CPC · California Plumbing Code

What materials are permitted for rain leaders, conductors and subsoil drains?

Short homeowner summary: The California Plumbing Code limits materials for roof downspouts and buried perimeter drains. Aboveground leaders/conductors must be one of the listed metals or approved DWV/plastic pipe types (with some agency limits on PVC/ABS); buried subsoil drains must be perforated/open‑joint pipe of **PE (ASTM F667)**, **PVC (ASTM D2729)**, or **extra‑strength vitrified clay (ASTM C4/C700)**, at least **3 inches** diameter and surrounded by **4 inches** of gravel. Always check local adoption (HCD, OSHPD) before selecting PVC/ABS.

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Last reviewed: July 6, 2026

What the code requires — plain English

The California Plumbing Code requires that materials used for leaders, conductors, and subsoil drains comply with the material lists and referenced standards in § 1101.4 and the specific material table for subsoil drains at Table 1101.4.6. Leaders and conductors installed aboveground must be one of the listed metals or listed DWV/plastic pipe types; subsoil drains must be open‑jointed or perforated and constructed of approved materials (PE, PVC or extra‑strength vitrified clay) meeting the referenced ASTM standards. § 1101.4

Use only the materials the CPC lists for each application: aboveground conductors vs. exterior leaders vs. buried subsoil drains — they are not interchangeable. § 1101.4

Requirements in detail

1) Leaders and conductors (aboveground)

Materials permitted for conductors installed aboveground in buildings include: seamless copper water tube (Type K, L or M); Schedule 40 copper pipe; DWV copper drainage tube; service‑weight cast‑iron soil pipe (including hubless cast‑iron); standard weight galvanized steel pipe; stainless steel 304 or 316L (with restrictions); and Schedule 40 ABS or Schedule 40 PVC where allowed by adoption. These materials must comply with the applicable referenced standards in the code. § 1101.4.2
Materials permitted for leaders installed outside (exterior downspouts) include metal sheet options (aluminum, galvanized steel, copper) or materials listed for aboveground DWV/pipe per the referenced standards. § 1101.4.3
Special notes from § 1101.4.2:
- Stainless steel 304: shall not be installed underground and must be kept not less than 6 inches aboveground. § 1101.4.2
- ABS/PVC limits: some agency adoptions limit or prohibit ABS/PVC (see Exceptions & special cases below). § 1101.4.2

Decision table — leaders & conductors (quick reference)

Application	Typical permitted materials	Code Reference
Aboveground building conductors	Copper (Type K/L/M, Schedule 40, DWV tube), cast‑iron (service weight/hubless), galvanized steel, stainless steel 304/316L (with elevation restriction for 304), Schedule 40 ABS/PVC (where allowed)	§ 1101.4.2
Exterior leaders (sheet metal)	Aluminum sheet metal, galvanized steel sheet metal, copper sheet metal, or pipe complying with referenced standards	§ 1101.4.3
Cleanout at conductor base	Cleanout required at base before horizontal connection to building storm sewer	§ 1101.13.1

2) Subsoil drains (buried perimeter drains)

Subsoil drains must be open‑jointed, perforated, or both, and constructed of materials in conformance with Table 1101.4.6. § 1101.4.6
Table 1101.4.6 lists permitted materials and referenced standards:
- PE (polyethylene) — ASTM F667
- PVC — ASTM D2729
- Vitrified clay (extra strength) — ASTM C4, ASTM C700
  (Table title: Materials for Subsoil Drainpipe and Fittings). Table 1101.4.6
Installation minimums (from § 1101.6, cross‑referenced in 1101.4.6):
- Minimum pipe diameter for subsoil drains: not less than 3 inches (80 mm).
- Pipe shall be laid in gravel, slag, crushed rock, approved 3/4" crushed recycled glass aggregate, or other approved porous material, with not less than 4 inches (102 mm) of that material surrounding the pipe. Exterior subsoil piping must have filter media. § 1101.6

Decision table — subsoil drains (quick reference)

Item	Required value / permitted options	Code Reference
Minimum pipe diameter	3 inches (80 mm)	§ 1101.6
Surrounding envelope	≥ 4 inches (102 mm) of gravel/approved porous material around pipe	§ 1101.6
Exterior filter	Filter media required for exterior subsoil piping	§ 1101.6
Permitted pipe materials	PE (ASTM F667), PVC (ASTM D2729), Vitrified clay extra strength (ASTM C4, C700)	Table 1101.4.6

