CPC · California Plumbing Code

Maximum unit loading and maximum length limits for drainage and vent piping

Q: How do I find the numeric DFU and length limits for a 3‑inch stack?

Look up Table 703.2 and read the column for 3‑inch pipe to get both the maximum DFU (vertical/horizontal) and the maximum developed‑length allowed for that size; the controlling entry and the explanatory notes are referenced by § 703.2 .

Q: If I upsize a vent by one pipe size, do I still need to respect the table’s length limit?

If you increase a minimum‑sized vent one pipe size for its entire length , the table’s maximum length limits do not apply to that vent per § 904.2 — but you still must size the vent for the total DFU and observe the minimum diameter rules.

Q: Are trap arms counted toward the maximum DFU for a vertical stack?

Table 703.2 normally lists drainage DFU excluding the trap arm where noted; always read the table notes and Chapter 10 trap/trap‑arm tables for the correct counting method.

Q: What is the effect of reduced slope on horizontal fixture‑unit capacity?

Table 703.2 assumes 1/4 in./ft slope; if the slope is reduced to 1/8 in./ft , multiply horizontal fixture‑unit capacity by the factor listed in the table notes (see Table 703.2 notes).

Q: Where do wet‑vent limits appear?

Wet‑vent developed‑length and sizing limits are in § 908.0 et seq.; for example, § 908.1 limits many wet‑vent lengths to 6 ft and prescribes required upsizing where applicable.

Table 703.2 and § 703.2 of the California Plumbing Code set the maximum fixture‑unit loads and developed‑length limits for drainage and vent piping; vents must be at least 1‑1/4 in. (and at least half the drain diameter), no more than one‑third of a minimum vent’s allowed length may be horizontal, and many wet‑vent and trap‑arm rules (for example, 6‑ft limits) further restrict layout — always consult Table 703.2 and the cited sections when sizing.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

The maximum number of connected fixture units and the maximum developed lengths for drainage and vent piping are set by Table 703.2 and the sizing rules in § 703.2 of the California Plumbing Code. Vents are sized by the total fixture-unit load and the vent’s developed length (not less than 1-1/4 in. and not less than one-half the diameter of the drain it serves) and have a limit on how much of that length can be horizontal per § 904.1 and § 904.2. Special wet‑vent length limits (for example, 6 ft for many wet vents) and trap‑arm developed‑length limits are given elsewhere in Chapter 7 and Chapter 10 and are explicitly cross‑referenced by Table 703.2 and the related sections. See § 703.2 and Table 703.2 for the numeric limits and specific pipe‑size capacities.

The single most important rule: use Table 703.2 to read the maximum fixture‑unit load and the maximum developed length allowed for a given pipe diameter; then size vents by the total fixture units and developed length rules in § 904.1–904.2.

Requirements in detail

What Table 703.2 controls

Table 703.2 gives the maximum fixture‑unit loading (DFU) permitted on drainage piping (vertical and horizontal) and on vent piping, and it gives maximum developed lengths for vertical drainage pipes and vents. Consult Table 703.2 for the exact numeric DFU limits and length limits by nominal pipe diameter. § 703.2 describes the table’s purpose and application.

Vent sizing and developed length (key rules)

The size of vent piping is determined from the vent’s developed length and total DFU connected to it in accordance with Table 703.2 — minimum individual vent diameter is 1-1/4 in., and a vent must be at least one‑half the diameter of the drain to which it connects (§ 904.1).
Not more than one‑third of the total permitted developed length of a minimum‑sized vent may be installed horizontally. If the vent is upsized one pipe size for its entire length, the table’s maximum length limits do not apply to that vent (see § 904.2).

Wet vents and trap arms (limits that affect Table 703.2 application)

Vertical wet vents are limited in developed length (no wet vent shall exceed 6 ft in developed length for the common wet‑vent application described) and have sizing rules that may require upsizing; see § 908.1.
Trap‑arm developed lengths and fixture‑to‑vent distances (for example, the 6 ft developed length limit for water closets and similar fixtures) are set in Chapter 10 tables and notes and must be observed when computing the DFU loading on a branch or vent. (See Table 1002.2 notes and related text.)

