CPC · California Plumbing Code
What are the vent pipe rise, grade and connection requirements (drip-back, inverts)?
Vents must be installed so liquids won’t collect: no sags, vents either level or sloped to drain back to the fixture drain, tie into horizontal drains above the drain centerline downstream of the trap, and each vent must rise at least 6 inches above the fixture flood rim before offsetting or joining other vents (exceptions only where structural conditions prohibit it) — see CPC §§905.1, 905.2, 905.3 .
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
In plain English: vent piping must be arranged so it does not trap water and any condensate or liquid in the vent will flow back to the drain it serves. Specifically, vents must be free of drops or sags and be level or graded to drip back to the drainage pipe (see § 905.1). Where a vent ties into a horizontal drain its invert must be taken off above the drain centerline downstream of the trap (§ 905.2). Each vent must rise vertically at least 6 inches above the fixture flood‑level rim before offsetting or joining other vents unless structural conditions prohibit that rise (§ 905.3) .
The single most important rule: vents must be free of sags and arranged so any liquid in the vent flows back to the drain it serves (drip‑back) — § 905.1 .
Requirements in detail
1) Grade / drip‑back
- The vent and any branch vent must be free from drops or sags; they must be either level or graded so liquid will drip back by gravity into the drainage pipe served. This is the controlling requirement for vent trenches, horizontal vent runs and offsets (§ 905.1) .
- The CPC does not give a numeric slope for “graded to drip back” in § 905.1; the performance requirement (no sags, positive return to the drain) is the standard.
2) Invert location when connecting to a horizontal drain
- When a vent connects into a horizontal drainage pipe, the vent invert (the bottom of the vent at its connection) must be taken off above the drainage centerline of that horizontal drain, and the connection point must be downstream of the trap being served (§ 905.2) .
- Practical result: the vent connection must be on the top half of the drain pipe section and located downstream of the trap outlet so effluent flows away from the trap.
3) Vertical rise before offset/connection
- Each vent shall rise vertically to a point of at least 6 inches (152 mm) above the fixture flood‑level rim before any horizontal offset is permitted (§ 905.3) .
- Where two or more vents converge, each vent must rise the same minimum 6 inches above the flood‑level rim of the fixture it serves before being connected to any other vent (§ 905.3) .
- If a vent is installed less than 6 inches above the flood‑level rim, the vent must be installed with approved drainage fittings, materials and grade to the drain (i.e., the vent must be treated as a drained fitting and sloped/constructed so liquids return to the drain) (§ 905.3) .
Decision‑relevant quick table
| Requirement | Key value / action | Code Reference |
|---|---|---|
| Vent free of drops/sags; level or graded to drip back | No sags; must return to drain by gravity | § 905.1 |
| Vent connection to horizontal drain — invert location | Invert taken off above drain centerline; connect downstream of the trap | § 905.2 |
| Minimum vertical rise before offset or joining other vents | 6 inches (152 mm) above fixture flood‑level rim | § 905.3 |
| Vents < 6 inches above flood rim | Must use approved drainage fittings/material and grade to the drain | § 905.3 |
Exceptions & special cases
- Structural limitation: the 6‑inch vertical rise may be waived when prohibited by structural conditions; in that case the installation must comply with any alternate method approved by the Authority Having Jurisdiction (this allowance is recognized in § 905.3) .
- When a vent is shorter than 6 inches above the flood rim, the code requires that the vent portion be installed with approved drainage fittings/material and graded to the drain — treat that segment like a drained fitting and ensure positive flow back to the drain (§ 905.3) .
- The code does not give a numeric slope for “graded to drip back.” Where exact slope is needed (for long horizontal vent runs, island fixtures, radon systems, etc.) follow the applicable product/manufacturer guidance and the Authority Having Jurisdiction’s accepted practices (see related provisions for special venting rules) .
Common mistakes
- Allowing horizontal vent runs to sag or form low spots (which trap liquid) — violates § 905.1. Always support and slope or level vents so liquids return to the drain .
- Tying a vent into a horizontal drain with the invert below the centerline or upstream of the trap — violates § 905.2; the invert must be above centerline and downstream of the trap .
- Offsetting or tying vents together below the required 6‑inch rise above the flood rim for each vent — violates § 905.3 unless properly detailed with approved drainage fittings/material and grade, or unless structural conditions justify otherwise .
- Assuming a specific slope (e.g., 1/4" per foot) is mandated by these sections — the CPC language in § 905.1 is performance‑based (free of sags; drip‑back). Don’t invent a numeric slope unless it comes from another applicable section, manufacturer instruction, or AHJ direction .