Exceptions & special cases

Agency adoption differences:
- HCD 1: ABS or PVC installations are limited to not more than two stories of residential accommodation. (If your project is under HCD 1, PVC/ABS conductors above two residential stories are restricted.) § 1101.4.2.1
- OSHPD 1–5 (hospital facilities): ABS and PVC installations are not allowed. Check the Authority Having Jurisdiction for state‑agency adoption that applies to your project. § 1101.4.2.2
Stainless steel 304: do not bury stainless 304 pipe; it must remain ≥ 6 inches abovegrade where used. § 1101.4.2
Leaders, conductors, and soil/waste/vent pipes are not interchangeable — a leader cannot be used as a soil/waste/vent pipe and vice versa. § 1101.16

Common mistakes

Installing stainless steel 304 underground (some designers do this for corrosion resistance — the code forbids burying 304). § 1101.4.2
Using PVC/ABS on hospital projects or where the adopting agency forbids it — check jurisdictional adoption notes (HCD/OSHPD). § 1101.4.2.1, 1101.4.2.2
Forgetting the cleanout at the base of a rain leader/conductor that connects to a building storm sewer. § 1101.13.1
Using a soil stack or DWV soil pipe as a leader or conductor (or vice versa). § 1101.16
Installing subsoil drains without the required 4‑inch granular envelope or using non‑permitted pipe materials (must match Table 1101.4.6). § 1101.6, Table 1101.4.6

Worked example — residential basement perimeter drain

Scenario: A two‑story single‑family residence with a basement requires a perimeter subsoil drain and downspouts from the roof.

Subsoil drain:
- Choose 3‑inch perforated PE pipe listed to ASTM F667. This matches Table 1101.4.6 (PE / ASTM F667). Table 1101.4.6
- Provide ≥ 4 inches of crushed rock around the pipe and filter media for exterior discharge. This meets the installation requirements of § 1101.6. § 1101.6
Rain leaders/conductors:
- Roof downspouts from this two‑story residential building: Schedule 40 PVC conductors are permissible if the municipality/adopting agency does not prohibit PVC and the project qualifies under HCD limits (HCD allows PVC/ABS for residential accommodation up to two stories). Since this is exactly two stories, Schedule 40 PVC is permitted by § 1101.4.2.1 (subject to local adoption). § 1101.4.2.1
- Add a cleanout at the base of each leader before it connects to the horizontal storm drain per § 1101.13.1. § 1101.13.1

If the project were a hospital (OSHPD), replace PVC with an approved metallic conductor (copper, cast iron, galvanized steel, etc.) because OSHPD adoption disallows ABS/PVC. § 1101.4.2.2

Related provisions (useful cross‑references)

§ 1101.6 — Subsoil drains: minimum diameter, bedding and filter media requirements.
§ 1101.13.1 — Cleanout at base of rain leaders/conductors.
§ 1101.15 — Traps on storm drains and leaders (when required).
§ 1101.16 — Leaders, conductors, and connections (non‑interchangeability and protection).
§ 1102.1 — Roof drains: permitted materials and standards (useful when selecting roof‑drain bodies that connect to leaders).
§ 1103.1 — Sizing of vertical conductors and leaders (use Table 1103.1 for sizing).

Code references

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

CPC § 1101.4.2.2 High relevance — show source text
1101.4.2.2 [OSHPD 1, 2, 3, 4 & 5] ABS and PVC installations are not allowed.

1101.4.3 Leaders. Leaders installed outside shall comply with the applicable standards referenced in Table 701.2 for aboveground drain, waste, and vent pipe; aluminum sheet metal; galvanized steel sheet metal; or copper sheet metal. 1101.4.4 Underground Building Storm Drains. Underground building storm drains shall comply with the applicable standards referenced in Table 701.2 for underground drain, waste, and vent pipe. 1101.4.5 Building Storm Sewers. Building storm sewers shall comply with the applicable standards referenced in Table 701.2 for building sewer pipe. 1101.4.6 Subsoil Drains. Subsoil drains shall be open jointed, perforated, or both and constructed of materials in conformance with Table 1101.4.6.

