CPC · California Plumbing Code
Sizing vent stacks, branch vents and when to increase vent size
If a soil/waste stack rises five or more branch intervals you must provide a vent stack; if a branch vent’s developed length exceeds 40 feet you must upsize that vent one full pipe size for its entire length. Measure developed length from the lowest branch‑vent connection to outdoor termination and follow Table C401.1 for base sizing; special rules apply for horizontal offsets and yoke vents (see §§ C401.2–C401.4).
Last reviewed: July 6, 2026
What the code requires — plain English
- A vent stack is required when a drainage stack rises five or more branch intervals above the building drain or horizontal branch — measure the vent stack's developed length from the lowest branch-vent connection to its termination outdoors (§ C401.2) .
- If a branch vent has a developed length greater than 40 feet (12 192 mm), you must increase that vent one pipe size for the entire developed length (§ C401.3) .
- When a drainage stack includes a horizontal offset that has five or more branch intervals above the offset, the upper and lower portions of that offset must be vented in the manner required by § C401.4 and its subsections (§ C401.4) .
The single most important rule: if a branch vent is longer than 40 feet, increase its diameter by one full pipe size for its entire developed length; if a stack rises five or more branch intervals, provide a separate vent stack.
Requirements in detail
Key defined terms (first-use emphasis)
- Vent stack — the vertical vent pipe serving a drainage stack that must be provided when the stack rises five or more branch intervals (§ C401.2) .
- Branch vent — a vent serving a horizontal branch or group of fixtures whose required diameter depends on fixture units and developed length; subject to the 40‑foot increase rule (§ C401.3) .
- Developed length — the length of the vent measured along its centerline from the lowest connection of the branch vent to the vent termination outdoors (used for vent stack and branch-vent limits) (§ C401.2) .
Decision table — thresholds and sizing actions
| Decision question | Code action (what you must do) | Key value / threshold | Code Reference |
|---|---|---|---|
| Does the drainage stack need a vent stack? | Provide a vent stack (separate vertical vent) | 5 or more branch intervals above building drain/horizontal branch | § C401.2 |
| How to measure vent-stack length | Measure from lowest branch-vent connection to outdoor termination | — | § C401.2 |
| When must a branch vent be upsized? | Increase the vent one pipe size for entire developed length | > 40 ft (12 192 mm) developed length | § C401.3 |
| When must a horizontal stack offset be vented? | Vent the upper and lower sections per C401.4.1/ C401.4.2 | 5 or more branch intervals above offset | § C401.4 |
| Where should the upper vent-stack connect if tied to building drain? | Connection must be downstream of the drainage stack and within 10 × stack diameter | 10 × diameter of drainage stack | § C401.4.1 |
| How to vent the lower section below an offset | Use a yoke vent connecting between the offset and the next lower branch with a wye-branch fitting; size per code | Yoke vent size must not be less than required for vent serving the drainage stack (see code) | § C401.4.2 |
| How to select vent diameter for a stack/vent | Use fixture-unit totals and developed length (see Table C401.1 and Tables 703.2/304.3) | Table-driven — vent must be at least 1¼ in and not less than ½ the diameter of the drain it serves | § C401.1 and Table C401.1 |
Notes: Table C401.1 (size & length of vents) and the Tables for fixture units (Tables 703.2 / C304.3 / C304.2) determine basic vent diameters and maximum developed lengths; if the branch vent crosses the 40‑ft threshold you must increase the entire length by one pipe size regardless of shorter-table values (§ C401.3, Table C401.1) .
How the offset venting rules work (C401.4 series)
- If an offset causes five or more branch intervals above it, the stack is effectively split into an upper section and lower section; each must be vented separately per § C401.4.1 and § C401.4.2. The upper section gets a separate vent stack that connects at the base of the drainage stack and must connect below the lowest horizontal branch or building drain; if that vent stack ties into the building drain the tie must be downstream of the drainage stack and within 10 × the stack diameter (§ C401.4.1) . The lower section is vented with a yoke vent between the offset and the next lower horizontal branch using a wye-branch; the yoke vent and its connection size are governed by § C401.4.2 (and related yoke‑vent rules elsewhere) .
Exceptions & special cases
- The CPC limits and exceptions for vent sizing (minimum vent diameters, minimum as 1¼ in, and that vents be at least ½ the size of the drain they serve) still apply — see § C401.1 and Table references for minimums and fixture-unit-based sizing .
- Where structural conditions prevent the standard approach you may need an engineered vent system designed by a registered design professional; engineered vent systems are permitted and must meet Section § 912.0 requirements (design & AHJ approval) — see related provisions below .
- The code gives detailed sizing and maximum lengths in Table C401.1 (size vs. developed length vs. fixture units). Use that table first, then apply the C401.3 “+1 size if >40 ft” rule if applicable .
- Some yoke‑vent and multi‑story venting details are governed elsewhere (for example, § 907.1 / § 907.2 cover yoke‑vent placement and sizing when vents are used for tall stacks); use those sections where vertical/height-specific rules apply .
If you need a requirement but it is not present in the retrieved excerpts above, I will say so plainly — I have cited the specific CPC sections available in the provided files.
Common mistakes
- Failing to measure developed length correctly — you must measure along the vent centerline from the lowest branch‑vent connection to the outdoor termination when checking both vent-stack and branch vent limits (§ C401.2) .
- Forgetting the 40‑ft rule: installers sometimes increase the vent only for the portion over 40 ft; the code requires the vent to be increased one full pipe size for the entire developed length when the developed length exceeds 40 ft (§ C401.3) .
- Overlooking offset venting: when there are five or more branch intervals above a horizontal offset, both upper and lower sections must be properly vented per § C401.4; treating the stack as continuous without separate venting can violate the code .
- Connecting the upper vent stack incorrectly to the building drain: if you tie the vent stack into the building drain it must be downstream of the drainage stack and within 10 × the drainage stack diameter (§ C401.4.1) .
- Ignoring minimum vent diameters and the rule that vent pipe diameter cannot be less than one‑half the diameter of the drain it serves — verify with § C401.1 and Table C401.1 .
Worked example — concrete scenario
Scenario:
- A building has a 4‑inch diameter soil/waste drainage stack. The stack has branch connections on each floor (one branch interval per floor). The stack rises six branch intervals above the building drain (i.e., six floors). One of the branch vents has a developed length of 45 ft.
