CPC · California Plumbing Code

Floor drain and building trap special requirements

Q: Can I install a building trap whenever I want?

No — building traps are prohibited unless required by the Authority Having Jurisdiction (AHJ) . If the AHJ requires one, it must have an accessible cleanout and a relieving vent/fresh‑air intake per § 1008.1 .

Q: When does a floor drain need a backwater valve?

If the floor drain is subject to reverse flow of sewage or liquid waste , the drain must be equipped with an approved backwater valve per § 1006.1 .

Q: Do I have to protect rarely used floor drains from evaporation?

Yes — floor drains and similar traps that are directly connected and subject to infrequent use should be protected with a trap seal primer unless the AHJ determines it’s unnecessary; primers must be accessible for maintenance (§ 1007.1–1007.2) .

Q: What size can the relieving vent (fresh‑air intake) for a building trap be?

The code limits that relieving vent or fresh‑air intake to no larger than one‑half the diameter of the drain to which it connects, and it must be carried above grade to a screened outlet outside the building (§ 1008.1) .

Q: Does the drain inlet have to be visible?

Yes — § 1006.1 requires the drain inlet be so located that it is in full view , to facilitate inspection and maintenance .

In plain terms: the California Plumbing Code requires every floor drain to tie into a trap that can be cleaned and is properly sized, with the drain inlet visible; if the drain can get reverse sewage it needs a backwater valve. Building traps are only allowed if the local authority requires them, and when used they must have a cleanout and a small relieving vent taken above grade to a screened outlet outside the building (see §1006.1 and §1008.1) .

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Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

Floor drains must connect to a trap that is readily cleanable and sized to serve the drain, and the drain inlet must be in full view; where subject to sewer reverse flow the drain must be protected by an approved backwater valve (see § 1006.1). Building traps are not permitted except where the AHJ requires them, and when installed each building trap must have an accessible cleanout and a relieving vent or fresh‑air intake on the inlet side — that relieving vent may be no larger than one‑half the diameter of the drain to which it connects and must be carried above grade to a screened outlet outside the building (see § 1008.1) .

The single most important rule: floor drains must be trapped with a cleanable trap and made visible; building traps are only allowed when required and must have a cleanout plus a small relieving vent terminating outside the building (§ 1006.1; § 1008.1) .

Requirements in detail

1) Floor drain traps (controlling text: § 1006.1)

The floor drain must connect into a trap that is constructed to be readily cleaned and sized to serve the intended purpose. The drain inlet must be in full view. If the drain is exposed to possible reverse sewage or liquid waste flow, an approved backwater valve is required .
Related trap-seal protection: floor drains or similar traps that are directly connected and subject to infrequent use generally require a trap seal primer (see § 1007.1) .

2) Building trap special requirements (controlling text: § 1008.1)

Building traps shall not be installed except where required by the Authority Having Jurisdiction (AHJ). When installed, each building trap must have:
- an accessible cleanout, and
- a relieving vent or fresh‑air intake on the inlet side of the trap.
The relieving vent/fresh‑air intake:
- Need not be larger than one‑half the diameter of the drain to which it connects, and
- Shall be carried above grade and terminate in a screened outlet located outside the building .

3) Sizing and trap details (supporting CPC text)

Floor drain minimum trap and DFU guidance are given elsewhere in the code (floor drains commonly use 2‑inch minimum trap and trap arm per fixture tables; trap sizing examples are found in B 101.5) — see table below for decision‑relevant dimensions and references file.

Quick reference table (decision‑relevant values)

Requirement	Value / threshold	Code Reference
Trap must be cleanable	Readily constructed so it can be cleaned	§ 1006.1
Drain inlet visibility	In full view (visible)	§ 1006.1
Backwater protection	Required when subject to reverse flow	§ 1006.1
Building trap allowed?	Only when AHJ requires	§ 1008.1
Building trap cleanout	Accessible cleanout required on trap	§ 1008.1
Relieving vent / fresh‑air intake size	≤ one‑half the diameter of the drain	§ 1008.1
Relieving vent termination	Carried above grade, screened outlet outside building	§ 1008.1
Trap seal depth (general trap requirement)	Not less than 2 in. and not more than 4 in. (unless AHJ requires deeper)	§ 1005.1
Typical floor drain minimum trap size (practical example)	2 in. minimum; traps commonly sized per Table/B 101.5 examples (3" drain → 4" trap)	B 101.5 example; § 702.1 DFU table file