Worked example — concrete scenario
Scenario: a lavatory sink has a flood‑level rim at 34 inches above finished floor; the trap arm runs into a horizontal building drain just downstream of the fixture. You plan to run a 1½" vent.
- Vertical rise requirement: the vent must rise vertically to at least 6 inches above the flood‑level rim before any horizontal offset. So 34" + 6" = 40" above finished floor. You must bring the vent straight up to 40" before turning it horizontally or tying into another vent (§ 905.3) .
- Connection to horizontal drainage: when you connect the vent into the horizontal drain, the invert of the vent connection must be taken off above the drainage centerline of that horizontal drain and the connection must be downstream of the trap outlet being served (§ 905.2) .
- Horizontal routing: if the vent runs horizontally in the attic or under floor, it must be free from drops or sags and be level or graded so any condensate or entrained liquid will drip back to the sink drain. The code does not specify a numeric slope, so ensure no low spots and use supports/grades that achieve positive return to the drain (§ 905.1) .
- If you cannot achieve the 6" vertical rise because of a structural beam, document the restriction and work with the AHJ for an accepted alternative; the code recognizes that structural conditions may prohibit the rise (§ 905.3) .
Related provisions
- Vent pipe size and maximum horizontal vent length: § 904.1 and § 904.2 (vent sizing/length limits) .
- Roof termination and clearance requirements for vents: § 906.1 and § 906.2 (roof termination height and clearances) .
- Special venting (island fixtures) and foot/return vents: § 909.1 (island fixtures) — contains additional drainage/grade notes for returned vents under sinks, etc. .
- Combination waste and vent systems and vent connection rules: § 910.3–910.6 (where permitted/vent sizing/cleanouts) — consult where conventional layouts aren’t possible .
- General prohibited practices: § 310.4 (use of vent and waste pipes) — warns against using vents as waste pipes and vice versa .
If you need, I can produce a simple sketch showing the proper rise, offset, and the invert tie‑in to a horizontal drain for your exact fixture location and building constraints.
Code references
Grounded in the retrieved California Plumbing Code — click a citation to read the verbatim passage:
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.
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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 § 904.2 High 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 § 905.1 High 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 § 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 § 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 § 908.2.4 Medium relevance — show source text
908.2.4 Water Closet. The water closet fixture drain or trap arm connection to the wet vent shall be downstream of fixture drain or trap arm connections to the horizontal wet vent.
908.2.5 Additional Fixtures. Additional fixtures shall discharge downstream of the wet vent system and be conventionally vented. Only the fixtures within the bathroom group shall connect to the wet-vented horizontal branch.
909.0 Special Venting for Island Fixtures. 909.1 General. Traps for island sinks and similar equipment shall be roughed in above the floor and shall be permitted to be vented by extending the vent as high as possible, but not less than the drainboard height and then returning it downward and connecting it to the horizontal sink drain immediately downstream from the vertical fixture drain. The return vent shall be connected to the horizontal drain through a wyebranch fitting and shall, in addition, be provided with a foot vent taken off the vertical fixture vent by means of a wye branch immediately below the floor and extending to the nearest partition and then through the roof to the open air, or shall be permitted to be connected to other vents at a point not less than 6 inches (152 mm) above the flood-level rim of the fixtures served. Drainage fittings shall be used on the vent below the floor level, and a slope of not less than [1] ⁄ 4 inch per foot (20.8 mm/m) back to the drain shall be maintained. The return bend used under the drainboard shall be a one-piece
fitting or an assembly of a 45 degree (0.79 rad), a 90 degree (1.57 rad), and a 45 degree (0.79 rad) elbow in the order named. Pipe sizing shall be as elsewhere required in this code. The island sink drain, upstream of the returned vent, shall serve no other fixtures. An accessible cleanout shall be installed in the vertical portion of the foot vent.
910.0 Combination Waste and Vent Systems. 910.1 Where Permitted. Combination waste and vent systems shall be permitted where structural conditions preclude the installation of conventional systems as otherwise prescribed by this code. 910.2 Approval. Construction documents for each combination waste and vent system shall first be approved by the Authority Having Jurisdiction before a portion of such system is installed.