Apply the code:
- Is a vent stack required? Yes — the stack extends six branch intervals, which is ≥ five, so provide a vent stack for the drainage stack per § C401.2. Measure the vent-stack developed length from the lowest branch-vent connection to outdoors when checking compliance (§ C401.2) .
- Branch-vent sizing: the branch vent’s developed length is 45 ft, which exceeds 40 ft. Per § C401.3, you must increase the branch vent one pipe size for its entire developed length. If the table (Table C401.1) would have allowed, say, a 1½‑inch vent for the fixture‑unit load, you must increase it to 2 inches for the full 45‑ft length because of the >40‑ft rule (§ C401.3) .
- Offset connection checks (if the stack has a horizontal offset and there are six branch intervals above that offset): vent the upper section as a separate vent stack; if the upper vent connects to the building drain, the connection must be downstream of the drainage stack and within 10 × the stack diameter. For a 4‑inch stack that means the connection must be within 40 inches (10 × 4 in) downstream of the stack per § C401.4.1 .
- Lower section: use a yoke vent between the offset and the next lower branch with a wye fitting and size it per § C401.4.2 (yoke‑vent sizing is not less than the required size for the vent serving the drainage stack) . Also note yoke‑vent placement rules in § 907.2 (minimum height above floor) when applicable .
This example shows how the simple numeric thresholds (5 branch intervals, 40 ft, 10× diameter) drive required changes; always verify final vent diameters using Table C401.1 and fixture‑unit tables referenced in Chapter 7 and Appendix C .
Related provisions (quick reference)
- § C401.1 — Size of vents; minimum diameters and rule that a vent be at least ½ the size of the drainage pipe served .
- Table C401.1 — Size and maximum developed length of vents (use to determine basic vent size before applying C401.3 increase) .
- § 904.1 / § 904.2 — General vent size and horizontal‑length limitations for minimum‑sized vents (one‑third horizontal limit) .
- § 907.1 / § 907.2 — Vent stacks, yoke‑vent placement and sizing for tall stacks (yoke vent placement, sizing rules) .
- § 912.0 — Engineered vent systems (when standard prescriptive methods cannot be used) .
- Definitions: Yoke Vent definition and related text (see definitions / § 227.0) .
Code references
Grounded in the retrieved California Plumbing Code — click a citation to read the verbatim passage:
CPC § 304.3.1 High relevance — show source text
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.
C 401.3 Branch Vents. Where branch vents exceed 40 feet (12 192 mm) in developed length, such vent shall be increased by one pipe size for the entire developed length of the vent pipe. C 401.4 Venting Horizontal Offsets. Drainage stacks with horizontal offsets shall be vented where five or more branch intervals are located above the offset. The upper and lower section of the horizontal offset shall be vented in accordance
with Section C 401.4.1 and Section C 401.4.2.
C 401.4.1 Venting Upper Section. The vent for the upper section of the stack shall be vented as a separate stack with a vent stack connection installed at the base of the drainage stack. Such vent stack shall connect below the lowest horizontal branch or building drain. Where vent stack connects to the building drain, the connection shall be located downstream of the drainage stack and within a distance of 10 times the diameter of the drainage stack. C 401.4.2 Venting Lower Section. The vent for the lower section of the stack shall be vented by a yoke vent connecting between the offset and the next lower horizontal branch using a wye-branch fitting. The size of the yoke vent and connection shall be not less in diameter
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APPENDIX C
TABLE C 303.3 DRAINAGE FIXTURE UNIT VALUES (DFU) FOR BATHROOM GROUPS [1, 2]
CPC § 401.3 High relevance — show source text
C 401.3 Branch Vents. Where branch vents exceed 40 feet (12 192 mm) in developed length, such vent shall be increased by one pipe size for the entire developed length of the vent pipe. C 401.4 Venting Horizontal Offsets. Drainage stacks with horizontal offsets shall be vented where five or more branch intervals are located above the offset. The upper and lower section of the horizontal offset shall be vented in accordance
with Section C 401.4.1 and Section C 401.4.2.
C 401.4.1 Venting Upper Section. The vent for the upper section of the stack shall be vented as a separate stack with a vent stack connection installed at the base of the drainage stack. Such vent stack shall connect below the lowest horizontal branch or building drain. Where vent stack connects to the building drain, the connection shall be located downstream of the drainage stack and within a distance of 10 times the diameter of the drainage stack. C 401.4.2 Venting Lower Section. The vent for the lower section of the stack shall be vented by a yoke vent connecting between the offset and the next lower horizontal branch using a wye-branch fitting. The size of the yoke vent and connection shall be not less in diameter
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APPENDIX C
TABLE C 303.3 DRAINAGE FIXTURE UNIT VALUES (DFU) FOR BATHROOM GROUPS [1, 2]
Col1 PRIVATE USE BATHROOM GROUP SERVING 3 OR MORE PRIVATE
USE BATHROOM GROUPBathroom Groups having 1.6 GPF Gravity-Tank Water Closets Bathroom Groups having 1.6 GPF Gravity-Tank Water Closets Bathroom Groups having 1.6 GPF Gravity-Tank Water Closets Half-Bath or Powder Room 3.0 2.0 1 Bathroom Group 5.0 3.0 11⁄2 Bathrooms 6.0 3.5 2 Bathrooms 7.0 4.5 21⁄2 Bathrooms 8.0 5.0 3 Bathrooms 9.0 5.5 Each Additional1⁄2 Bath 0.5 0.5 Each Additional Bathroom Group 1.0 1.0 Bathroom Groups having 1.6 GPF Pressure-Tank Water Closets Bathroom Groups having 1.6 GPF Pressure-Tank Water Closets Bathroom Groups having 1.6 GPF Pressure-Tank Water Closets Half-Bath or Powder Room 3.5 2.5 1 Bathroom Group 5.5 3.5 11⁄2 Bathrooms 6.5 4.0 2 Bathrooms 7.5 5.0 21⁄2 Bathrooms 8.5 5.5 3 Bathrooms 9.5 6.0 Each Additional1⁄2 Bath 0.5 0.5 Each Additional Bathroom Group 1.0 1.0 Bathroom Groups having 3.5 GPF Gravity-Tank Water Closets Bathroom Groups having 3.5 GPF Gravity-Tank Water Closets Bathroom Groups having 3. CPC § 2025 High relevance — show source text
Chapter 7 Sanitary Drainage.
