. 1101.12.2.2.2 Combined System. The secondary roof drains shall connect to the vertical piping of the primary storm drainage conductor downstream of the last horizontal offset located below the roof. The primary storm drainage system shall connect to the building storm water that connects to an underground public storm sewer. The combined secondary and primary roof drain systems shall be sized in accordance with Section 1103.0 based on double the rain fall rate for the local area.
CPC § 1103.1. High 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 § 1501.1 High relevance — show source text
ICC code development note: Code change proposals to sections preceded by the designation [BF] or [P] will be considered by one of the code development committees meeting during the 2024 (Group A) Code Development Cycle. All other code change proposals will be considered by a code development committee meeting during the 2025 (Group B) Code Development Cycle.

SECTION 1501—GENERAL

1501.1 Scope. The provisions of this chapter shall govern the design, materials, construction and quality of roof assemblies, and rooftop structures.

SECTION 1502—ROOF DRAINAGE

[P] 1502.1 General. Design and installation of roof drainage systems shall comply with this section, Section 1611 of this code and Chapter 11 of the California Plumbing Code .

[P] 1502.2 Secondary (emergency overflow) drains or scuppers. Where roof drains are required, secondary (emergency overflow) roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in such a manner that water will be entrapped if the primary drains allow buildup for any reason. The installation and sizing of secondary emergency overflow drains, leaders and conductors shall comply with Section 1611 of this code and Chapter 11 of the California Plumbing Code .

1502.3 Gutters. Gutters and leaders placed on the outside of buildings, other than Group R-3, private garages and buildings of Type V construction, shall be of noncombustible material or not less than Schedule 40 plastic pipe.

SECTION 1503—WEATHER PROTECTION

1503.1 General. Roof decks shall be covered with approved roof coverings secured to the building or structure in accordance with the provisions of this chapter. Roof coverings shall be designed in accordance with this code, and installed in accordance with this code and the manufacturer’s approved instructions.

1503.2 Flashing. Flashing shall be installed in such a manner so as to prevent water from entering the wall and roof through joints in copings, through moisture-permeable materials and at intersections with parapet walls and other penetrations through the roof plane.

1503.2.1 Locations. Flashing shall be installed at wall and roof intersections, at gutters, wherever there is a change in roof slope or direction and around roof openings. Where flashing is of metal, the metal shall be corrosion resistant with a thickness of not less than 0.019 inch (0.483 mm) (No. 26 galvanized sheet).

1503.3 Parapet walls. Parapet walls shall be coped or covered in accordance with Sections 1503.3.1 and 1503.3.2. The top surface of the parapet wall shall provide positive drainage.

1503.3.1 Fire-resistance-rated parapet walls. Parapet walls required by Section 705.12 shall be coped or covered with weatherproof materials of a width not less than the thickness of the parapet wall such that the fire-resistance rating of the wall is not decreased.

1503.3.2 Other parapet walls. Parapet walls meeting one of the exceptions in Section 705.12 shall be coped or covered with weatherproof materials of a width not less than the thickness of the parapet wall.

1503.4 Attic and rafter ventilation. Intake and exhaust vents for ventilation of attic and enclosed rafter assemblies shall be provided in accordance with Section 1202.2 and the vent product manufacturer’s installation instructions.

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

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 § 4.2 High relevance — show source text

2025 CALIFORNIA PLUMBING CODE 335

REFERENCED STANDARDS

TABLE 1701.1 (continued) REFERENCED STANDARDS

STANDARD NUMBER	STANDARD TITLE	APPLICATION	REFERENCED SECTION
ASME A112.14.6-2010 (R2019)	FOG (Fats, Oils, and Greases) Disposal Systems	Fixtures	1015.2, Table 1009.1
ASME A112.18.1- 2018/CSA B125.1-2018	Plumbing Supply Fittings	Fittings	408.4, 417.1, 417.2, 417.3, 417.4, 417.6, 603.5.20
ASME A112.18.2- 2020/CSA B125.2-2020	Plumbing Waste Fittings	Fittings	404.1, 408.5
ASME A112.18.3-2002 (R2017)	Backflow Protection Devices and Systems in Plumbing Fixture Fittings	Backflow Protection	417.3, 417.4
ASME A112.18.6-2017/ CSA B125.

CPC § 1101.12.2.2 High relevance — show source text
1101.12.2.2 Secondary Roof Drain. Secondary roof drains shall be provided. The secondary roof drains shall be located not less than 2 inches (51 mm) above the roof surface. The maximum height of the roof drains shall be a height to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by Section 1101.12.1. The secondary roof drains shall connect to a piping system in accordance with Section 1101.12.2.2.1 or Section 1101.12.2.2.2.

1101.12.2.2.1 Separate Piping System. The secondary roof drainage system shall be a

206 2025 CALIFORNIA PLUMBING CODE

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

STORM DRAINAGE

separate system of piping, independent of the primary roof drainage system. The discharge shall be above grade, in a location observable by the building occupants or maintenance personnel. Secondary roof drain systems shall be sized in accordance with Section 1101.12.1

based on the rainfall rate for which the primary system is sized. 1101.12.2.2.2 Combined System. The secondary roof drains shall connect to the vertical piping of the primary storm drainage conductor downstream of the last horizontal offset located below the roof. The primary storm drainage system shall connect to the building storm water that connects to an underground public storm sewer. The combined secondary and primary roof drain systems shall be sized in accordance with Section 1103.0 based on double the rain fall rate for the local area.