910.3 Vents. Each combination waste and vent system, as defined in Chapter 2, shall be provided with a vent or vents adequate to ensure free circulation of air. A branch exceeding 15 feet (4572 mm) in length shall be separately vented in an approved manner. The area of a vent installed in a combination waste and vent system shall be not less than one-half the inside cross-sectional area of the drainpipe served. The vent connection shall be downstream of the uppermost fixture. 910.4 Connections and Size. Branches serving traps shall connect to the main line at an angle not exceeding 2 percent. Each waste pipe and each trap in such a system shall be not less than two pipe sizes exceeding the sizes required by Chapter 7 of this code, and not less than two pipe sizes exceeding a fixture tailpiece or connection. 910.5 Vertical Waste Pipe. No vertical waste pipe shall be used in such a system, except the tailpiece or connection between the outlet of a plumbing fixture and the trap. Such tailpieces or connections shall be as short as possible, and in no case shall exceed 2 feet (610 mm).
CPC § 501.5 Medium relevance — show source text
The inlet compartment of any septic tank shall be not less than two-thirds of the total capacity of the tank, nor less than 500 gallons (1892 L) liquid capacity, and shall be not less than 3 feet (914 mm) in width and 5 feet (1524 mm) in length. Liquid depth shall be not less than 2 [1] ⁄ 2 feet (762 mm) nor more than 6 feet (1829 mm). The secondary compartment of a septic tank shall have a capacity of not less than 250 gallons (946 L) and a capacity not exceeding one-third of the total capacity of such tank. In septic tanks having a 1500 gallon (5678 L) capacity, the secondary compartment shall be not less than 5 feet (1524 mm) in length.
H 501.5 Access. Access to each septic tank shall be provided by not less than two manholes 20 inches (508 mm) in minimum dimension or by an equivalent removable cover slab. One access manhole shall be located over the inlet, and one access manhole shall be located over the outlet. Where a first compartment exceeds 12 feet (3658 mm) in length, an additional manhole shall be provided over the baffle wall. H 501.6 Pipe Opening Sizes. The inlet and outlet pipe openings shall not be larger in size than the connecting sewer pipe. The vertical leg of round inlet and outlet fittings shall not be less in size than the connecting sewer pipe nor less than 4 inches (100 mm) in diameter. A baffle-type fitting shall have the equivalent cross-sectional area of the connecting sewer pipe and not less than a 4 inch (102 mm) horizontal dimension where measured at the inlet and outlet pipe inverts. H 501.7 Pipe Extension. The inlet and outlet pipe or baffle shall extend 4 inches (102 mm) above and not less than 12 inches (305 mm) below the water surface. The invert of the inlet pipe shall be at a level not less than 2 inches (51 mm) above the invert of the outlet pipe. H 501.8 Free Vent Area. Inlet and outlet pipe fittings or baffles and compartment partitions shall have a free vent area equal to the required cross-sectional area of the house sewer or private sewer discharging therein to provide free ventilation above the water surface from the disposal field or seepage pit through the septic tank, house sewer, and stack to the outer air.
H 501.9 Sidewalls. The sidewalls shall extend not less than 9 inches (229 mm) above the liquid depth. The cover of the septic tank shall be not less than 2 inches (51 mm) above the back vent openings.
H 501.10 Partitions and Baffles. Partitions or baffles between compartments shall be of solid, durable material and shall extend not less than 4 inches (102 mm) above the liquid level. The transfer port between compartments shall be a minimum size equivalent to the tank inlet, but in no case less than 4 inches (102 mm) in size, shall be installed in the inlet compartment side of the baffle so that the entry into the port is placed 65 percent to 75 percent in the depth of the liquid. Wooden baffles are prohibited. H 501.11 Structural Design. The structural design of septic tanks shall comply with the following requirements:
CPC § 0.0162 Medium relevance — show source text
per square foot| |Lead-coated high-yield copper|0.0162 nominal|—|ASTM B101, 12 oz. per square foot| |Painted terne|—|—|20| |Stainless steel|—|28|—| |Zinc alloy|0.027|—|—| |For SI: 1 inch = 25.4 mm, 1 pound = 0.454 kg, 1 square foot = 0.93 m2.|For SI: 1 inch = 25.4 mm, 1 pound = 0.454 kg, 1 square foot = 0.93 m2.|For SI: 1 inch = 25.4 mm, 1 pound = 0.454 kg, 1 square foot = 0.93 m2.|For SI: 1 inch = 25.4 mm, 1 pound = 0.454 kg, 1 square foot = 0.93 m2.|
R905.2.8.3 Sidewall flashing. Base flashing against a vertical sidewall shall be continuous or step flashing and shall be not less than 4 inches (102 mm) in height and 4 inches (102 mm) in width and shall direct water away from the vertical sidewall onto the roof or into the gutter. Where siding is provided on the vertical sidewall, the vertical leg of the flashing shall be continuous under the siding. Where anchored masonry veneer is provided on the vertical sidewall, the base flashing shall be provided in accordance with this section and counterflashing shall be provided in accordance with Section R703.8.2.2. Where exterior plaster or adhered masonry veneer is provided on the vertical sidewall, the base flashing shall be provided in accordance with this section and Section R703.7.3.