Decision‑relevant quick reference table

Topic	Key value / threshold	Code reference
Minimum individual vent diameter	1‑1/4 in. (and not less than one‑half the diameter of served drain)	§ 904.1
Maximum horizontal portion of a minimum‑sized vent	≤ 1/3 of total permitted developed length; upsizing vent removes length limit	§ 904.2
Wet‑vent developed length limit	6 ft (common vertical or horizontal wet‑vent limit per § 908.1)	§ 908.1
Trap to vent developed length (water closet and similar)	6 ft (see trap/arm rules and Table 1002.2 note)	Table 1002.2 note / Chapter 10
Maximum DFU and developed lengths by pipe diameter	See Table 703.2 — pipe‑size specific numeric limits for drainage and vent piping	§ 703.2 and Table 703.2

Notes in Table 703.2 (decision points):

The table’s listed drainage fixture units typically exclude the trap arm when counting load for the drain column (see Table notes).
Table notes cover slope assumptions (standard 1/4 in./ft) and provide multipliers if slope is reduced.

Exceptions & special cases

If a minimum‑sized vent is increased one pipe size for its entire length, the maximum developed‑length limitations in Table 703.2 do not apply to that vent (see § 904.2).
Wet venting is restricted to specific fixture groups and limits; wet vents also have special sizing and developed‑length rules in § 908.0 et seq. — do not use Table 703.2 alone for wet‑vent design without checking § 908.1 and related subsections.
Trap and trap‑arm limits (Table 1002.2 and Table 702.1(1)) may further limit how many fixtures can practically be served even if Table 703.2 would allow more DFU on the receiving stack; always reconcile trap‑arm/fixture rules with Table 703.2.

Common mistakes

Relying on Table 703.2 for vent sizing without applying the vent developed‑length rules in § 904.2 (especially the “one‑third horizontal” rule).
Forgetting the minimum vent diameter requirement (1-1/4 in.) and the rule that a vent can’t be smaller than half the diameter of the drain it serves (§ 904.1).
Using the total DFU from Table 702.1 without subtracting the trap arm where Table 703.2 notes require exclusion of the trap arm from the drain load count.
Missing slope adjustments: Table 703.2 (and its notes) assume 1/4 in./ft slope; reduced slope requires multiplying horizontal DFUs by the factor provided in the table notes.

Worked example — concrete scenario

Situation: You have a branch vent that serves a group of lavatories and a shower. The total calculated fixture‑unit load (per Table 702.1 and 702.2) is 6 DFU, and the vent developed length from the most remote fixture to the vent termination (measured along the vent path) is 48 ft. You plan to run a 1‑1/4 in. vent.

Steps:

Check minimum vent size: 1‑1/4 in. is the minimum permitted but must also be sized for the DFU and developed length per Table 703.2 and § 904.1.
Consult Table 703.2: find the maximum DFU allowed on a 1‑1/4 in. vent and the maximum developed length for that size. If Table 703.2 shows that a 1‑1/4 in. vent is limited to 1 DFU and 45 ft developed length (example — consult the table for the actual numeric entries), then your planned 6 DFU / 48 ft run exceeds the limit for a 1‑1/4 in. vent.
Options: (a) increase the vent to the next size and re‑check Table 703.2 for allowed DFU and developed length values; or (b) reduce the vent’s developed length (e.g., provide a vent closer to the fixtures). Note also per § 904.2 that if you increase the vent one pipe size for its entire length, the table’s length limit may not apply (verify the table and local AHJ practice).

Conclusion for the example: do not use a 1‑1/4 in. vent in this scenario — select the next larger size that, per Table 703.2, can carry 6 DFU over 48 ft or else shorten the developed length. Always confirm the numeric entries in Table 703.2 for the selected pipe size.

Related provisions

§ 703.1 — Minimum sizes and how length affects vertical drainage sizing.
§ 704.0 – 704.3 — Fixture connection rules that affect how fixture loads are counted.
§ 904.1 – 904.2 — Vent sizing and the horizontal‑length limitation for minimum‑sized vents.
§ 908.0 – 908.2 — Wet‑venting specifics and developed‑length limits (6 ft limit).
Table 1002.2 and its notes — Trap‑arm developed‑length limits (water closets and similar fixtures).