TABLE 1101.4.6

MATERIALS FOR SUBSOIL DRAINPIPE AND FITTINGS

MATERIAL REFERENCED STANDARD(S)

PE ASTM F667

PVC ASTM D2729

Vitrified Clay (Extra strength) ASTM C4, ASTM C700

1101.5 Expansion Joints Required. Expansion joints or sleeves shall be provided where warranted by temperature variations or physical conditions. 1101.6 Subsoil Drains. Subsoil drains shall be provided around the perimeter of buildings having basements, cellars, crawl spaces, or floors below grade. Such subsoil drains shall be permitted to be positioned inside or outside of the footing, shall be of perforated or open-jointed approved drain tile or pipe, not less than 3 inches (80 mm) in diameter, and shall be laid in gravel, slag, crushed rock, approved [3] ⁄ 4 of an inch (19.1 mm) crushed, recycled glass aggregate, or other approved porous material with not less than 4 inches (102 mm) surrounding the pipe. Filter media shall be provided for exterior subsoil piping. Exception: [HCD 1 & HCD 2] Subsoil drains are mandatory only when required by the Authority Having Jurisdiction due to geological conditions.

TABLE 1101.4.6

MATERIALS FOR SUBSOIL DRAINPIPE AND FITTINGS

2025 CALIFORNIA PLUMBING CODE 205

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STORM DRAINAGE

1101.6.1 Discharge. Subsoil drains shall be piped to a storm drain, to an approved water course, to the front street curb or gutter, to an alley, or the discharge from the subsoil drains shall be conveyed to the alley by a concrete gutter. Where a continuously flowing spring or groundwater is encountered, subsoil drains shall be piped to a storm drain or an approved water course. 1101.6.2 Sump. Where it is not possible to convey the drainage by gravity, subsoil drains shall discharge to an accessible sump provided with an approved automatic electric pump.
CPC § 1101.4.1 High relevance — show source text
Mounting methods, supports and sample sizes of materials for testing that are not specified in ASTM E84 or UL 723 shall be prohibited.

[HCD 1 & HCD 2] ABS or PVC installations are limited to not more than two stories of areas of residential accommo- dation.

[OSHPD 1, 2, 3, 4 & 5] ABS and PVC installations are not allowed.

1101.4.1 Copper and Copper Alloys. Joints and connections in copper and copper alloy pipe and tube shall be installed in accordance with Section 705.3.

1101.4.2 Conductors. Conductors installed aboveground in buildings shall comply with the applicable standards referenced in Table 701.2 for aboveground drain, waste, and vent pipe. Conductors installed aboveground level shall be of seamless copper water tube, Type K, L, or M; Schedule 40 copper pipe or Schedule

40 copper alloy pipe; Type DWV copper drainage tube; service weight cast-iron soil pipe or hubless cast-iron soil pipe; standard weight galvanized steel pipe; stainless steel 304 or 316L [stainless steel 304 pipe and fittings shall not be installed underground and shall be kept not less than 6 inches (152 mm) aboveground], or Schedule 40 ABS or Schedule 40 PVC plastic pipe. 1101.4.2.1 [HCD 1] ABS or PVC installations are limited to not more than two stories of areas of res- idential accommodation.

1101.4.2.2 [OSHPD 1, 2, 3, 4 & 5] ABS and PVC installations are not allowed.

1101.4.3 Leaders. Leaders installed outside shall comply with the applicable standards referenced in Table 701.2 for aboveground drain, waste, and vent pipe; aluminum sheet metal; galvanized steel sheet metal; or copper sheet metal. 1101.4.4 Underground Building Storm Drains. Underground building storm drains shall comply with the applicable standards referenced in Table 701.2 for underground drain, waste, and vent pipe. 1101.4.5 Building Storm Sewers. Building storm sewers shall comply with the applicable standards referenced in Table 701.2 for building sewer pipe. 1101.4.6 Subsoil Drains. Subsoil drains shall be open jointed, perforated, or both and constructed of materials in conformance with Table 1101.4.6.

TABLE 1101.4.6

MATERIALS FOR SUBSOIL DRAINPIPE AND FITTINGS

MATERIAL REFERENCED STANDARD(S)

PE ASTM F667

PVC ASTM D2729

Vitrified Clay (Extra strength) ASTM C4, ASTM C700

1101.5 Expansion Joints Required. Expansion joints or sleeves shall be provided where warranted by temperature variations or physical conditions. 1101.6 Subsoil Drains. Subsoil drains shall be provided around the perimeter of buildings having basements, cellars, crawl spaces, or floors below grade.
CPC § 1101.13.1 High relevance — show source text
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.