R905.2.8.4 Other flashing. Flashing against a vertical front wall, as well as soil stack, vent pipe and chimney flashing, shall be applied in accordance with the asphalt shingle manufacturer’s instructions.
R905.2.8.5 Drip edge. A drip edge shall be provided at eaves and rake edges of shingle roofs. Adjacent segments of drip edge shall be overlapped not less than 2 inches (51 mm). Drip edges shall extend not less than [1] / 4 inch (6.4 mm) below the roof sheathing and extend up back onto the roof deck not less than 2 inches (51 mm). Drip edges shall be mechanically fastened to the roof deck at not more than 12 inches (305 mm) o.c. with fasteners as specified in Section R905.2.5. Underlayment shall be installed over the drip edge along eaves and under the drip edge along rake edges.
R905.3 Clay and concrete tile. The installation of clay and concrete tile shall comply with the provisions of this section.
R905.3.1 Sheathing requirements. Concrete and clay tile shall be installed over wood structural panels or solid lumber sheathing.
Exception: Spaced lumber sheathing in accordance with Section R803.1 shall be permitted in Seismic Design Categories A, B and C.
CPC § 5.3 Medium relevance — show source text
BE103.5.3 Vent pipe. A plumbing tee or other approved connection shall be inserted horizontally beneath the sheeting and connected to a 3- or 4-inch-diameter (76 or 102 mm) fitting with a vertical vent pipe installed through the sheeting. The vent pipe shall be extended up through the building floors, and terminate not less than 12 inches (305 mm) above the roof in a location not less than 10 feet (3048 mm) away from any window or other opening into the conditioned spaces of the building that is less than 2 feet (610 mm) below the exhaust point, and 10 feet (3048 mm) from any window or other opening in adjoining or adjacent buildings.
BE103.6 Passive subslab depressurization system. In basement or slab-on-grade buildings, the following components of a passive subslab depressurization system shall be installed during construction.
BE103.6.1 Vent pipe. A minimum 3-inch-diameter (76 mm) ABS, PVC or equivalent gastight pipe shall be embedded vertically into the subslab aggregate or other permeable material before the slab is cast. A “T” fitting or equivalent method shall be used to ensure that the pipe opening remains within the subslab permeable material. Alternatively, the 3-inch (76 mm) pipe shall be inserted directly into an interior perimeter drain tile loop or through a sealed sump cover where the sump is exposed to the subslab aggregate or connected to it through a drainage system.
The pipe shall be extended up through the building floors, and terminate not less than 12 inches (305 mm) above the surface of the roof in a location not less than 10 feet (3048 mm) away from any window or other opening into the conditioned spaces of the building that is less than 2 feet (610 mm) below the exhaust point, and 10 feet (3048 mm) from any window or other opening in adjoining or adjacent buildings.
BE103.6.2 Multiple vent pipes. In buildings where interior footings or other barriers separate the subslab aggregate or other gaspermeable material, each area shall be fitted with an individual vent pipe. Vent pipes shall connect to a single vent that terminates above the roof or each individual vent pipe shall terminate separately above the roof.
APPENDIX BE-10 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
APPENDIX BE — RADON CONTROL METHODS
BE103.7 Vent pipe drainage. Components of the radon vent pipe system shall be installed to provide positive drainage to the ground beneath the slab or soil-gas-retarder.
BE103.8 Vent pipe accessibility. Radon vent pipes shall be accessible for future fan installation through an attic or other area outside the habitable space.
Exception: The radon vent pipe need not be accessible in an attic space where an approved roof-top electrical supply is provided for future use.
BE103.9 Vent pipe identification. Exposed and visible interior radon vent pipes shall be identified with not less than one label on each floor and in accessible attics. The label shall read: “Radon Reduction System.”
BE103.10 Combination foundations. Combination basement/crawl space or slab-on-grade/crawl space foundations shall have separate radon vent pipes installed in each type of foundation area. Each radon vent pipe shall terminate above the roof or shall be connected to a single vent that terminates above the roof.