Code references

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

CPC § 702.2 High relevance — show source text
Table 702.2 Discharge Capacity in Gallons Per Minute for

Intermittent Flow Only . . . . . . . . .168

702.3 Continuous Flow . . . . . . . . . . . . . .168

703.0 Size of Drainage Piping . . . . . . . .168

703.1 Minimum Size . . . . . . . . . . . . . . . .168

703.2 Maximum Number of Fixture

Units . . . . . . . . . . . . . . . . . . . . . . .168

703.3 Sizing per Appendix C . . . . . . . . .168

704.0 Fixture Connections (Drainage) . .168

704.1 Inlet Fittings . . . . . . . . . . . . . . . . .168

704.2 Single Vertical Drainage Pipe . . . .168

704.3 Commercial Sinks . . . . . . . . . . . . .168

Table 703.2 Maximum Unit Loading and Maximum Length of Drainage and Vent Piping . . . . . . . . . . . . . .169

705.0 Joints and Connections . . . . . . . .169

705.1 ABS and ABS Co-Extruded

Plastic Pipe and Joints . . . . . . . . .169

705.2 Cast-Iron Pipe and Joints . . . . . . .169

705.3 Copper or Copper Alloy Pipe (DWV) and Joints . . . . . . . . .170

705.4 Galvanized Steel Pipe and Joints . . . . . . . . . . . . . . . . . . .170

705.5 Polyethylene (PE) Sewer Pipe . . .170

xxxiv 2025 CALIFORNIA PLUMBING CODE

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TABLE OF CONTENTS

705.6 PVC and PVC Co-Extruded

Plastic Pipe and Joining Methods . . . . . . . . . . . . . . . . . . . .171

705.7 Stainless Steel Pipe and Joints . . .171

705.8 Vitrified Clay Pipe and Joints . . . .171

705.9 Special Joints . . . . . . . . . . . . . . . .171

705.10 Joints Between

Various Materials . . . . . . . . . . . . .171

706.0 Changes in Direction of Drainage Flow . . . . . . . . . . . . . . .172

706.1 Approved Fittings . . . . . . . . . . . . .172

706.2 Horizontal to Vertical . . . . . . . . . .172

706.3 Horizontal to Horizontal . . . . . . . .172

706.4 Vertical to Horizontal . . . . . . . . . .172

707.0 Cleanouts . . . . . . . . . . . . . . . . . . .172

707.1 Plug . . . . . . . . . . . . . . . . . . . . . . .172

Table 707.1 Cleanouts . . . . . . . . . . . . . . . . . . .172

707.2 Approved . . . . . . . . . . . . . . . . . . .172

CPC § 704.0 High relevance — show source text

704.0 Fixture Connections (Drainage). 704.1 Inlet Fittings. Drainage piping shall be provided with approved inlet fittings for fixture connections, correctly located according to the size and type of fixture proposed to be connected.

704.2 Single Vertical Drainage Pipe. Two fixtures set back-to-back, or side-by-side, within the distance allowed between a trap and its vent, shall be permitted to be served by a single vertical drainage pipe provided that each fixture wastes separately into an approved double-fixture fitting having inlet openings at the same level. 704.3 Commercial Sinks. Pot sinks, scullery sinks, dishwashing sinks, silverware sinks, and other similar fixtures shall be connected directly to the drainage system. A floor drain shall be provided adjacent to the fixture and shall be connected on the sewer side of the sink. No other drainage

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SANITARY DRAINAGE

TABLE 703.2

MAXIMUM UNIT LOADING AND MAXIMUM LENGTH OF DRAINAGE AND VENT PIPING

SIZE OF PIPE (inches)	11⁄4	11⁄2	2	3	4	5	6	8	10	12
Maximum Units Drainage Piping1 Vertical Horizontal	1 1	22, 7 17	163 83	484 354	256 2165	600 4285	1380 7205	3600 26405	5600 46805	8400 82005
Maximum Length Drainage Piping Vertical, (feet) Horizontal (unlimited)	45	65	85	212	300	390	510	750	–	–
Vent Piping Horizontal and Vertical6 Maximum Units Maximum Lengths, (feet)	1 45	83 60	24 120	84 212	256 300	600 390	1380 510	3600 750	–	–

For SI units: 1 inch = 25 mm, 1 foot = 304.8 mm

Notes: 1 Excluding trap arm. 2 Except for sinks, urinals, and dishwashers – exceeding 1 fixture unit. 3 Except for six-unit traps or water closets.

CPC § 811.0. High relevance — show source text
defined in Section 811.0.

903.2.3 Marking. Copper or copper alloy tubing, in addition to the required incised marking, shall be marked in accordance with either ASTM B306 or ASTM B88. The colors shall be Type K, green; Type L, blue; Type M, red; and Type DWV, yellow. 903.3 Changes in Direction. Changes in the direction of vent piping shall be made by the appropriate use of approved fittings, and no such pipe shall be strained or bent. Burred ends shall be reamed to the full bore of the pipe.