1101.16 Leaders, Conductors, and Connections. Leaders or conductors shall not be used as soil, waste, or vent pipes nor shall soil, waste, or vent pipes be used as leaders or conductors.

1101.16.1 Protection of Leaders. Leaders installed along alleyways, driveways, or other locations where exposed to damage shall be protected by metal guards, recessed into the wall, or constructed from the ferrous pipe. 1101.16.2 Combining Storm with Sanitary Drainage. The sanitary and storm drainage system of a building shall be entirely separate, except where a combined sewer is used, in which case the building storm drain shall be connected in the same horizontal plane through a single wye fitting to the combined building sewer not less than 10 feet (3048 mm) downstream from a soil stack.

1102.0 Roof Drains.

1102.1 Applications. Roof drains shall be constructed of aluminum, cast-iron, copper alloy of not more than 15 percent zinc, leaded nickel bronze, stainless steel, ABS, PVC, polypropylene, polyethylene, or nylon and shall comply with ASME A112.3.1 or ASME A112.6.4.

1102.2 Dome Strainers Required. Roof drains shall have domed strainers.

Exception: Roof drain strainers for use on sun decks, parking decks, and similar areas that are normally serviced and maintained, shall be permitted to be of the flat surface type. Such roof drain strainers shall be level with the deck.
CPC § 1101.1 High relevance — show source text
1101.1 Applicability . . . . . . . . . . . . . . . . . .205

1101.2 Where Required . . . . . . . . . . . . . .205

1101.3 Storm Water Drainage to Sanitary Sewer Prohibited . . . . . .205

1101.4 Material Uses . . . . . . . . . . . . . . . .205

Table 1101.4.6 Materials for Subsoil Drainpipe and Fittings . . . . . . . . . . . . . . . . . .205

1101.5 Expansion Joints Required . . . . . .205

1101.6 Subsoil Drains . . . . . . . . . . . . . . .205

1101.7 Building Subdrains . . . . . . . . . . . .206

1101.8 Areaway Drains . . . . . . . . . . . . . .206

1101.9 Window Areaway Drains . . . . . . .206

1101.10 Filling Stations and Motor Vehicle Washing Establishments . . . . . . . . . . . . . . .206

1101.11 Paved Areas . . . . . . . . . . . . . . . . .206

1101.12 Roof Drainage . . . . . . . . . . . . . . .206

1101.13 Cleanouts . . . . . . . . . . . . . . . . . . .207

1101.14 Rainwater Sumps . . . . . . . . . . . . .207

1101.15 Traps on Storm Drains and Leaders . . . . . . . . . . . . . . . . . . . . .207

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
CPC § 1101.16 High relevance — show source text
1101.16 Leaders, Conductors, and Connections. Leaders or conductors shall not be used as soil, waste, or vent pipes nor shall soil, waste, or vent pipes be used as leaders or conductors.

1101.16.1 Protection of Leaders. Leaders installed along alleyways, driveways, or other locations where exposed to damage shall be protected by metal guards, recessed into the wall, or constructed from the ferrous pipe. 1101.16.2 Combining Storm with Sanitary Drainage. The sanitary and storm drainage system of a building shall be entirely separate, except where a combined sewer is used, in which case the building storm drain shall be connected in the same horizontal plane through a single wye fitting to the combined building sewer not less than 10 feet (3048 mm) downstream from a soil stack.

1102.0 Roof Drains.

1102.1 Applications. Roof drains shall be constructed of aluminum, cast-iron, copper alloy of not more than 15 percent zinc, leaded nickel bronze, stainless steel, ABS, PVC, polypropylene, polyethylene, or nylon and shall comply with ASME A112.3.1 or ASME A112.6.4.

1102.2 Dome Strainers Required. Roof drains shall have domed strainers.

Exception: Roof drain strainers for use on sun decks, parking decks, and similar areas that are normally serviced and maintained, shall be permitted to be of the flat surface type. Such roof drain strainers shall be level with the deck.