Exceptions & special cases

Local authority (AHJ) discretion: the AHJ may choose not to require a building trap; building traps otherwise are prohibited unless required by the AHJ (§ 1008.1) .
Trap‑seal protection: floor drains that are directly connected and infrequently used should be protected with a trap seal primer unless the AHJ deems it unnecessary; primers must be accessible for maintenance (§ 1007.1–1007.2) .
Industry‑specific requirements: certain occupancies (meat and poultry processing, slaughterhouses, etc.) require deep‑seal traps or other special trap configurations; the code contains specific sections addressing those occupancies (e.g., § 1010.2.1 requires deep‑seal traps for meat and poultry processing plants) .
Storm/storm–sanitary combinations: leaders and storm drains where connected to a combined sewer are trapped per separate storm‑drain rules; see storm drainage provisions for exceptions and trap sizing for leaders (§ 1101.15 et seq.) .

Common mistakes

Installing a building trap by default (rather than only when required by the AHJ). Building traps are disfavored and strictly limited (§ 1008.1) .
Omitting an accessible cleanout on the building trap; the code explicitly requires a cleanout when a building trap is present (§ 1008.1) .
Failing to make the floor drain inlet visible (in full view) — drains buried or hidden can prevent inspection and maintenance and conflict with § 1006.1’s visibility requirement .
Not protecting infrequently used traps from evaporation (no trap primer) — trap seals can dry and allow sewer gas unless a primer or other protection is provided (§ 1007.1) .
Wrongly sizing the relieving vent: the code limits the relieving vent/fresh‑air intake to no larger than one‑half the diameter of the drain to which it connects; do not oversize that connection (§ 1008.1) .
Overlooking backflow exposure: if a floor drain could experience reverse sewage flow, an approved backwater valve is required per § 1006.1 .

Worked example — commercial laundry room with a 3‑inch floor drain

Scenario: a commercial laundry room floor drain is specified as a 3‑inch floor drain. The design must meet CPC rules for floor drains and building traps.

Steps and code grounding:

Trap connection and cleanability — provide a trap that is readily cleaned and sized to serve the drain, per § 1006.1 .
Trap sizing — the guidance/example in the code explains that a 3‑inch floor drain would normally require a 4‑inch trap when increasing trap size (B 101.5 sizing example: 3" drain → 4" trap) — use that sizing logic unless local tables require otherwise .
Trap seal depth — ensure the trap provides a liquid seal within the typical 2–4 inch range, unless AHJ requires deeper (§ 1005.1) .
Drain inlet visibility — install the floor grate so the drain inlet is in full view, per § 1006.1 .
Backwater exposure — if the laundry floor drain is on a lower level or in a location susceptible to reverse flow from the sewer, include an approved backwater valve in the drainage line per § 1006.1 .
Building trap? — do not add a building trap unless the AHJ requires one. If a building trap is installed, provide an accessible cleanout and a relieving vent/fresh‑air intake on the inlet side sized no larger than one‑half the drain diameter (if the drain is 3", relieving vent max = 1.5" nominal), and carry that intake above grade to a screened outlet outside per § 1008.1 .
If the trap will be used infrequently, provide a trap seal primer accessible for maintenance per § 1007.1–1007.2 .