904.0 Size of Vents.

904.1 Size. The size of vent piping shall be determined from its length and the total number of fixture units connected thereto, in accordance with Table 703.2. The diameter of an individual vent shall be not less than 1 [1] ⁄ 4 inches (32 mm) nor less than one-half the diameter of the drain to which it is connected. In addition, the drainage piping of each building and each connection to a public sewer or a private sewage disposal system shall be vented by means of one or more vent pipes, the aggregate cross-sectional area of which shall be not less than that of the largest required building sewer as determined from Table 703.2. Vent pipes from fixtures located upstream from pumps, ejectors, backwater valves, or other devices that obstruct the free flow of air and other gases between the building sewer and the outside atmosphere shall not be used for meeting the cross-sectional area venting requirements of this section. Exception: Where connected to a common building sewer, the drainage piping of two or more buildings located on the same lot and under one ownership shall be permitted to be vented by means of piping sized in accordance with Table 703.2, provided the aggregate cross-sectional area of vents is not less than that of the largest required common building sewer. 904.2 Length. Not more than one-third of the total permitted length, in accordance with Table 703.2, of a minimumsized vent shall be installed in a horizontal position. Where a minimum-sized vent is increased one pipe size for its entire length, the maximum length limitation shall not apply.

2025 CALIFORNIA PLUMBING CODE 189

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VENTS

905.0 Vent Pipe Grades and Connections. 905.1 Grade. Vent and branch vent pipes shall be free from drops or sags, and each such vent shall be level or shall be so graded and connected as to drip back by gravity to the drainage pipe it serves. 905.2 Horizontal Drainage Pipe. Where vents connect to a horizontal drainage pipe, each vent pipe shall have its invert taken off above the drainage centerline of such pipe downstream of the trap being served. 905.3 Vent Pipe Rise. Unless prohibited by structural conditions, each vent shall rise vertically to a point not less than 6 inches (152 mm) above the flood-level rim of the fixture served before offsetting horizontally, and where two or more vent pipes converge, each such vent pipe shall rise to a point not less than 6 inches (152 mm) in height above the floodlevel rim of the plumbing fixture it serves before being connected to any other vent. Vents less than 6 inches (152 mm) above the flood-level rim of the fixture shall be installed with approved drainage fittings, material, and grade to the drain.
CPC § 701.0 High relevance — show source text
701.0 General . . . . . . . . . . . . . . . . . . . . .165

701.1 Applicability . . . . . . . . . . . . . . . . . .165

701.2 Drainage Piping . . . . . . . . . . . . . .165

701.3 Drainage Fittings . . . . . . . . . . . . .165

701.4 Continuous Wastes . . . . . . . . . . .165

701.5 Lead . . . . . . . . . . . . . . . . . . . . . . .165

701.6 Caulking Ferrules . . . . . . . . . . . . .165

701.7 Soldering Bushings . . . . . . . . . . . .165

Table 701.6 Caulking Ferrules . . . . . . . . . . . . .165

Table 701.7 Soldering Bushings . . . . . . . . . . . .165

702.0 Fixture Unit Equivalents . . . . . . . .165

702.1 Trap Size . . . . . . . . . . . . . . . . . . .165

Table 701.2 Materials for Drain, Waste, Vent Pipe and Fittings . . . . . . . . .166

Table 702.1 Drainage Fixture Unit Values (DFU) . . . . . . . . . . . . . . . .167

Table 702.1(1) Maximum Drainage Fixture Units for a Trap and Trap Arm . . .168

702.2 Intermittent Flow . . . . . . . . . . . . . .168

Table 702.2 Discharge Capacity in Gallons Per Minute for

Intermittent Flow Only . . . . . . . . .168

702.3 Continuous Flow . . . . . . . . . . . . . .168

703.0 Size of Drainage Piping . . . . . . . .168

703.1 Minimum Size . . . . . . . . . . . . . . . .168

703.2 Maximum Number of Fixture

Units . . . . . . . . . . . . . . . . . . . . . . .168

703.3 Sizing per Appendix C . . . . . . . . .168

704.0 Fixture Connections (Drainage) . .168

704.1 Inlet Fittings . . . . . . . . . . . . . . . . .168

704.2 Single Vertical Drainage Pipe . . . .168

704.3 Commercial Sinks . . . . . . . . . . . . .168

Table 703.2 Maximum Unit Loading and Maximum Length of Drainage and Vent Piping . . . . . . . . . . . . . .169