This chapter regulates the design and installation of sanitary drainage systems to ensure they will work as intended. Drainage piping should not be oversized nor undersized, and constructed of approved materials to guard against fouling, deposit of solids, clogging, and with cleanouts so arranged that the pipes may be readily cleaned. The purpose of the sanitary drainage system is to remove effluent discharged from plumbing fixtures and other equipment to an approved point of disposal, such as a public sanitary system or private sewage disposal system.
The basics of a sanitary drainage system include public and private sewage disposal; selection of materials; installation of the building drain and sewer; joining methods for pipe and fittings; drainage fixture units for sizing the drainage system; sumps and ejectors; vent sizing and length of vents; and testing.
Chapter 8 Indirect Wastes.
Chapter 8 regulates indirect waste connections that are required for plumbing fixtures and plumbing appliances dealing with food preparation, dishwashing, potable liquids, and similar equipment. An indirect connection prevents sewage from backing up into a fixture or appliance, thus providing protection against potential health hazards. The waste pipe discharges through an air gap or air break into a waste receptor or standpipe. The protection in the form of an air gap is necessary when the contamination is a potential health hazard or cross connection with the potable water system. Where there is no possibility of contaminating the potable water (nonpotable discharge), the indirect waste pipe may connect in the form of an air break. This method is often preferred to prevent splashing. In addition, health care facilities and special wastes must be protected from contamination that may result from the connection to the drainage system. The waste must be treated to prevent any damage to the piping or sewage treatment process. Waste receptors are sized and designed to prevent splashing and allow for peak discharge conditions.
Chapter 9 Vents.
Chapter 9 regulates the material, design, and installation of vents. A vent system is a pipe or pipes installed in a drainage system that provide a flow of air to and from the system to ventilate it, provide a circulation of air to eliminate trap siphonage, and reduce back-pressure and vacuum surge. In addition, vents provide the rapid and silent flow of waste without exposing occupants of the building to any sewer gases. Proper installation of vents is crucial, as a telltale sign that there is a problem in the drain and vent system is related to the elevation of the horizontal portion of the venting. Venting is not limited to sanitary drainage systems. Venting methods are applicable to other drainage systems such as those for chemical waste, graywater waste, and clear water waste. Sizing the venting system is directly tied to the design of the drainage system. For example, the velocities in the drainage system and its peak flow rates affect the diameters in the venting system. Where the vertical distance between a fixture outlet and trap is excessive, velocities in the entire drainage system will be greater than those in the vent sizing table. All venting methods in this chapter are categorized as either dry vents or wet vents. Vent stacks, stack vents, branch vents, island vents, relief vents, and individual vents are dry vents. Wet vents (horizontal or vertical), circuit vents, combination drain and vents are versions of “wet venting” in which the vent is wetted by drainage flow.
2025 CALIFORNIA PLUMBING CODE xv
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 § 601.2 High relevance — show source text
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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 HEIGHTSTACK 75 FEET TO LESS THAN
160 FEET IN HEIGHTSTACK 160 FEET OR
GREATER IN HEIGHT3 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.
C 601.8 Prohibited Connections Near Base of Stack. Where stacks are more than 75 feet (22 860 mm) high, a separate stack shall be provided for the fixtures on the lower two stories. The stack for the lower two stories shall be permitted to be connected to the branch of the building drain that serves the stack for the upper stories at a point that is not less than 8 feet (2438 mm) downstream from the base of the upper stack. Where stacks are less than 75 feet (22 860 mm) high but more than two stories high, the lowest story shall not connect within 8 feet (2438 mm) downstream from the base of the stack. Venting for the lowest story shall be provided in accordance with Section C 601.8.1 and Section C 601.8.2.
C 601.8.1 Conditional Vent. Venting of fixtures on the lowest floor shall be in accordance with Section 908.0 through Section 911.5 and may connect into the single-stack as a conditional vent. The conditional vent connects into the stack by means of a wye-fitting to prevent ingress of drainage into the vent. No more than 12 drainage fixture units (DFU) may be connected into the conditional vent and shall connect not less than 8 feet (2438 mm) above the stack base.
C 601.8.2 Other Branch Vent. Other branch vents shall be vented in accordance with Section 908.0 through Section 911.5.
CPC § 901.0 Medium relevance — show source text
TABLE OF CONTENTS
CHAPTER 9 VENTS . . . . . . . . . . . . . . . . . . . . .187
901.0 General . . . . . . . . . . . . . . . . . . . . .189
901.1 Applicability . . . . . . . . . . . . . . . . . .189
901.2 Vents Required . . . . . . . . . . . . . . .189
901.3 Trap Seal Protection . . . . . . . . . . .189
902.0 Vents Not Required . . . . . . . . . . .189
902.1 Interceptor . . . . . . . . . . . . . . . . . .189
902.2 Bars, Soda Fountains, and Counter . . . . . . . . . . . . . . . . . . . . .189
903.0 Materials . . . . . . . . . . . . . . . . . . . .189
903.1 Applicable Standards . . . . . . . . . .189
903.2 Use of Copper or Copper Alloy Tubing . . . . . . . . . . . . . . . . .189
903.3 Changes in Direction . . . . . . . . . .189
904.0 Size of Vents . . . . . . . . . . . . . . . .189
904.1 Size . . . . . . . . . . . . . . . . . . . . . . . .189
904.2 Length . . . . . . . . . . . . . . . . . . . . . .189
905.0 Vent Pipe Grades and Connections . . . . . . . . . . . . . . . . .190
905.1 Grade . . . . . . . . . . . . . . . . . . . . . .190
905.2 Horizontal Drainage Pipe . . . . . . .190
905.3 Vent Pipe Rise . . . . . . . . . . . . . . .190
905.4 Roof Termination . . . . . . . . . . . . .190
905.5 Location of Opening . . . . . . . . . . .190
905.6 Common Vertical Pipe . . . . . . . . .190
906.0 Vent Termination . . . . . . . . . . . . .190
906.1 Roof Termination . . . . . . . . . . . . .190
906.2 Clearance . . . . . . . . . . . . . . . . . . .190
906.3 Use of Roof . . . . . . . . . . . . . . . . .190
906.4 Outdoor Installations . . . . . . . . . . .190
906.5 Joints . . . . . . . . . . . . . . . . . . . . . .190
906.6 Lead . . . . . . . . . . . . . . . . . . . . . . .190
906.7 Frost or Snow Closure . . . . . . . . .190
907.0 Vent Stacks and Relief Vents . . . .190
907.1 Drainage Stack . . . . . . . . . . . . . . .190
907.2 Yoke Vent . . . . . . . . . . . . . . . . . . .190
CPC § 601.2.1 Medium relevance — show source text
Not more than two water closets shall be permitted to discharge to a 3 inch (80 mm) stack. Stacks shall be uniformly sized based on the total connected drainage fixture unit load, with no reductions in size. C 601.2.1 Stack Vent. The drainage stack vent shall have a stack vent of the same size terminating to the outdoors. C 601.3 Branch Size. Horizontal branches connecting to a single-stack vent system shall be sized in accordance with Table 703.2.