Related provisions (select CPC sections)

§ 1006.1 — Floor drains: trap connection, cleanability, inlet visibility, backwater valve requirement
§ 1008.1 — Building traps: AHJ permission, cleanout, relieving vent/fresh‑air intake size and termination
§ 1007.1 / § 1007.2 — Trap seal primers and performance standards (accessibility, ASSE references)
§ 1005.1 — Trap seal depth requirements (2 in. minimum, 4 in. maximum unless AHJ requires deeper)
B 101.5 (sizing examples) — Examples showing typical trap increases for floor drains (3" drain → 4" trap) and tailpiece guidance
§ 418.1 — Floor drain fixture standards (ASME/CSA product standards and strainer requirements)
§ 1101.15 — Traps on storm drains and leaders (when applicable)
§ 1010.2.1 — Special requirement for deep‑seal traps in meat and poultry processing plants (example of occupancy‑specific rules)

Code references

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

CPC § 1004.2 High relevance — show source text
1004.2 Movable Parts. Bladders, check valves or another type of devices with moveable parts shall be prohibited to serve as a trap.

1005.0 Trap Seals. 1005.1 General. Each fixture trap shall have a liquid seal of not less than 2 inches (51 mm) and not more than 4 inches (102 mm), except where a deeper seal is found necessary by the Authority Having Jurisdiction. Traps shall be set true with respect to their liquid seals and, where necessary, they shall be protected from freezing.

1006.0 Floor Drain Traps. 1006.1 General. Floor drains shall connect into a trap so constructed that it can be readily cleaned and of a size to serve efficiently the purpose for which it is intended. The drain inlet shall be so located that it is in full view. Where subject to the reverse flow of sewage or liquid waste, such drains shall be equipped with an approved backwater valve.

1007.0 Trap Seal Protection. 1007.1 General. Floor drain or similar traps directly connected to the drainage system and subject to infrequent use shall be protected with a trap seal primer, except where not deemed necessary for safety or sanitation by the Authority Having Jurisdiction. Trap seal primers shall be accessible for maintenance.

1007.2 Trap Seal Primers. Potable water supply trap seal primer valves shall comply with ASSE 1018. Drainage or electronic design type trap seal primer devices shall comply with ASSE 1044 or IAPMO PS 76.

1008.0 Building Traps. 1008.1 General. Building traps shall not be installed except where required by the Authority Having Jurisdiction. Each building trap where installed shall be provided with a cleanout and with a relieving vent or fresh-air intake on the inlet side of the trap, which needs not be larger than one-half the diameter of the drain to which it connects. Such relieving vent or fresh-air intake shall be carried above grade and terminate in a screened outlet located outside the building.

1009.0 Interceptors (Clarifiers) and Separators.

1009.1 Where Required. Interceptors (clarifiers) (including grease, oil, sand, solid interceptors, etc.) shall be required

by the Authority Having Jurisdiction where they are necessary for the proper handling of liquid wastes containing grease, flammable wastes, sand, solids, acid or alkaline substances, or other ingredients harmful to the building drainage system, the public or private sewer, or to public or private sewage disposal. A list of acceptable interceptor standards is referenced in Table 1009.1.

TABLE 1009.1 APPROVED INTERCEPTORS (CLARIFIERS)
CPC § 101.5 High relevance — show source text
B 101.5 Trap Sizes. Trap sizes are required to be equivalent to the branches they serve (two pipe sizes larger than normal), and tailpieces between fixtures or floor drains and such traps shall be reduced to normal size.

B 101.6 Layout Drawings. Duplicate layout drawings of each such proposed piping system shall be presented to the Authority Having Jurisdiction and approval obtained before an installation is made. Complicated layouts shall be checked by qualified personnel. B 101.6.1 Example of Sizing. A floor drain normally requires a 2 inch (50 mm) trap and waste. On a combination waste and vent system, both trap and waste shall be increased two pipe sizes (through 2 [1] ⁄ 2 inches and 3 inches) (65 mm and 80 mm), which would make the trap 3 inches (80 mm). Pipe sizes recognized for this purpose are 2 inches, 2 [1] ⁄ 2 inches, 3 inches, 3 [1] ⁄ 2 inches, 4 inches, 4 [1] ⁄ 2 inches, 5 inches, 6 inches, etc. (50 mm, 65 mm, 80 mm, 90 mm, 100 mm, 115 mm, 125 mm, 150 mm, etc.). The tailpiece between the floor drain and its trap shall be 2 inches (50 mm) (or normal size) to ensure that the amount of wastewater entering the trap partially fills the waste branch. A 3 inch (80 mm) floor drain would thus require a 4 inch (100 mm) trap, and a 4 inch (100 mm) floor drain would require a 5 inch (125 mm) trap for the reasons previously stated.