705.0 Joints and Connections . . . . . . . .169

705.1 ABS and ABS Co-Extruded

Plastic Pipe and Joints . . . . . . . . .169

705.2 Cast-Iron Pipe and Joints . . . . . . .169

705.3 Copper or Copper Alloy Pipe (DWV) and Joints . . . . . . . . .170

705.4 Galvanized Steel Pipe and Joints . . . . . . . . . . . . . . . . . . .170

705.5 Polyethylene (PE) Sewer Pipe . . .170
CPC § 304.8 High relevance — show source text
(feet)
Horizontal (unlimited)|

45|

65|

85|

212|

300|

390|

510|

750|

–|

–| |Vent Piping
Horizontal and Vertical6
Maximum Units
Maximum Lengths, (feet)|

1
45|

83
60|

24
120|

84
212|

256
300|

600
390|

1380
510|

3600
750|

–|

–|

For SI units: 1 inch = 25 mm, 1 foot = 304.8 mm

Notes: 1 Excluding trap arm. 2 Except for sinks, urinals, and dishwashers – exceeding 1 fixture unit. 3 Except for six-unit traps or water closets. 4 Not to exceed six water closets or five six-unit traps. 5 Based on 1 ⁄ 4 inch per foot (20.8 mm/m) slope. For 1 ⁄ 8 of an inch per foot (10.4 mm/m) slope, multiply horizontal fixture units by a factor of 0.8. 6 The diameter of an individual vent shall be not less than 1 1 ⁄ 4 inches (32 mm) nor less than one-half the diameter of the drain to which it is connected. Fixture unit load values for drainage and vent piping shall be computed from Table 702.1 and Table 702.2. Not to exceed one-third of the total permitted length of a vent shall be permitted to be installed in a horizontal position. Where vents are increased one pipe size for their entire length, the maximum length limitations specified in this table do not apply. This table is in accordance with the requirements of Section 901.3. 7 Up to 8 public lavatories are permitted to be installed on a 1 1 ⁄ 2 inch (40 mm) vertical branch or horizontal sanitary branch sloped at 1 ⁄ 4 inch per foot (20.8 mm/m).

line shall be connected between the floor drain waste con nection and the fixture drain. The fixture and floor drain shall be trapped and vented in accordance with this code.

705.0 Joints and Connections.

705.1 ABS and ABS Co-Extruded Plastic Pipe and Joints. Joining methods for ABS plastic pipe and fittings shall be installed in accordance with the manufacturer’s installation instructions and shall comply with Section 705.1.1 through Section 705.1.3. 705.1.1 Mechanical Joints. Mechanical joints shall be designed to provide a permanent seal and shall be of the mechanical or push-on joint. The push-on joint shall include an elastomeric gasket that complies with ASTM D3212 and shall provide a compressive force against the spigot and socket after assembly to provide a permanent seal.

CPC § 0.06 High relevance — show source text

INTERMITTENT FLOW ONLY*

GPM	FIXTURE UNITS
Up to 71⁄2	Equals 1 Fixture Unit
Greater than 71⁄2 to 15	Equals 2 Fixture Units
Greater than 15 to 30	Equals 4 Fixture Units
Greater than 30 to 50	Equals 6 Fixture Units

For SI units: 1 gallon per minute = 0.06 L/s

Discharge capacity exceeding 50 gallons per minute (3.15 L/s) shall be determined by the Authority Having Jurisdiction.

702.3 Continuous Flow. For a continuous flow into a drainage system, such as from a pump, sump ejector, air conditioning equipment, or similar device, 2 fixture units shall be equal to each gallon per minute (gpm) (L/s) of flow.

703.0 Size of Drainage Piping. 703.1 Minimum Size. The minimum sizes of vertical, horizontal, or both drainage piping shall be determined from the total of fixture units connected thereto, and additionally, in the case of vertical drainage pipes, in accordance with their length.

703.2 Maximum Number of Fixture Units. Table 703.2

shows the maximum number of fixture units allowed on a vertical or horizontal drainage pipe, building drain, or building sewer of a given size; the maximum number of fixture units allowed on a branch interval of a given size; and the maximum length (in feet and meters) of a vertical drainage pipe of a given size. 703.3 Sizing per Appendix C. For alternate method of sizing drainage piping, see Appendix C.