1102.3 Roof Drain Flashings. The connection between the roof and roof drains that pass through the roof and into the interior of the building shall be made watertight by the use of proper flashing material. 1102.3.1 Lead Flashing. Where lead flashing material is used, it shall be not less than 4 pounds per square foot (lb/ft [2] ) (19 kg/m [2] ). 1102.3.2 Copper Flashing. Where copper flashing material is used, it shall be not less than 12 ounces per square foot (oz/ft [2] ) (3.7 kg/m [2] ).

1103.0 Size of Leaders, Conductors, and Storm Drains.

1103.1 Vertical Conductors and Leaders. Vertical conductors and leaders shall be sized by the maximum projected roof area and Table 1103.1.

1103.2 Size of Horizontal Storm Drains and Sewers. The size of building storm drains, or building storm sewers or their horizontal branches shall be based on the maximum projected roof or paved area to be handled and Table 1103.2.

1103.3 Size of Roof Gutters. The size of semi-circular gutters shall be based on the maximum projected roof area and Table 1103.3.

1103.4 Side Walls Draining onto a Roof. Where vertical walls project above a roof to permit storm water to drain into the roof area below, the adjacent roof area shall be permitted to be computed from Table 1103.1 as follows:

(1) For one wall – add 50 percent of the wall area to the roof area figures.

(2) For two adjacent walls of equal height – add 35 percent of the total wall areas.

2025 CALIFORNIA PLUMBING CODE 207
California Plumbing Code High relevance — show source text
|100 psf|1 hr
23 min|||7|1, 2|11/3| |F/C-4-RC-9|4″|4″ deep (4370 psi);1/4″ reinforcement bars
at 6″ pitch with3/4″ cover;1/4″ main rein-
forcement bars at 4″ pitch perpendicular
with1/2″ cover; 13′1″ span restrained.|150 psf|2 hrs|||7|1, 3|2| |F/C-4-RC-10|4″|4″ thick (5140 psi) deck;1/4″ reinforce-
ment bars at 71/2″ pitch with7/8″ cover;3/8″
main reinforcement bars at 33/4″ pitch
perpendicular with1/2″ cover; 13′1″ span
restrained.|140 psf|1 hr
16 min|||7|1, 5|11/4| |F/C-4-RC-11|4″|4″ thick (4000 psi) concrete deck;
3″ × 11/2″ × 4 lbs R.S.J.; 2′6″ C.R.S.; flush
with top surface; 4″ × 6″ x 13 SWG mesh
reinforcement 1″ from bottom of slab; 6′6″
span restrained.|150 psf|2 hrs|||7|1, 3|2| |F/C-4-RC-12|4″|4″ deep (2380 psi) concrete deck;
3″ × 11/2″ × 4 lbs R.S.J.; 2′6″ C.R.S.; flush
with top surface; 4″ × 6″ x 13 SWG mesh
reinforcement 1″ from bottom surface;
6′6″ span restrained.|150 psf|1 hr
3 min|||7|1, 2|1| |F/C-4-RC-13|41/2″|41/2″ thick (5200 psi) deck;1/4″ reinforce-
ment bars at 71/4″ pitch with7/8″ cover;3/8″
main reinforcement bars at 33/4″ pitch
perpendicular with1/2″ cover; 13′1″ span
restrained.|140 psf|2 hrs|||7|1, 3|2| |F/C-4-RC-14|41/2″|41/2″ deep (2525 psi) concrete deck;1/4″
reinforcement bars at 71/2″ pitch with7/8″
cover;3/8″ main reinforcement bars at
33/8″ pitch perpendicular with1/2″ cover;
13′1″ span restrained.|150 psf|42 min|||7|1, 5|2/3| |F/C-4-RC-15|41/2″|41/2″ deep (4830 psi) concrete deck;
11/2″ × No.
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

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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 § 102.0 High relevance — show source text
downspouts, and roof washers.|Every 6 months| |Inspect and clear debris from the roof or other aboveground rainwater collection
surface.|Every 6 months| |Remove tree branches and vegetation overhanging roof or other aboveground rain-
water collection surface.|As needed| |Inspect pumps and verify operation.|After initial installation and every 12 months thereafter| |Inspect valves and verify operation.|After initial installation and every 12 months thereafter| |Inspect pressure tanks and verify operation.|After initial installation and every 12 months thereafter| |Clear debris and inspect storage tanks, locking devices, and verify operation.|After initial installation and every 12 months thereafter| |Inspect caution labels and marking.|After initial installation and every 12 months thereafter|

K 102.0 Connection.