WHERE IN DOUBT, CHECK WITH YOUR LOCAL Authority Having Jurisdiction.

2025 CALIFORNIA PLUMBING CODE 383

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CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE

APPENDIX C - ALTERNATE PLUMBING SYSTEMS

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

CPC § 1.11.0. High relevance — show source text

Pipe sizes recognized for this purpose are 2 inches, 2 [1] ⁄ 2 inches, 3 inches, 3 [1] ⁄ 2 inches, 4 inches, 4 [1] ⁄ 2 inches, 5 inches, 6 inches, etc. (50 mm, 65 mm, 80 mm, 90 mm, 100 mm, 115 mm, 125 mm, 150 mm, etc.). The tailpiece between the floor drain and its trap shall be 2 inches (50 mm) (or normal size) to ensure that the amount of wastewater entering the trap partially fills the waste branch. A 3 inch (80 mm) floor drain would thus require a 4 inch (100 mm) trap, and a 4 inch (100 mm) floor drain would require a 5 inch (125 mm) trap for the reasons previously stated.

WHERE IN DOUBT, CHECK WITH YOUR LOCAL Authority Having Jurisdiction.

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CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE

APPENDIX C - ALTERNATE PLUMBING SYSTEMS

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

Adopting Agency	BSC	BSC- CG	SFM	HCD	Col6	Col7	DSA	Col9	Col10	OSHPD	Col12	Col13	Col14	Col15	Col16	Col17	BSCC	DPH	AGR	DWR	CEC	CA	SL	SLC
Adopting Agency	BSC	BSC- CG	SFM	1	2	1-AC	AC	SS	SS/CC	1	1R	2	3	4	5	6	6	6	6	6	6	6	6	6
Adopt Entire Chapter
Adopt Entire Chapter as amended (amended sections listed below)
Adopt only those sections that are listed below
Chapter/Section

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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CPC § 1010.2.3 High relevance — show source text
Exception: Floor drains in areas not regularly washed down will be acceptable with deep-seal traps, provided that such drains are connected to secondary drainage systems discharging into a safe sink or basin (air gap) that is properly trapped and vented, and that such drains accomplish the objectives and intent of this section.

1010.2.3 Interceptor traps which are connected with the sewer system shall not be near any edible products department or in any area where products are unloaded from or loaded into vehicles. To facilitate cleaning, such traps shall have inclined bottoms and be provided with suitable covers.

1010.3 Collection Centers and Facilities. [AGR] All drains shall be properly installed with adequate deep-sealed traps of the conventional “P,” “U” or “S” type and vents.

1010.4 Horse Meat and Pet Food Establishments.

[AGR] There shall be an efficient drainage and plumbing system for the establishment and premises. All drains and gut- ters shall be installed with traps and vents approved by the Department.

1010.5 Draining and Plumbing. [AGR] There shall be an efficient drainage and plumbing system for the plant and premises.

1010.5.1 Drainage and Gutters. All drains and gut- ters shall be properly installed with approved traps and vents. The drainage and plumbing system must permit the quick runoff of all water from plant buildings, and of surface water around the plant on the premises, and all such water shall be disposed of in such a manner as to prevent a nuisance or health hazard.

1010.5.2 Sewage and Plant Waste. The sewer sys- tem have adequate slope and capacity to remove readily all waste from the various processing operations and to minimize, or if possible, prevent stoppage and surcharg- ing of the system. When the sewage disposal system is a private system which is required to be approved by a state or local health authority, the applicant shall fur- nish the administrator a letter from the proper health authority indicating that the sewage disposal system is acceptable to such authority.

1011.0 Minimum Requirements for Auto Wash Racks.

1011.1 General. A private or public wash rack or floor or slab used for cleaning machinery or machine parts shall be adequately protected against storm or surface water and shall drain or discharge into an approved interceptor (clarifier).