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TABLE 703.2

MAXIMUM UNIT LOADING AND MAXIMUM LENGTH OF DRAINAGE AND VENT PIPING

SIZE OF PIPE (inches)	11⁄4	11⁄2	2	3	4	5	6	8	10	12
Maximum Units Drainage Piping1 Vertical Horizontal	1 1	22,

CPC § 2.2 High relevance — show source text

For drainage fixture unit values related to lots within special occupancy parks in all parts of the State of Cal-_ ifornia, see California Code of Regulations, Title 25, Division 1, Chapter 2.2, Article 5, Section 2268.

required, and the unit equivalent of fixtures and devices not shown in Table 702.1 shall be based on the size of trap or trap

arm.

Maximum drainage fixture units for a fixture trap and trap arm loadings for sizes up to 4 inches (100 mm) shall be in accordance with Table 702.1(1).

TABLE 702.1(1) MAXIMUM DRAINAGE FIXTURE UNITS FOR A

TRAP AND TRAP ARM*

SIZE OF TRAP AND TRAP ARM (inches)	DRAINAGE FIXTURE UNIT VALUES (DFU)
11⁄4	1 unit
11⁄2	3 units
2	4 units
3	6 units
4	8 units

For SI Units: 1 inch = 25 mm

*** Exception:** On self-service laundries.

702.2 Intermittent Flow. Drainage fixture units for intermittent flow into the drainage system shall be computed on the rated discharge capacity in gallons per minute (gpm) (L/s) in accordance with Table 702.2.

TABLE 702.1(1) MAXIMUM DRAINAGE FIXTURE UNITS FOR A

TRAP AND TRAP ARM*

For SI Units: 1 inch = 25 mm

*** Exception:** On self-service laundries.

TABLE 702.2

DISCHARGE CAPACITY IN GALLONS PER MINUTE FOR

INTERMITTENT FLOW ONLY*

GPM	FIXTURE UNITS
Up to 71⁄2	Equals 1 Fixture Unit
Greater than 71⁄2 to 15	Equals 2 Fixture Units
Greater than 15 to 30	Equals 4 Fixture Units
Greater than 30 to 50	Equals 6 Fixture Units

For SI units: 1 gallon per minute = 0.06 L/s

Discharge capacity exceeding 50 gallons per minute (3.15 L/s) shall be determined by the Authority Having Jurisdiction.

703.2 Maximum Number of Fixture Units. Table 703.2

CPC § 905.4 High relevance — show source text
Undiminished in

size through roof . . . . . . . . . . . . . . . . . . .905.4, 907.1 Unit loading . . . . . . . . . . . . . . . . . . . . . . . . .Table 703.2

Wet, Horizontal . . . . . . . . . . . . . . . . . . . . . . . . . . .908.2

Wet, Vertical . . . . . . . . . . . . . . . . . . . . . . . . . . . . .908.1

Yoke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227.0, 907.0

VENTED APPLIANCE, DEFINITION . . . . . . . . . . . . . .224.0

Category I Vented Appliance, definition . . . . . . . . .224.0 Category II Vented Appliance, definition . . . . . . . .224.0 Category III Vented Appliance, definition . . . . . . . .224.0 Category IV Vented Appliance, definition . . . . . . .224.0 VENTILATING HOODS . . . . . . . . . . . . . . . .509.2.4, 509.3.4

VERTICAL-TO-HORIZONTAL

DRAINAGE FITTINGS . . . . . . . . . . . . . . . . . . . . . . .706.4

VERTICAL WET VENTING . . . . . . . . . . . . .(see Wet vents) VIOLATION, NOTICES OF . . . . . . . . . . . . . . . . . . . . . .106.2

VITRIFIED CLAY PIPE . . . . . . . . .701.2, Table 701.2, 705.8,

811.2, Table 1101.4.6

– W –

WALL, EXTENSION THROUGH . . . . .312.1, 509.6.1, 509.8

WALL-HUNG FIXTURES,

INSTALLATION OF . . . . . . . . . . . . . . . . . . . . .402.4, 402.6

WASH FOUNTAINS . . . . . . . . . . . . . . . . . . . . . 417.1.1, 417.1.2

WASH RACKS, AUTO . . . . . . . . . . . . . . . . . . . . . . . . . 1011.0

WASTES

Anesthetic gas disposal . . . . . . . . . . . . . . . . . . . .1301.2 Chemical . . . . . . . . . . . . . . . . . . . .205.0, 811.0, 903.2.2

Clear water . . . . . . . . . . . . . . . . . . . . . . . . .205.0, 812.0

Condensate . . . . . . . . . . . . . . . . . . . . . . . . .807.2, 814.0
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).