K 102.1 General. No water piping supplied by a potable rainwater catchment system shall be connected to a source of supply without the approval of the Authority Having Jurisdiction, Health Department, or other department having jurisdiction.

K 102.2 Connections to Public or Private Potable Water Systems. Potable rainwater catchment systems shall have no direct connection to a public or private potable water supply or alternate water source system. Potable water from a public or private potable water system is permitted to be used as makeup water to the rainwater storage tank provided the public, or private potable water supply connection is protected by an air gap or reduced-pressure principle backflow preventer in accordance with this code. K 102.3 Backflow Prevention. The potable rainwater catchment system shall be protected against backflow in accordance with this code.

K 103.0 Potable Rainfall Catchment System Materials.

K 103.1 Collections Surfaces. The collection surface for potable applications shall be constructed of a hard, impervious material and shall be approved for potable water use. Roof coatings, paints, and liners shall comply with NSF Protocol P151. K 103.1.1 Prohibited. Roof paints and coatings with lead, chromium, or zinc shall not be permitted. Wood roofing material and lead flashing shall not be permitted. K 103.2 Rainwater Catchment System Drainage Materials. Materials used in rainwater catchment drainage systems, including gutters, downspouts, conductors, and leaders shall be in accordance with the requirements of this code for storm drainage.

K 103.3 Storage Tanks. Rainwater storage shall comply with Section K 105.0.

K 103.4 Water Supply and Distribution Materials. Potable rainwater supply and distribution materials shall comply with the requirements of this code for potable water supply and distribution systems.

K 104.0 Design and Installation.

K 104.1 Collection Surfaces. Rainwater shall be collected from a roof or other cleanable aboveground surfaces specifically designed for rainwater catchment. A rainwater catchment system shall not collect rainwater from:

(1) Vehicular parking surfaces

(2) Surface water runoff

(3) Bodies of standing water

K 104.2 Prohibited Discharges. Overflows, condensate, and bleed-off pipes from roof-mounted equipment and appliances shall not discharge onto roof surfaces that are intended to collect rainwater.
CPC § 1602.6 High relevance — show source text
The test shall be ruled successful by the Authority Having Jurisdiction before final approval is granted. 1602.6 Sizing. The design and size of rainwater drains, gutters, conductors, and leaders shall comply with Chapter 11 of this code.

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NONPOTABLE RAINWATER CATCHMENT SYSTEMS

1602.7 Rainwater Catchment System Materials. Rain- 1603.3 Rainwater Catchment Collection Surfaces. water catchment system materials shall comply with Section Rainwater shall be collected from roof surfaces or other 1602.7.1 through Section 1602.7.3 . impervious manmade, aboveground collection surfaces. 1602.7.1 Water Supply and Distribution Materi- 1603.3.1 Other Surfaces. Natural precipitation colals. Rainwater catchment water supply and distribution lected from surface water runoff, vehicular parking surmaterials shall comply with the requirements of this code faces, or manmade surfaces at or below grade shall be in for potable water supply and distribution systems unless accordance with the water quality requirements for onotherwise provided for in this section. site treated nonpotable gray water systems in Section

1506.0.

1602.7.2 Rainwater Catchment System Drainage Materials. Materials used in rainwater catchment Exception: Collected rainwater or storm water used

exclusively for subsurface landscape irrigation.

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

1602.7.3 Storage Tanks. Rainwater storage tanks shall

intended to collect rainwater without prior approval from

comply with Section 1603.5.

the Authority Having Jurisdiction.

1602.8 Rainwater Catchment System Color and

1603.4 Minimum Water Quality. The minimum water

Marking Information. Rainwater catchment systems shall

quality for harvested rainwater shall meet the applicable water

have a colored background in accordance with Section 601.3.

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

mined by the Authority Having Jurisdiction. In the absence of

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

ing Jurisdiction, the minimum treatment and water quality
CPC § 2.4 High relevance — show source text
The vent terminal shall be directed downward and covered with a [3] ⁄ 32 of an inch (2.4 mm) mesh screen to prevent the entry of vermin and insect.

K 105.11 Pumps. Pumps serving rainwater catchment systems shall be listed for potable water use. Pumps supplying water to water closets, urinals, and trap primers shall be capable of delivering not less than the minimum residual pressure required by the highest and most remote outlet served. Where the water pressure in the rainwater supply system within the building exceeds 80 psi (552 kPa), a pressure reducing valve reducing the pressure to 80 psi (552 kPa) or less to water outlets in the building shall be installed in accordance with this code.