1012.0 Commercial and Industrial Laundries.

1012.1 General. Laundry equipment in commercial and industrial buildings that do not have integral strainers shall discharge into an interceptor having a wire basket or similar device that is removable for cleaning and that will prevent passage into the drainage system of solids [1] ⁄ 2 of an inch (12.7 mm) or larger in maximum dimensions, such as string, rags, buttons, or other solid materials detrimental to the public sewerage system.

1013.0 Bottling Establishments.

1013.1 General. Bottling plants shall discharge their process wastes into an interceptor that will provide for the separation of broken glass or other solids, before discharging liquid wastes into the drainage system.

1014.0 Grease Interceptors.
CPC § 25.4 High relevance — show source text
For SI units: 1 inch = 25.4 mm

Notes: 1 Maintain 1 ⁄ 4 inch per foot slope (20.8 mm/m). 2 The developed length between the trap of a water closet or similar fixture (measured from the face of the closet flange to the inner edge of the vent) and its vent shall not exceed 6 feet (1829 mm). 3 Horizontally wet vented bathtubs, showers and similar fixtures shall be limited to a maximum of 6 feet (1829 mm) for 1½ inch (40 mm) fixture drains and 8 feet (2438 mm) for 2 inch (50 mm) fixture drains, maintaining ¼ inch per foot slope (20.8 mm/m).

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TRAPS AND INTERCEPTORS

1004.0 Traps.

1004.1 Prohibited. No form of trap that depends for its seal upon the action of movable parts shall be used. No trap that has concealed interior partitions, except those of plastic, glass, or similar corrosion-resisting material, shall be used. “S” traps, bell traps, and crown-vented traps shall be prohibited. No fixture shall be double trapped. Drum and bottle traps shall be installed for special conditions. No trap shall be installed without a vent, except as otherwise provided in this code.

1004.2 Movable Parts. Bladders, check valves or another type of devices with moveable parts shall be prohibited to serve as a trap.

1005.0 Trap Seals. 1005.1 General. Each fixture trap shall have a liquid seal of not less than 2 inches (51 mm) and not more than 4 inches (102 mm), except where a deeper seal is found necessary by the Authority Having Jurisdiction. Traps shall be set true with respect to their liquid seals and, where necessary, they shall be protected from freezing.

1006.0 Floor Drain Traps. 1006.1 General. Floor drains shall connect into a trap so constructed that it can be readily cleaned and of a size to serve efficiently the purpose for which it is intended. The drain inlet shall be so located that it is in full view. Where subject to the reverse flow of sewage or liquid waste, such drains shall be equipped with an approved backwater valve.

1007.0 Trap Seal Protection. 1007.1 General. Floor drain or similar traps directly connected to the drainage system and subject to infrequent use shall be protected with a trap seal primer, except where not deemed necessary for safety or sanitation by the Authority Having Jurisdiction. Trap seal primers shall be accessible for maintenance.

1007.2 Trap Seal Primers. Potable water supply trap seal primer valves shall comply with ASSE 1018. Drainage or electronic design type trap seal primer devices shall comply with ASSE 1044 or IAPMO PS 76.
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

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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 § 1010.0 High relevance — show source text
1010.0 Slaughterhouses, Packing Establishments, etc.

1010.1 General. A fish, fowl, and animal slaughterhouse or establishment; a fish, fowl, and meat packing or curing establishment; a soap factory, tallow-rendering, fat-rendering, and a hide-curing establishment shall be connected to and shall drain or discharge into an approved grease interceptor (clarifier).

TABLE 1009.1 APPROVED INTERCEPTORS (CLARIFIERS)

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TRAPS AND INTERCEPTORS

1010.2 Meat and Poultry Processing Plants. [AGR]

1010.2.1 Drainage and Plumbing Systems. Drainage and plumbing systems shall meet the require- ments of Section 724.0.

1010.2.1.1 Each floor drain shall be equipped with a deep-seal trap.

1010.2.2 The plumbing shall be installed so as to prevent sewage from backing up and flooding the floor.

Exception: Floor drains in areas not regularly washed down will be acceptable with deep-seal traps, provided that such drains are connected to secondary drainage systems discharging into a safe sink or basin (air gap) that is properly trapped and vented, and that such drains accomplish the objectives and intent of this section.