1003.2 Slip Joint Fittings. A maximum of one approved slip joint fitting shall be permitted to be used on the outlet side of a trap, and no tubing trap shall be installed without a listed tubing trap adapter. Listed plastic trap adapters shall be permitted to be used to connect listed metal tubing traps.

1003.3 Size. The size (nominal diameter) of a trap for a given fixture shall be sufficient to drain the fixture rapidly but in no case less than nor more than one pipe size larger than given in Table 702.1. The trap shall be the same size as the trap arm to which it is connected.

TABLE 1002.2

HORIZONTAL LENGTHS OF TRAP ARMS (EXCEPT FOR WATER CLOSETS AND SIMILAR FIXTURES) [1, 2, 3]

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).

2025 CALIFORNIA PLUMBING CODE 195

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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.
California Plumbing Code High relevance — show source text

|1280
|2030
|3590
|7330
| |550
|52
|109
|204
|420
|629
|1210
|1930
|3410
|6960
| |600
|50
|104
|195
|400
|600
|1160
|1840
|3260
|6640
| |650
|47
|99
|187
|384
|575
|1110
|1760
|3120
|6360
| |700
|46
|95
|179
|368
|552
|1060
|1690
|3000
|6110
| |750
|44
|92
|173
|355
|532
|1020
|1630
|2890
|5890
| |800
|42
|89
|167
|343
|514
|989
|1580
|2790
|5680
| |850
|41
|86
|162
|332
|497
|957
|1530
|2700
|5500
| |900
|40
|83
|157
|322
|482
|928
|1480
|2610
|5330
| |950
|39
|81
|152
|312
|468
|901
|1440
|2540
|5180
| |1000<b
CPC § 4.5 High relevance — show source text
0|4.5|4.1|4.1| |Each Additional1⁄2 Bath|0.5|0.1|0.4|0.4| |Each Additional Bathroom Group|1.0|0.5|0.8|0.8| |Other Groups of Fixtures|Other Groups of Fixtures|Other Groups of Fixtures|Other Groups of Fixtures|Other Groups of Fixtures| |Bathroom Group (1.6 GPF Flushometer Value)|6.0|2.5|4.0|1.7| |Kitchen Group (Sink and Dishwasher)|2.0|2.0|1.5|1.5| |Laundry Group (Sink and Clothes Washer)|5.0|5.0|3.0|3.0|

Notes: 1 A bathroom group, for this table, consists of one water closet, up to two lavatories, and either one bathtub or one shower. 2 A half-bath or powder room, for this table, consists of one water closet and one lavatory. 3 Multi-unit dwellings with individual water heaters use the same WSFU as for individual dwellings.

C 304.2 Size of Building Drain and Building Sewer. The maximum number of drainage fixture units allowed on the building drain or building sewer of a given size shall be in accordance with Table C 304.2. The size of a building drain or building sewer serving a water closet shall be not less than 3 inches (80 mm).

C 304.3 Size of Horizontal Branch or Vertical Stack. The maximum number of drainage fixture units allowed on a horizontal branch or vertical soil or waste stack of a given size shall be in accordance with Table C 304.3. Stacks shall

be sized based on the total accumulated connected load at each story or branch interval.

C 304.3.1 Horizontal Stack Offsets. Horizontal

stack offsets shall be sized in accordance with Table C 304.2 as required for building drains.

C 304.3.2 Vertical Stack Offsets. Vertical stack off sets shall be sized in accordance with Table C 304.3 as required for stacks.

C 304.4 Horizontal Stack Offset and Horizontal Branch

Connections. Horizontal branch connections shall not connect to a horizontal stack offset or within 2 feet (610 mm) above or below the offset where such horizontal offset is located more than four branch intervals below the top of the stack.

C 401.0 Vent System Sizing. C 401.1 Size of Vents. The size of vent piping shall be determined from the developed length and the total number of drainage fixture units connected in accordance with Table C 401.1. Vents shall be not less than one-half the required size of the drainage pipe size served as determined by Table C 304.3 for horizontal fixture branches and stacks nor less than 1 [1] ⁄ 4 inches

(32 mm) in diameter. The drainage system shall be vented by not less than one vent pipe which shall be not less than one-half the size of the required building drain and which shall extend from the building drain or extension of building drain to the outdoors. Vents shall be installed in accordance with Chapter 9. C 401.2 Vent Stack. A vent stack shall be required for a drainage stack that extends five or more branch intervals above the building drain or horizontal branch. The developed length of the vent stack shall be measured from the lowest connection of a branch vent to the termination outdoors.