Exceptions:
(1) Not more than one water closet within 18 inches (457 mm) of the stack horizontally shall be permitted on a 3 inch (80 mm) horizontal branch.
(2) A water closet within 18 inches (457 mm) of a stack horizontally and one other fixture with up to 1 [1] ⁄ 2 inch (40 mm) fixture drain size shall be permitted on a 3 inch (80 mm) horizontal branch where connected to the stack through a sanitary tee. C 601.4 Length of Horizontal Branches. Water closets shall be not more than 4 feet (1219 mm) horizontally from the stack.
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.
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APPENDIX C
CPC § 2025 Medium relevance — show source text
The waste must be treated to prevent any damage to the piping or sewage treatment process. Waste receptors are sized and designed to prevent splashing and allow for peak discharge conditions.
Chapter 9 Vents.
Chapter 9 regulates the material, design, and installation of vents. A vent system is a pipe or pipes installed in a drainage system that provide a flow of air to and from the system to ventilate it, provide a circulation of air to eliminate trap siphonage, and reduce back-pressure and vacuum surge. In addition, vents provide the rapid and silent flow of waste without exposing occupants of the building to any sewer gases. Proper installation of vents is crucial, as a telltale sign that there is a problem in the drain and vent system is related to the elevation of the horizontal portion of the venting. Venting is not limited to sanitary drainage systems. Venting methods are applicable to other drainage systems such as those for chemical waste, graywater waste, and clear water waste. Sizing the venting system is directly tied to the design of the drainage system. For example, the velocities in the drainage system and its peak flow rates affect the diameters in the venting system. Where the vertical distance between a fixture outlet and trap is excessive, velocities in the entire drainage system will be greater than those in the vent sizing table. All venting methods in this chapter are categorized as either dry vents or wet vents. Vent stacks, stack vents, branch vents, island vents, relief vents, and individual vents are dry vents. Wet vents (horizontal or vertical), circuit vents, combination drain and vents are versions of “wet venting” in which the vent is wetted by drainage flow.
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FORMAT OF THE UNIFORM PLUMBING CODE
Chapter 10 Traps and Interceptors.
Chapter 10 regulates the material, design, and installation of traps, interceptors, and separators. Traps are required on drainage type plumbing fixtures and must be self-scouring without interior partitions. Interceptors, on the other hand, are designed to control what goes down a drain. Interceptors are used to keep harmful substances from entering the sanitary drainage system, such as grease, sand, oil and other materials. The retained materials need periodic removal to maintain efficiency and function of the separating device. The capacity of an interceptor is based on retention and flow rate. There are many types of interceptors that are used at beauty salons, hospitals, meat, fish or foul packaging, refineries, repair garages, gas stations, car washing facilities, various plants, factories, and processing sites. The designer of the building is responsible for locating interceptors with the expectation for the frequency of maintenance, ease of cleaning and floor space for equipment.
Chapter 11 Storm Drainage.
Chapter 11 regulates the removal of stormwater from roofs, yards, paved areas, and similar areas. The objective of storm drainage systems is to provide a conduit or channel through which runoff will be carried from a point of collection to a point of disposal; this protects the property and the public from the uncontrolled flow of runoff and ensures that drains and inlets are adequately sized to receive the volume of runoff that flows to the drains. For the purpose of system design, it’s necessary to specify the duration of a selected storm.
CPC § 301.3. Medium relevance — show source text
form plumbing design work. Details are necessary to ensure compliance with the requirements of this section, together with a full description of the complete installation including quality, grade of materials, equipment, construction, and methods of assembly and installation. Components, materials, and equipment shall comply with standards and specifications listed in Chapter 17 of this code or approved by the Authority Having Jurisdiction and other national consensus standards applicable to plumbing systems and materials. Where such standards and specifications are not available, alternate materials and equipment shall be approved in accordance with Section 301.3.
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APPENDIX C
Col1 Col2 TABLE C 401.1 SIZE AND LENGTH OF VENTS Col4 Col5 Col6 Col7 Col8 Col9 Col10 Col11 SIZE OF
SOIL OR
WASTE
STACK
(inches)FIXTURE
UNITS
CONNECTEDDIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) SIZE OF
SOIL OR
WASTE
STACK
(inches)FIXTURE
UNITS
CONNECTED11⁄4 11⁄2 2 21⁄2 3 4 5 6 8 SIZE OF
SOIL OR
WASTE
STACK
(inches)FIXTURE
UNITS
CONNECTEDMAXIMUM LENGTH OF VENT (feet) MAXIMUM LENGTH OF VENT (feet) MAXIMUM LENGTH OF VENT (feet) MAXIMUM LENGTH OF VENT (feet) MAXIMUM LENGTH OF VENT (feet) MAXIMUM LENGTH OF VENT (feet) MAXIMUM LENGTH OF VENT (feet) MAXIMUM LENGTH OF VENT (feet) MAXIMUM LENGTH OF VENT (feet) 11⁄2 8 50 150 –– –– –– –– –– –– –– 2 12 30 75 200 –– –– –– –– –– –– 2 20 26 50 150 –– –– –– –– –– –– 21⁄2 42 –– 30 1 CPC § 910.0 Medium relevance — show source text
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).
Exception: Branch lines shall be permitted to have 45 degree (0.79 rad) vertical offsets.
910.6 Cleanouts. An accessible cleanout shall be installed in each vent for the combination waste and vent system. Cleanouts shall not be required on a wet-vented branch serving a single trap where the fixture tailpiece or connection is not less than 2 inches (50 mm) in diameter and provides ready access for cleaning through the trap.
910.7 Fixtures. No water closet or urinal shall be installed on such a system. Other one, two, or three unit fixtures remotely located from the sanitary system and adjacent to a combination waste and vent system shall be permitted to be connected to such system in the conventional manner by means of waste and vent pipes of regular sizes, providing that the two pipe size increase required in Section 910.4 is based on the total fixture unit load connected to the system.
See Appendix B of this code for explanatory notes on the design of combination waste and vent systems.