1010.2.3 Interceptor traps which are connected with the sewer system shall not be near any edible products department or in any area where products are unloaded from or loaded into vehicles. To facilitate cleaning, such traps shall have inclined bottoms and be provided with suitable covers.

1010.3 Collection Centers and Facilities. [AGR] All drains shall be properly installed with adequate deep-sealed traps of the conventional “P,” “U” or “S” type and vents.

1010.4 Horse Meat and Pet Food Establishments.

[AGR] There shall be an efficient drainage and plumbing system for the establishment and premises. All drains and gut- ters shall be installed with traps and vents approved by the Department.

1010.5 Draining and Plumbing. [AGR] There shall be an efficient drainage and plumbing system for the plant and premises.

1010.5.1 Drainage and Gutters. All drains and gut- ters shall be properly installed with approved traps and vents. The drainage and plumbing system must permit the quick runoff of all water from plant buildings, and of surface water around the plant on the premises, and all such water shall be disposed of in such a manner as to prevent a nuisance or health hazard.
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 § 1003.2 High relevance — show source text
1003.2 Slip Joint Fittings . . . . . . . . . . . . .195

1003.3 Size . . . . . . . . . . . . . . . . . . . . . . . .195

1004.0 Traps . . . . . . . . . . . . . . . . . . . . . .196

1004.1 Prohibited . . . . . . . . . . . . . . . . . . .196

1004.2 Movable Parts . . . . . . . . . . . . . . . .196

1005.0 Trap Seals . . . . . . . . . . . . . . . . . .196

1005.1 General . . . . . . . . . . . . . . . . . . . . .196

1006.0 Floor Drain Traps . . . . . . . . . . . . .196

1006.1 General . . . . . . . . . . . . . . . . . . . . .196

1007.0 Trap Seal Protection . . . . . . . . . . .196

1007.1 General . . . . . . . . . . . . . . . . . . . . .196

1007.2 Trap Seal Primers . . . . . . . . . . . .196

1008.0 Building Traps . . . . . . . . . . . . . . . .196

1008.1 General . . . . . . . . . . . . . . . . . . . . .196

1009.0 Interceptors (Clarifiers) and Separators . . . . . . . . . . . . . . . . . .196

1009.1 Where Required . . . . . . . . . . . . . .196

Table 1009.1 Approved Interceptors (Clarifiers) . .196

1009.2 Approval . . . . . . . . . . . . . . . . . . . .196

1009.3 Design . . . . . . . . . . . . . . . . . . . . .196

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TABLE OF CONTENTS

1009.4 Relief Vent . . . . . . . . . . . . . . . . . .196

1009.5 Location . . . . . . . . . . . . . . . . . . . .196

1009.6 Maintenance of Interceptors . . . . .196

1009.7 Discharge . . . . . . . . . . . . . . . . . . .196

1010.0 Slaughterhouses, Packing Establishments, etc . . . . . . . . . . .196

1010.1 General . . . . . . . . . . . . . . . . . . . . .196

1010.2 Meat and Poultry Processing Plants . . . . . . . . . . . . . . . . . . . . . .197

1010.3 Collection Centers and

Facilities . . . . . . . . . . . . . . . . . . . .197

1010.4 Horse Meat and Pet Food
CPC § 418.0 High relevance — show source text
418.0 Floor Drains.

418.1 Application. Floor drains shall comply with ASME A112.3.1, ASME A112.6.3, or CSA B79.

418.2 Strainer. Floor drains shall be considered plumbing fixtures and each such drain shall be provided with an approved-type strainer having a waterway equivalent to the area of the tailpiece. Floor drains shall be of an approved type and shall provide a watertight joint on the floor.

66 2025 CALIFORNIA PLUMBING CODE

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

PLUMBING FIXTURES AND FIXTURE FITTINGS

418.3 Location of Floor Drains. Floor drains shall be installed in the following areas: (1) Toilet rooms containing two or more water closets or a combination of one water closet and one urinal, except in a dwelling unit. (2) Commercial kitchens and in accordance with Section 704.3.