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

K 106.0 Freeze Protection.

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

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

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

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

K 107.0 Cleaning. K 107.1 General. The interior surfaces of tanks and equipment shall be clean before they are put into service.
CPC § 3.00 High relevance — show source text
120" diameter nail|12|3.00|0.70|DR|DR|2.15|DR|DR|DR| |Wood Framing
(minimum 11/4- inch
penetration)b|0.131" diameter nail|6|4.00|2.15|1.20|0.75|4.00|1.35|0.70|DR| |Wood Framing
(minimum 11/4- inch
penetration)b|0.131" diameter nail|8|4.00|1.55|0.80|DR|4.00|0.90|DR|DR| |Wood Framing
(minimum 11/4- inch
penetration)b|0.131" diameter nail|12|4.00|0.90|DR|DR|2.70|0.50|DR|DR| |Wood Framing
(minimum 11/4- inch
penetration)b|0.162" diameter nail|6|4.00|3.55|2.05|1.40|4.00|2.25|1.25|0.80| |Wood Framing
(minimum 11/4- inch
penetration)b|0.162" diameter nail|8|4.00|2.55|1.45|0.95|4.00|1.60|0.85|0.50| |Wood Framing
(minimum 11/4- inch
penetration)b|0.162" diameter nail|12|4.00|1.60|0.85|0.50|4.00|0.95|DR|DR| |For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa.
DR = Design Required, o.c. = on center.
a. Wood framing shall be spruce-pine-fir or any wood species with a specific gravity of 0.42 or greater in accordance with ANSI/AWC NDS.
b. The thickness of wood structural panels complying with the specific gravity requirement of Note a shall be permitted to be included in satisfying the minimum penetration
into framing.
c. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
d. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.|For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa.
DR = Design Required, o.c. = on center.
a. Wood framing shall be spruce-pine-fir or any wood species with a specific gravity of 0.42 or greater in accordance with ANSI/AWC NDS.
b. The thickness of wood structural panels complying with the specific gravity requirement of Note a shall be permitted to be included in satisfying the minimum penetration
into framing.
c. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
d. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.|For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa.
DR = Design Required, o.c. = on center.
a.
CPC § 106.2.1 High relevance — show source text
K 106.2.1 Size. The roof washer shall be sized to direct rainwater containing debris that has accumulated on the collection surface away from the storage tank. ARCSA/ASPE/ANSI 63 contains additional guidance on acceptable methods of sizing roof washers.

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

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

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

K 108.0 Supply System Inspection and Test. K 108.1 General. Rainwater catchment systems shall be inspected and tested in accordance with the applicable provisions of this code for testing of potable water and storm drainage systems. Storage tanks shall be filled with water to the overflow opening for 24 hours, and during the inspection, or by other means as approved by the Authority Having Jurisdiction. Seams and joints shall be exposed during the inspection and checked for water tightness.

496 2025 CALIFORNIA PLUMBING CODE

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

CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE

APPENDIX L - SUSTAINABLE PRACTICES

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

Frequently asked questions

Can I use PVC for exterior downspouts?

Yes — PVC listed to the referenced standards is permitted for leaders/conductors in general, but check local agency adoption: HCD limits PVC/ABS to not more than two stories of residential accommodation and OSHPD adoptions prohibit ABS/PVC in certain hospital facilities. § 1101.4.2.1, § 1101.4.2.2

What pipe sizes are required for subsoil drains?

Subsoil drains shall be not less than 3 inches (80 mm) in diameter and must be open‑jointed or perforated, laid in approved granular material with ≥ 4 inches (102 mm) surrounding the pipe. § 1101.6

Are stainless steel leaders allowed underground?

No. Stainless steel 304 shall not be installed underground and must be kept at least 6 inches aboveground where used; 316L is listed as permitted for conductors. § 1101.4.2

Do I need a cleanout where the downspout meets the storm drain?

Yes — a cleanout is required at the base of the leader or conductor before it connects to the horizontal building storm sewer. § 1101.13.1

If my project is under OSHPD, can I use ABS/PVC conductors?

No — OSHPD adoptions disallow ABS and PVC installations for those facilities. Check the Authority Having Jurisdiction for exact application. § 1101.4.2.2

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