911.0 Circuit Venting. 911.1 Circuit Vent Permitted. A maximum of eight flooroutlet water closets, showers, bathtubs, or floor drains con
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VENTS
nected to a horizontal branch shall be permitted to be circuit vented. Each trap arm shall connect horizontally to the horizontal branch being circuit vented in accordance with Table 1002.2. The horizontal branch shall be classified as a drain and a vent from the most downstream trap arm connection to the most upstream trap arm connection to the horizontal branch.
Exception: Back-outlet and wall-hung water closets shall be permitted to be circuit vented provided that no floor-outlet fixtures are connected to the same horizontal branch. Backoutlet and wall-hung water closets shall connect horizontally to the horizontal circuit vented drain.
CPC § 904.2 Medium relevance — show source text
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.
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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. 905.4 Roof Termination. Vent pipes shall extend undiminished in size above the roof, or shall be reconnected with soil or waste vent of the proper size. 905.5 Location of Opening. The vent pipe opening from soil or waste pipe shall not be below the weir of the trap.
Exception: Water closets and similar fixtures. 905.6 Common Vertical Pipe. Two fixtures shall be permitted to be served by a common vertical pipe where each such fixture wastes separately into an approved double fitting having inlet openings at the same level.
906.0 Vent Termination.
906.1 Roof Termination. Each vent pipe or stack shall extend through its flashing and shall terminate vertically not less than 6 inches (152 mm) above the roof nor less than 1 foot (305 mm) from a vertical surface. ABS and PVC piping exposed to sunlight shall be protected by water based synthetic latex paints.
906.2 Clearance. Each vent shall terminate not less than 10 feet (3048 mm) from, or not less than 3 feet (914 mm) above, an openable window, door, opening, air intake, or vent shaft, or not less than 3 feet (914 mm) in every direction from a lot line, alley and street excepted. 906.2.1 [OSHPD 1,1R, 2, 3, 4 & 5] Each vent pipe shall terminate not less than twenty-five (25) feet (7620 mm) from any air intake or vent shaft. 906.3 Use of Roof. Vent pipes shall be extended separately or combined, of full required size, not less than 6 inches (152 mm) above the roof or firewall. Flagpoling of vents shall be prohibited except where the roof is used for assembly purposes or parking.
CPC § 911.2.1 Medium relevance — show source text
waste.
911.2.1 Multiple Circuit Vents. When multiple circuit vents are interconnected according to Section 911.4.1, each individual circuit vent shall be sized according to Section 911.2. The vent pipe connecting each circuit vent shall be sized according to Table 703.2.
911.3 Relief Vent. A 2 inch (50 mm) relief vent shall be provided for circuit-vented horizontal branches receiving the discharge of four or more water closets when connecting to a drainage stack that receives the discharge of soil or waste from upper horizontal branches.
911.3.1 Connection and Installation. The relief vent
shall connect to the horizontal branch between the stack and the most downstream trap arm of the circuit vent. The relief vent shall be installed on the vertical to the
horizontal branch.
911.3.2 Fixture Drain. The relief vent is permitted to serve as a fixture drain. Fixtures discharging to a relief vent shall be one or two fixture unit fixtures but shall not
exceed a total of 4 fixture units.
911.4 Slope and Size of Horizontal Branch. The vented section of the horizontal branch shall be uniformly sloped and not more than 1 inch per foot (83.3 mm/m). The entire length of the vented section of the horizontal branch shall be sized for the total drainage discharge to the branch according to Table 703.2.
911.4.1 Multiple Circuit-Vented Branches. Circuitvented horizontal branches are permitted to be connected together. Each group of a maximum of eight fixtures shall be considered a separate circuit vent and shall be in accordance with Section 911.4.1.1 and Section 911.4.1.2.
911.4.1.1 Size of Parallel Horizontal
Branches. Parallel horizontal circuit vented branches shall be permitted to connect on the same floor level. Each separate circuit-vented horizontal branch that is interconnected shall be sized independently in accordance with Section 911.4.
911.4.1.2 Size of Continuous Horizontal Branches. Two or more circuit vented systems continuous on the same horizontal branch shall be uniformly sized for the total discharge into the branch.
911.5 Additional Fixtures. Fixtures, other than the circuitvented fixtures, are permitted to discharge to the horizontal branch drain. Such fixtures shall be located on the same floor as the circuit-vented fixtures and shall be either individually or common vented.
912.0 Engineered Vent System. 912.1 General. The design and sizing of a vent system shall be permitted to be determined by accepted engineering practices. The system shall be designed by a registered design professional and approved in accordance with Section 301.5. 912.2 Minimum Requirements. An engineered vent system shall provide protection of the trap seal in accordance with Section 901.3.
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CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE
CHAPTER 10 - TRAPS AND INTERCEPTORS
(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 § 907.2 Medium relevance — show source text
907.2 Yoke Vent. The yoke vent connection to the vent stack shall be placed not less than 42 inches (1067 mm) above the floor level, and the yoke vent connection to the drainage stack shall be using a wye-branch fitting placed below the lowest drainage branch connection serving that floor.
908.0 Wet Venting. 908.1 Vertical Wet Venting. Wet venting is limited to vertical drainage piping receiving the discharge from the trap arm of one and two fixture unit fixtures that also serves as a vent not exceeding four fixtures. Wet-vented fixtures shall be within the same story; provided, further, that fixtures with a continuous vent discharging into a wet vent shall be within the same story as the wet-vented fixtures. No wet vent shall exceed 6 feet (1829 mm) in developed length. 908.1.1 Size. The vertical piping between two consecutive inlet levels shall be considered a wet-vented sec tion. Each wet-vented section shall be not less than one pipe size exceeding the required minimum waste pipe size of the upper fixture or shall be one pipe size exceeding the required minimum pipe size for the sum of the fixture units served by such wet-vented section, whichever is larger, but in no case less than 2 inches (50 mm) in diameter. 908.1.2 Vent Connection. Common vent sizing shall be the sum of the fixture units served but, in no case,
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VENTS
smaller than the minimum vent pipe size required for a fixture served, or by Section 904.0. 908.2 Horizontal Wet Venting for a Bathroom Group. A bathroom group located on the same floor level shall be permitted to be vented by a horizontal wet vent where all of the conditions of Section 908.2.1 through Section 908.2.5 are met.