(3) Laundry rooms in commercial buildings and common laundry facilities in multi-family dwelling buildings. (4) Boiler rooms. 418.4 Food Storage Areas. Where drains are provided in storerooms, walk-in freezers, walk-in coolers, refrigerated equipment, or other locations where food is stored, such drains shall have indirect waste piping. Separate waste pipes shall be run from each food storage area, each with an indirect connection to the building sanitary drainage system. Traps shall be provided in accordance with Section 801.3.2 of this code and shall be vented.

Indirect drains shall be permitted to be located in freezers or other spaces where freezing temperatures are maintained, provided that traps, where supplied, shall be located where the seal will not freeze. Otherwise, the floor of the freezer shall be sloped to a floor drain located outside of the storage compartment. 418.5 Floor Slope. Floors shall be sloped to floor drains.

419.0 Food Waste Disposers. 419.1 Application. Food waste disposal units shall comply with UL 430. Residential food waste disposers shall also comply with ASSE 1008. 419.2 Drainage Connection. Approved wye or other directional-type branch fittings shall be installed in continuous wastes connecting or receiving the discharge from a food waste disposer. No dishwasher drain shall be connected to a sink tailpiece, continuous waste, or trap on the discharge side of a food waste disposer. 419.3 Water Supply. A cold water supply shall be provided for food waste disposers. Such connection to the water supply shall be protected by an air gap or backflow prevention device in accordance with Section 603.2.

420.0 Sinks.
CPC § 417.6 Medium relevance — show source text
Faucets and diverters shall be connected to the water distribution system so that hot water corresponds to the left side of the fixture fitting.

Single-handle mixing valves installed in showers and tub-shower combinations shall have the flow of hot water corresponding to the markings on the fixture fitting. 417.6 Low-Pressure Water Dispenser. Beverage faucets shall comply with ASME A112.18.1/CSA B125.1. Electrically heated or cooled water dispensers shall comply with ASSE 1023.

417.7 Head Shampoo Sink Faucets. Head shampoo sink faucets shall be supplied with hot water that is limited to not more than 120°F (49°C). Each faucet shall have integral check valves to prevent crossover flow between the hot and cold water supply connections. The means for regulating the maximum temperature shall be in accordance with one of the following:

(1) A limiting device conforming to ASSE 1070/ASME A112.1070/CSA B125.70.

(2) A water heater conforming to ASSE 1084.

(3) A temperature-actuated, flow-reduction device conforming to ASSE 1062. 417.8 Footbaths and Pedicure Baths. The water supplied to specialty plumbing fixtures, such as pedicure chairs having an integral foot bathtub and footbaths, shall be limited to not more than 120ºF (49ºC) by a water-temperaturelimiting device that conforms to ASSE 1070/ASME A112.1070/CSA B125.70 or by a water heater complying with ASSE 1084.

418.0 Floor Drains.

418.1 Application. Floor drains shall comply with ASME A112.3.1, ASME A112.6.3, or CSA B79.

418.2 Strainer. Floor drains shall be considered plumbing fixtures and each such drain shall be provided with an approved-type strainer having a waterway equivalent to the area of the tailpiece. Floor drains shall be of an approved type and shall provide a watertight joint on the floor.

66 2025 CALIFORNIA PLUMBING CODE

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

PLUMBING FIXTURES AND FIXTURE FITTINGS

418.3 Location of Floor Drains. Floor drains shall be installed in the following areas: (1) Toilet rooms containing two or more water closets or a combination of one water closet and one urinal, except in a dwelling unit. (2) Commercial kitchens and in accordance with Section 704.3.

(3) Laundry rooms in commercial buildings and common laundry facilities in multi-family dwelling buildings. (4) Boiler rooms. 418.4 Food Storage Areas. Where drains are provided in storerooms, walk-in freezers, walk-in coolers, refrigerated equipment, or other locations where food is stored, such drains shall have indirect waste piping. Separate waste pipes shall be run from each food storage area, each with an indirect connection to the building sanitary drainage system. Traps shall be provided in accordance with Section 801.3.2 of this code and shall be vented.
CPC § 908.2.4 Medium relevance — show source text
908.2.4 Water Closet. The water closet fixture drain or trap arm connection to the wet vent shall be downstream of fixture drain or trap arm connections to the horizontal wet vent.