CPC § 601.4.1 High relevance — show source text

Exception: Water closets shall be permitted to be up to 8 feet (2438 mm) horizontally from the stack where connected to the stack through a sanitary tee.

C 601.4.1 Other Fixtures. Fixtures other than water closets shall be not more than 12 feet (3658 mm) horizontally from the stack. C 601.4.2 Length of Vertical Piping. The length of vertical piping from a fixture trap to a horizontal branch shall not be considered in computing the fixture’s horizontal distance from the stack.

C 601.5 Maximum Vertical Drops from Fixtures. Vertical drops from fixture traps to horizontal branch piping shall be one size larger than the trap size, but not less than 2 inches (50 mm) in diameter. Vertical drops shall be 4 feet (1219 mm) maximum length. Fixture drains that are not increased in size, or have a vertical drop exceeding 4 feet (1219 mm) shall be individually vented. C 601.6 Additional Venting Required. Additional venting shall be provided where more than one water closet is on a horizontal branch and where the distance from a fixture trap to the stack exceeds the limits in Section C 601.4. Where additional venting is required, the fixture(s) shall be vented by one of the methods described in Section 908.0 through Section 911.5. The dry vent extensions for the additional venting shall connect to a branch vent, vent stack, stack vent, or be extended outdoors and terminate to the open air.

392 2025 CALIFORNIA PLUMBING CODE

APPENDIX C

TABLE C 601.2 SINGLE STACK SIZE*	Col2	Col3	Col4
MAXIMUM CONNECTED DRAINAGE FIXTURE UNITS	MAXIMUM CONNECTED DRAINAGE FIXTURE UNITS	MAXIMUM CONNECTED DRAINAGE FIXTURE UNITS	MAXIMUM CONNECTED DRAINAGE FIXTURE UNITS
STACK SIZE (inches)	STACKS LESS THAN 75 FEET IN HEIGHT	STACK 75 FEET TO LESS THAN 160 FEET IN HEIGHT	STACK 160 FEET OR GREATER IN HEIGHT
3	24	NP	NP
4	225	24	NP
5	480	225	24
6	1015	480	225
8	2320	1015	480
10	4500	2320	1015
12	8100	4500	2320
15	13 600	8100	4500

For SI units: 1 inch = 25 mm, 1 foot = 304.8 mm

NP = Not permitted

C 601.7 Stack Offsets. Where there are no fixture drain connections below a horizontal offset in a stack, the offset does not need to be vented. Where there are fixture drain connections below a horizontal offset in a stack, the offset shall be vented. There shall be no fixture connections to a stack within 2 feet (610 mm) above and below a horizontal offset.

Frequently asked questions

How do I find the numeric DFU and length limits for a 3‑inch stack?

Look up Table 703.2 and read the column for 3‑inch pipe to get both the maximum DFU (vertical/horizontal) and the maximum developed‑length allowed for that size; the controlling entry and the explanatory notes are referenced by § 703.2.

If I upsize a vent by one pipe size, do I still need to respect the table’s length limit?

If you increase a minimum‑sized vent one pipe size for its entire length, the table’s maximum length limits do not apply to that vent per § 904.2 — but you still must size the vent for the total DFU and observe the minimum diameter rules.

Are trap arms counted toward the maximum DFU for a vertical stack?

Table 703.2 normally lists drainage DFU excluding the trap arm where noted; always read the table notes and Chapter 10 trap/trap‑arm tables for the correct counting method.

What is the effect of reduced slope on horizontal fixture‑unit capacity?

Table 703.2 assumes 1/4 in./ft slope; if the slope is reduced to 1/8 in./ft, multiply horizontal fixture‑unit capacity by the factor listed in the table notes (see Table 703.2 notes).

Where do wet‑vent limits appear?

Wet‑vent developed‑length and sizing limits are in § 908.0 et seq.; for example, § 908.1 limits many wet‑vent lengths to 6 ft and prescribes required upsizing where applicable.

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Related in the CPC

Fixture connections — inlet fittings and single-vertical drainage conditions

How to size drains and vents using drainage fixture units (DFU)

System sizing & fixture units

California Plumbing Code