908.2.1 Vent Connection. The dry vent connection to the wet vent shall be an individual vent for the bidet, shower, or bathtub. One or two vented lavatory(s) shall be permitted to serve as a wet vent for a bathroom group. Only one wet-vented fixture drain or trap arm shall discharge upstream of the dry-vented fixture drain connection. Dry vent connections to the horizontal wet vent shall be in accordance with Section 905.2 and Section
905.3.
908.2.2 Size. The wet vent shall be sized based on the fixture unit discharge into the wet vent. The wet vent shall be not less than 2 inches (50 mm) in diameter for 4 drainage fixture units (dfu) or less, and not less than 3 inches (80 mm) in diameter for 5 dfu or more. The dry vent shall be sized in accordance with Table 702.1 and Table 703.2 based on the total fixture units discharging into the wet vent.
908.2.3 Trap Arm. The length of the trap arm shall not exceed the limits in Table 1002.2. The trap size shall be in accordance with Section 1003.3. The vent pipe opening from the horizontal wet vent, except for water closets and similar fixtures, shall not be below the weir of the trap.
CPC § 906.4 Medium relevance — show source text
906.4 Outdoor Installations. Vent pipes for outdoor installations shall extend not less than 10 feet (3048 mm) above the surrounding ground and shall be securely supported.
906.5 Joints. Joints at the roof around vent pipes shall be made watertight by the use of approved flashings or flashing material.
906.6 Lead. (See Chapter 17) Sheet lead shall comply with the following:
(1) For safe pans – not less than 4 pounds per square foot (lb/ft [2] ) (19 kg/m [2] ) or [1] ⁄ 16 of an inch (1.6 mm) thick. (2) For flashings or vent terminals – not less than 3 lb/ft [2] (15 kg/m [2] ) or 0.0472 of an inch (1.2 mm) thick. (3) Lead bends and lead traps shall be not less than [1] ⁄ 8 of an inch (3.2 mm) in wall thickness.
906.7 Frost or Snow Closure. Where frost or snow closure is likely to occur in locations having minimum design temperature below 0°F (-17.8°C), vent terminals shall be not less than 3 inches (76 mm) in diameter, but in no event smaller than the required vent pipe. The change in diameter shall be made inside the building not less than 1 foot (305 mm) below the roof in an insulated space and terminate not less than 10 inches (254 mm) above the roof, or in accordance with the Authority Having Jurisdiction.
907.0 Vent Stacks and Relief Vents.
907.1 Drainage Stack. Each drainage stack that extends 10 or more stories shall be served by a parallel vent stack, which shall extend undiminished in size from its upper terminal and connect to the drainage stack at or immediately below the lowest fixture drain. Each such vent stack shall also be connected to the drainage stack at each fifth floor, counting down from the uppermost fixture drain, using a yoke vent, the size of which shall be not less in diameter than either the drainage or the vent stack, whichever is smaller.
907.2 Yoke Vent. The yoke vent connection to the vent stack shall be placed not less than 42 inches (1067 mm) above the floor level, and the yoke vent connection to the drainage stack shall be using a wye-branch fitting placed below the lowest drainage branch connection serving that floor.
908.0 Wet Venting. 908.1 Vertical Wet Venting. Wet venting is limited to vertical drainage piping receiving the discharge from the trap arm of one and two fixture unit fixtures that also serves as a vent not exceeding four fixtures. Wet-vented fixtures shall be within the same story; provided, further, that fixtures with a continuous vent discharging into a wet vent shall be within the same story as the wet-vented fixtures. No wet vent shall exceed 6 feet (1829 mm) in developed length. 908.1.1 Size. The vertical piping between two consecutive inlet levels shall be considered a wet-vented sec tion. Each wet-vented section shall be not less than one pipe size exceeding the required minimum waste pipe size of the upper fixture or shall be one pipe size exceeding the required minimum pipe size for the sum of the fixture units served by such wet-vented section, whichever is larger, but in no case less than 2 inches (50 mm) in diameter. **908.1.2 Vent Connection.
CPC § 501.0 Medium relevance — show source text
THAN THREE BRANCH INTERVALS**| |DIAMETER OF
PIPE
(inches)|HORIZONTAL FIXTURE
BRANCH1|ONE STACK OF THREE
OR FEWER BRANCH
INTERVALS|TOTAL FOR STACK|TOTAL AT ONE BRANCH
INTERVAL| |11⁄2|3|4|8|2| |2|6|10|24|6| |21⁄2|12|20|42|9| |3|202|482|722|202| |4|160|240|500|90| |5|360|540|1100|200| |6|620|960|1900|350| |8|1400|2200|3600|600| |10|2500|3800|5600|1000| |12|3900|6000|8400|1500| |15|7000|6000|8400|1500|For SI units: 1 inch = 25 mm
Notes:
1 Does not include branches of the building drain.
2 A maximum of two water closets or bathroom groups within each branch interval or more than six water closets or bathroom groups on the stack.
than the required size for the vent serving the drainage stack. The yoke vent connection shall be permitted to be a vertical extension of the drainage stack.
C 501.0 Vacuum Drainage Systems. C 501.1 General. This section regulates the design and installation provisions for vacuum waste drainage systems. Plans for vacuum waste drainage systems shall be submitted to the Authority Having Jurisdiction for approval and shall be considered an engineered designed system. Such plans shall be prepared by a registered design professional to per
form plumbing design work. Details are necessary to ensure compliance with the requirements of this section, together with a full description of the complete installation including quality, grade of materials, equipment, construction, and methods of assembly and installation. Components, materials, and equipment shall comply with standards and specifications listed in Chapter 17 of this code or approved by the Authority Having Jurisdiction and other national consensus standards applicable to plumbing systems and materials. Where such standards and specifications are not available, alternate materials and equipment shall be approved in accordance with Section 301.3.
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APPENDIX C
Col1 Col2 TABLE C 401.1 SIZE AND LENGTH OF VENTS Col4 Col5 Col6 Col7 Col8 Col9 Col10 Col11 SIZE OF
SOIL OR
WASTE
STACK
(inches)FIXTURE
UNITS
CONNECTEDDIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) DIAMETER OF VENT REQUIRED (inches) **DIAMETER OF VENT REQUIRED CPC § 83.3 Medium relevance — show source text
000|12 000|
For SI units: 1 inch = 25 mm, 1 inch per foot = 83.3 mm/m
Notes:
1 On-site sewers that serve more than one building shall be permitted to be sized according to the current standards and specifications of the administrative authority for public sewers.
2 A maximum of two water closets or two bathroom groups, except in single-family dwellings, where a maximum of three water closets or three bathroom groups shall be permitted to be installed.