908.2.5 Additional Fixtures. Additional fixtures shall discharge downstream of the wet vent system and be conventionally vented. Only the fixtures within the bathroom group shall connect to the wet-vented horizontal branch.

909.0 Special Venting for Island Fixtures. 909.1 General. Traps for island sinks and similar equipment shall be roughed in above the floor and shall be permitted to be vented by extending the vent as high as possible, but not less than the drainboard height and then returning it downward and connecting it to the horizontal sink drain immediately downstream from the vertical fixture drain. The return vent shall be connected to the horizontal drain through a wyebranch fitting and shall, in addition, be provided with a foot vent taken off the vertical fixture vent by means of a wye branch immediately below the floor and extending to the nearest partition and then through the roof to the open air, or shall be permitted to be connected to other vents at a point not less than 6 inches (152 mm) above the flood-level rim of the fixtures served. Drainage fittings shall be used on the vent below the floor level, and a slope of not less than [1] ⁄ 4 inch per foot (20.8 mm/m) back to the drain shall be maintained. The return bend used under the drainboard shall be a one-piece

fitting or an assembly of a 45 degree (0.79 rad), a 90 degree (1.57 rad), and a 45 degree (0.79 rad) elbow in the order named. Pipe sizing shall be as elsewhere required in this code. The island sink drain, upstream of the returned vent, shall serve no other fixtures. An accessible cleanout shall be installed in the vertical portion of the foot vent.

910.0 Combination Waste and Vent Systems. 910.1 Where Permitted. Combination waste and vent systems shall be permitted where structural conditions preclude the installation of conventional systems as otherwise prescribed by this code. 910.2 Approval. Construction documents for each combination waste and vent system shall first be approved by the Authority Having Jurisdiction before a portion of such system is installed.

910.3 Vents. Each combination waste and vent system, as defined in Chapter 2, shall be provided with a vent or vents adequate to ensure free circulation of air. A branch exceeding 15 feet (4572 mm) in length shall be separately vented in an approved manner. The area of a vent installed in a combination waste and vent system shall be not less than one-half the inside cross-sectional area of the drainpipe served. The vent connection shall be downstream of the uppermost fixture. 910.4 Connections and Size. Branches serving traps shall connect to the main line at an angle not exceeding 2 percent. Each waste pipe and each trap in such a system shall be not less than two pipe sizes exceeding the sizes required by Chapter 7 of this code, and not less than two pipe sizes exceeding a fixture tailpiece or connection. 910.5 Vertical Waste Pipe. No vertical waste pipe shall be used in such a system, except the tailpiece or connection between the outlet of a plumbing fixture and the trap. Such tailpieces or connections shall be as short as possible, and in no case shall exceed 2 feet (610 mm).

Frequently asked questions

Can I install a building trap whenever I want?

No — building traps are prohibited unless required by the Authority Having Jurisdiction (AHJ). If the AHJ requires one, it must have an accessible cleanout and a relieving vent/fresh‑air intake per § 1008.1 .

When does a floor drain need a backwater valve?

If the floor drain is subject to reverse flow of sewage or liquid waste, the drain must be equipped with an approved backwater valve per § 1006.1 .

Do I have to protect rarely used floor drains from evaporation?

Yes — floor drains and similar traps that are directly connected and subject to infrequent use should be protected with a trap seal primer unless the AHJ determines it’s unnecessary; primers must be accessible for maintenance (§ 1007.1–1007.2) .

What size can the relieving vent (fresh‑air intake) for a building trap be?

The code limits that relieving vent or fresh‑air intake to no larger than one‑half the diameter of the drain to which it connects, and it must be carried above grade to a screened outlet outside the building (§ 1008.1) .

Does the drain inlet have to be visible?

Yes — § 1006.1 requires the drain inlet be so located that it is in full view, to facilitate inspection and maintenance .

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California Plumbing Code