1101.13 Cleanouts. Cleanouts for building storm drains shall comply with the requirements of Section 719.0 of this code.

1101.13.1 Rain Leaders and Conductors. Rain leaders and conductors connected to a building storm sewer shall have a cleanout installed at the base of the

leader or conductor before it connects to the horizontal

drain.

1101.14 Rainwater Sumps. Rainwater sumps serving “public use” occupancy buildings shall be provided with dual pumps arranged to function alternately in the case of overload or mechanical failure. Pumps rated 600 V or less shall comply with UL 778 and shall be installed in accordance with the manufacturer’s installation instructions.

1101.15 Traps on Storm Drains and Leaders. Leaders and storm drains, where connected to a combined sewer, shall be trapped. Floor and area drains connected to a storm drain shall be trapped.

Exception: Traps shall not be required where roof drains, rain leaders, and other inlets are at locations permitted under Section 906.0, Vent Termination.

1101.15.1 Where Not Required. No trap shall be required for leaders or conductors that are connected to a sewer carrying storm water exclusively. 1101.15.2 Trap Size. Traps, where installed for individual conductors, shall be the same size as the horizontal drain to which they are connected.

1101.15.3 Method of Installation of Combined Sewer. Individual storm-water traps shall be installed on the stormwater drain branch serving each storm-water inlet, or a single trap shall be installed in the main storm drain just before its connection with the combined building sewer. Such traps shall be provided with an accessible cleanout on the outlet side of the trap.

CPC § 3.1 High relevance — show source text

J109.3 Interceptor drains. Interceptor drains shall be installed along the top of cut slopes receiving drainage from a tributary width greater than 40 feet (12 192 mm), measured horizontally. They shall have a minimum depth of 1 foot (305 mm) and a minimum width of 3 feet (915 mm). The slope shall be approved by the building official, but shall be not less than one unit vertical in 50 units horizontal (2-percent slope). The drain shall be paved with concrete not less than 3 inches (76 mm) in thickness, or by other materials suitable to the application. Discharge from the drain shall be accomplished in a manner to prevent erosion and shall be approved by the building official.

J109.4 Drainage across property lines. Drainage across property lines shall not exceed that which existed prior to grading. Excess or concentrated drainage shall be contained on site or directed to an approved drainage facility. Erosion of the ground in the area of discharge shall be prevented by installation of nonerosive down drains or other devices.

SECTION J110—EROSION CONTROL

J110.1 General. The faces of cut and fill slopes shall be prepared and maintained to control erosion. This control shall be permitted to consist of effective planting.

Exception: Erosion control measures need not be provided on cut slopes not subject to erosion due to the erosion-resistant character of the materials.

Erosion control for the slopes shall be installed as soon as practicable and prior to calling for final inspection.

J110.2 Other devices. Where necessary, check dams, cribbing, riprap or other devices or methods shall be employed to control erosion and provide safety.

SECTION J111—REFERENCED STANDARDS

J111.1 General. See Table J111.1 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 J111.1—REFERENCED STANDARDS	Col2	Col3
STANDARD ACRONYM	STANDARD NAME	SECTIONS HEREIN REFERENCED
ASTM D1557—12E1	Test Method for Laboratory Compaction Characteristics of Soil Using Modified Effort [56,000 ft-lb/ft3(2,700 kN-m/m3)].	J107.5
ASCE/SEI 7—22	Minimum Design Loads and Associated Criteria for Buildings and Other Structures	J104.4

2025 CALIFORNIA BUILDING CODE APPENDIX J-5

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

APPENDIX J-6 2025 CALIFORNIA BUILDING CODE

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

CALIFORNIA BUILDING CODE – MATRIX ADOPTION TABLE

APPENDIX K – GROUP R-3 AND GROUP R-3.1 OCCUPANCIES PROTECTED

BY THE FACILITIES OF THE CENTRAL VALLEY FLOOD PROTECTION PLAN

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

Frequently asked questions

Who must stamp the siphonic roof drainage calculations?

A registered design professional must prepare and stamp the engineered design per § 1106.1.

Does the CPC give the hydraulic equations for siphonic systems?

No. The CPC requires compliance with ASPE/ANSI 45 for siphonic systems (§ 1106.2); the detailed hydraulic methods are in that standard, not verbatim in the CPC.

Can I use a drain not certified to ASME A112.6.9?

No. § 1106.3 requires siphonic roof drains to comply with ASME A112.6.9; using noncompliant drains would not meet that Code requirement without AHJ-approved equivalency.

Are siphonic systems exempt from the CPC testing rules?

No. New and altered storm drainage systems, including siphonic systems, are subject to the CPC testing provisions in § 1107.

Where in the Code does it list ASPE/ANSI 45 and ASME A112.6.9?

Those standards are referenced in § 1106.2 and § 1106.3 respectively, and appear in the CPC’s referenced-standards tables (Chapter 17).

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Related in the CPC

What testing is required for new or altered storm drainage systems and acceptable methods?

What are requirements for rainwater sumps, pumps and backflow protection for subsoil drains?

Engineered storm systems, siphonic drains and testing

California Plumbing Code