Col1 TABLE C 304.3 HORIZONTAL FIXTURE BRANCHES AND STACKS Col3 Col4 Col5 DIAMETER OF
PIPE
(inches)MAXIMUM NUMBER OF DRAINAGE FIXTURE UNITS MAXIMUM NUMBER OF DRAINAGE FIXTURE UNITS MAXIMUM NUMBER OF DRAINAGE FIXTURE UNITS MAXIMUM NUMBER OF DRAINAGE FIXTURE UNITS DIAMETER OF
PIPE
(inches)HORIZONTAL FIXTURE
BRANCH1ONE STACK OF THREE
OR FEWER BRANCH
INTERVALSSTACKS WITH MORE THAN THREE BRANCH INTERVALS STACKS WITH MORE THAN THREE BRANCH INTERVALS DIAMETER OF
PIPE
(inches)HORIZONTAL FIXTURE
BRANCH1ONE STACK OF THREE
OR FEWER BRANCH
INTERVALSTOTAL FOR STACK TOTAL AT ONE BRANCH
INTERVAL11⁄2 3 4 8 2 2 6 10 24 6 21⁄2 12 20 42 9 3 202 482 722 202 4 160 240 500 90 5 360 540 1100 200 6 620 960 1900 350 8 1400 2200 3600 600 10 2500 3800 5600 1000 12 3900 6000 8400 1500 15 7000 6000 8400 1500 For SI units: 1 inch = 25 mm
Notes:
1 Does not include branches of the building drain.
2 A maximum of two water closets or bathroom groups within each branch interval or more than six water closets or bathroom groups on the stack.
than the required size for the vent serving the drainage stack. The yoke vent connection shall be permitted to be a vertical extension of the drainage stack.
C 501.0 Vacuum Drainage Systems. C 501.1 General. This section regulates the design and installation provisions for vacuum waste drainage systems. Plans for vacuum waste drainage systems shall be submitted to the Authority Having Jurisdiction for approval and shall be considered an engineered designed system. Such plans shall be prepared by a registered design professional to per
CPC § 907.0 Medium relevance — show source text
907.0, 911.3, 1009.4
Required . . . . . . . . . . . . . . . . . . . . . . . . . . .901.2, 904.1
Required separately
on every trap . . . . . . . . . . . . . . . .901.2, 1002.1, 1002.2 Sizing . . . . . . . . . . . . . .Table 702.1, 703.0, Table 703.2,
904.0, 908.1.1, 908.1.2,
908.2.2, 910.4, C 401.0,
Table C 401.1, C 601.2
Special . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .909.0
Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . .224.0, 906.1,
907.0, C 401.2, C 601.2
Sump . . . . . . . . . . . . . . . . . . . .710.7, 710.10, 710.13.3,
810.1, Table 810.1
System, definition . . . . . . . . . . . . . . . . . . . . . . . . .224.0
Termination . . . . . . . . . . . . . . . . . .905.4, 906.0, 906.2.1
Testing . . . . . . . . . . . . . . . . . . . . . . . . . .712.0, 1504.10 Trap seal protection . . . . . . . . . . . . . . . . . .901.3, 1002.0
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
CPC § 905.1 Medium relevance — show source text
905.1 Grade . . . . . . . . . . . . . . . . . . . . . .190
905.2 Horizontal Drainage Pipe . . . . . . .190
905.3 Vent Pipe Rise . . . . . . . . . . . . . . .190
905.4 Roof Termination . . . . . . . . . . . . .190
905.5 Location of Opening . . . . . . . . . . .190
905.6 Common Vertical Pipe . . . . . . . . .190
906.0 Vent Termination . . . . . . . . . . . . .190
906.1 Roof Termination . . . . . . . . . . . . .190
906.2 Clearance . . . . . . . . . . . . . . . . . . .190
906.3 Use of Roof . . . . . . . . . . . . . . . . .190
906.4 Outdoor Installations . . . . . . . . . . .190
906.5 Joints . . . . . . . . . . . . . . . . . . . . . .190
906.6 Lead . . . . . . . . . . . . . . . . . . . . . . .190
906.7 Frost or Snow Closure . . . . . . . . .190
907.0 Vent Stacks and Relief Vents . . . .190
907.1 Drainage Stack . . . . . . . . . . . . . . .190
907.2 Yoke Vent . . . . . . . . . . . . . . . . . . .190
908.0 Wet Venting . . . . . . . . . . . . . . . . .190
908.1 Vertical Wet Venting . . . . . . . . . . .190
908.2 Horizontal Wet Venting for a Bathroom Group . . . . . . . . . . . . . .191
909.0 Special Venting for Island Fixtures . . . . . . . . . . . . . . . . . . . . .191
909.1 General . . . . . . . . . . . . . . . . . . . . .191
910.0 Combination Waste and Vent
Systems . . . . . . . . . . . . . . . . . . . .191
910.1 Where Permitted . . . . . . . . . . . . . .191
910.2 Approval . . . . . . . . . . . . . . . . . . . .191
910.3 Vents . . . . . . . . . . . . . . . . . . . . . .191
910.4 Connections and Size . . . . . . . . .191
910.5 Vertical Waste Pipe . . . . . . . . . . .191
910.6 Cleanouts . . . . . . . . . . . . . . . . . . .191
910.7 Fixtures . . . . . . . . . . . . . . . . . . . . .191
911.0 Circuit Venting . . . . . . . . . . . . . . .191
911.1 Circuit Vent Permitted . . . . . . . . .191
911.2 Circuit Vent Size and
Connection . . . . . . . . . . . . . . . . . .192
CPC § 226.0 Medium relevance — show source text
226.0 – X –
No definitions.
227.0 – Y –
Yoke Vent. A pipe connecting upward from soil or waste stack to a vent stack to prevent pressure changes in the stacks.
228.0 – Z –
No definitions.
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CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE
CHAPTER 3 - GENERAL REGULATIONS
(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
Adopt Entire Chapter
Adopt Entire Chapter as
amended (amended
sections listed below)
Adopt only those sections
that are listed below
Chapter/Section
301.3
301.3.1
301.3.1.1
301.3.1.2
301.4.1
301.7
301.8
303.1 Exception
304.1 Exception
310.11
310.12
310.13
310.14
310.15
311.1 Note
312.2
312.7
312.11
313.8
321.0
322.0
323.0BSC BSC-
CGSFM HCD Col6 Col7 DSA Col9 Col10 OSHPD Col12 Col13 Col14 Col15 Col16 Col17 BSCC DPH AGR DWR CEC CA SL SLC Adopting Agency
Adopt Entire Chapter
Adopt Entire Chapter as
amended (amended
sections listed below)
Adopt only those sections
that are listed below
Chapter/Section
301.3
301.3.1
301.3.1.1
301.3.1.2
301.4.1
301.7
301.8
303.1_Exception_
304.1_Exception_
310.11
310.12
310.13
310.14
310.15
311.1_ Note_
312.2
312.7
312.11
313.8
321.0
322.0
_323.California Plumbing Code Medium relevance — show source text
OF APPLIANCES: SINGLE**
APPLIANCE TYPE: CATEGORY I
APPLIANCE VENT CONNECTION: CONNECTED DIRECTLY TO VENT
VENT DIAMETER –****D (inch)
3
4
5
6
7
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|NUMBER OF APPLIANCES: SINGLE
APPLIANCE TYPE: CATEGORY I
APPLIANCE VENT CONNECTION: CONNECTED DIRECTLY TO VENT
VENT DIAMETER –****D (inch)
3
4
5
6
7
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|APPLIANCE VENT CONNECTION:|APPLIANCE VENT CONNECTION:|APPLIANCE VENT CONNECTION:|APPLIANCE VENT CONNECTION:|APPLIANCE VENT CONNECTION:|APPLIANCE VENT CONNECTION:|** CONNECTED DIRECTLY TO VENT**|** CONNECTED DIRECTLY TO VENT**|** CONNECTED DIRECTLY TO VENT**|** CONNECTED DIRECTLY TO VENT**|** CONNECTED DIRECTLY TO VENT**|** CONNECTED DIRECTLY TO VENT**| |NUMBER OF APPLIANCES: SINGLE
APPLIANCE TYPE: CATEGORY I
APPLIANCE VENT CONNECTION: CONNECTED DIRECTLY TO VENT
VENT DIAMETER –****D (inch)
3
4
5
6
7
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|NUMBER OF APPLIANCES: SINGLE
APPLIANCE TYPE: CATEGORY I
APPLIANCE VENT CONNECTION: CONNECTED DIRECTLY TO VENT
VENT DIAMETER –****D (inch)
3
4
5
6
7
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)|VENT DIAMETER –****D (inch)| |NUMBER OF APPLIANCES: SINGLE
**APPLIANCE TYPE: CATEGORYCPC § 3.3.187 Medium relevance — show source text
44 2025 CALIFORNIA PLUMBING CODE
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
DEFINITIONS
Water Main (Street Main). A water supply pipe for public or community use.
Water Station. A designated location intended to provide access to drinking water through a device or appliance.
Water Supply System. The building supply pipe, the water distribution pipes, and the necessary connecting pipes, fittings, control valves, backflow prevention devices, and all appurtenances carrying or supplying potable water in or adjacent to the building or premises.
Water/Wastewater Utility. A public or private entity which may treat, deliver or do both functions to reclaimed (recycled) water, potable water, or both to wholesale or retail cus tomers.
Welder, Pipe. A person who specializes in the welding of pipes and holds a valid certificate of competency from a recognized testing laboratory, based on the requirements of the ASME Boiler and Pressure Vessels code, Section IX.
Wet Procedure Locations. The area in a patient care space where a procedure is performed that is normally subject to wet conditions while patients are present, including standing fluids on the floor or drenching of the work area, either of which condition is intimate to the patient or staff. [NFPA 99:3.3.187]
Wet Vent. A vent that also serves as a drain.
Whirlpool Bathtub. A bathtub fixture equipped and fitted with a circulating piping system designed to accept, circulate, and discharge bathtub water upon each use.
226.0 – X –
No definitions.
227.0 – Y –
Yoke Vent. A pipe connecting upward from soil or waste stack to a vent stack to prevent pressure changes in the stacks.
228.0 – Z –
No definitions.
2025 CALIFORNIA PLUMBING CODE 45
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
46 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
CHAPTER 3 - GENERAL REGULATIONS
(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
Adopt Entire Chapter
Adopt Entire Chapter as
amended (amended
sections listed below)
Adopt only those sections
that are listed below
Chapter/Section
301.3
301.3.1
301.3.1.1
301.3.1.2
301.4.1
301.7
301.8
303.1 Exception
304.1 Exception
310.11
310.12
310.13
310.14
310.15
311.1 Note
312.2
312.7
312.11
313.8
321.0
322.0
323.
Frequently asked questions
When exactly do I measure developed length for the 40‑ft rule?
Measure along the centerline of the vent from the lowest branch‑vent connection to the outdoor vent termination; that developed length is what determines whether § C401.3 applies .
If a branch vent is 41 ft, do I increase only the portion beyond 40 ft?
No — § C401.3 requires the branch vent to be increased one pipe size for the entire developed length when the developed length exceeds 40 ft; you do not partial‑size the run — increase the entire vent length .
What counts as a “branch interval” when checking the 5‑interval rule?
A branch interval is the interval of the stack that serves a floor/level of branch connections; when a drainage stack extends five or more branch intervals above the building drain or horizontal branch, a vent stack is required per § C401.2 .
Where can I find the exact vent diameters for a given fixture load?
Use Table C401.1 (Size and Length of Vents) along with the fixture‑unit tables (Tables in Chapter 7 / Appendix C) to pick the starting vent diameter, then apply the 40‑ft upsizing rule and minimum‑diameter rules in § C401.1 .
If I have an offset with fewer than five branch intervals above it, do I still need special venting?
No — § C401.4 is triggered when the offset has five or more branch intervals above it. If fewer than five intervals are above the offset, the standard venting rules (no split vent stack required) apply; other offset‑related provisions (like prohibited connections within 2 ft) still apply elsewhere in the code .
Are engineered solutions allowed instead of the prescriptive rules?
Yes — an engineered vent system designed by a registered design professional is permitted when justified and must meet § 912.0 requirements and AHJ approval .
More in California Plumbing Code
- Administration
- Definitions
- General Regulations
- Plumbing Fixtures and Fixture Fittings
- Water Heaters
- Water Supply and Distribution
- Sanitary Drainage (Drain, Waste, and Vent)
- Indirect Wastes
- Vents
- Traps and Interceptors
- Storm Drainage
- Fuel Gas Piping
- Health Care Facilities — Medical Gas and Medical Vacuum Systems
- Alternate Water Sources and Nonpotable Rainwater Catchment Systems
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