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,
190 2025 CALIFORNIA PLUMBING CODE
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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 § 6-8 Medium relevance — show source text
Col1 Col2 Col3 Col4 NUMBER OF APPLIANCES: Col6 TWO OR MORE Col8 APPLIANCE TYPE: APPLIANCE TYPE: DRAFT HOOD-EQUIPMENT DRAFT HOOD-EQUIPMENT APPLIANCE VENT CONNECTION: APPLIANCE VENT CONNECTION: DIRECT TO PIPE OR VENT DIRECT TO PIPE OR VENT VENT CONNECTOR CAPACITY VENT CONNECTOR CAPACITY VENT CONNECTOR CAPACITY VENT CONNECTOR CAPACITY VENT CONNECTOR CAPACITY VENT CONNECTOR CAPACITY VENT CONNECTOR DIAMETER –****D (inch) VENT CONNECTOR DIAMETER –****D (inch) VENT CONNECTOR DIAMETER –****D (inch) VENT CONNECTOR DIAMETER –****D (inch) VENT CONNECTOR DIAMETER –****D (inch) VENT CONNECTOR DIAMETER –****D (inch) TOTAL VENT
HEIGHT
H
(feet)CONNECTOR
RISE
R
(feet)3 4 5 6 7 8 TOTAL VENT
HEIGHT
H
(feet)CONNECTOR
RISE
R
(feet)MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR 6-8 1
2
321
28
3440
53
6168
86
98102
124
147146
178
204205
235
27515 1
2
323
30
3544
56
6477
92
102117
134
155179
194
216240
265
29830
and up1
2
325
31
3649
58
6884
97
107129
145
164190
211
232270
295
321Col1 COMMON VENT CAPACITY Col3 Col4 Col5 Col6 Col7 Col8 COMMON VENT DIAMETER –****D (inch) **COMMON VENT CPC § 1210.5.3 Medium relevance — show source text
1210.5.3 Ventilation. A chase shall be ventilated to the outdoors and only at the top. The opening(s) shall have a minimum free area [in square inches (square meters)] equal to the product of one-half of the maximum pressure in the piping [in pounds per square inch (kilopascals)] times the largest nominal diameter of that piping [in inches (millimeters)], or the cross-sectional area of the chase, whichever is smaller. Where more than one fuel gas piping system is present, the free area for each system shall be calculated and the largest area used. [NFPA 54:7.4.3] 1210.6 Gas Pipe Turns. Changes in direction of gas pipe shall be made by the use of fittings, factory bends, or field bends. [NFPA 54:7.5] 1210.6.1 Metallic Pipe. Metallic pipe bends shall comply with the following:
(1) Bends shall be made only with bending tools and procedures intended for that purpose.
(2) All bends shall be smooth and free from buckling, cracks, or other evidence of mechanical damage.
(3) The longitudinal weld of the pipe shall be near the neutral axis of the bend.
(4) Pipe shall not be bent through an arc of more than 90 degrees.
(5) The inside radius of a bend shall be not less than 6 times the outside diameter of the pipe. [NFPA 54:7.5.1] 1210.6.2 Plastic Pipe. Plastic pipe bends shall comply with the following:
(1) The pipe shall not be damaged, and the internal diameter of the pipe shall not be effectively reduced.
(2) Joints shall not be located in pipe bends.
(3) The radius of the inner curve of such bends shall not be less than 25 times the inside diameter of the pipe.
(4) Where the piping manufacturer specifies the use of special bending tools or procedures, such tools or procedures shall be used. [NFPA 54:7.5.2] 1210.6.3 Elbows. Factory-made welding elbows or transverse segments cut therefrom shall have an arc length measured along the crotch of at least 1 inch (25.4 mm) for pipe sizes 2 inches (50 mm) and larger. [NFPA 54:7.5.3]
226 2025 CALIFORNIA PLUMBING CODE
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FUEL GAS PIPING
1210.7 Drips and Sediment Traps. For other than dry gas conditions, a drip shall be provided at any point in the line of pipe where condensate could collect. Where required by the Authority Having Jurisdiction or the serving gas supplier, a drip shall also be provided at the outlet of the meter. This drip shall be installed so as to constitute a trap wherein an accumulation of condensate shuts off the flow of gas before it runs back into the meter. [NFPA 54:7.6.1]
Frequently asked questions
Why must a vent rise 6 inches above the flood‑level rim before offsetting?
Because the code requires a vertical rise of 6 inches to keep offsets above the fixture flood level and reduce the chance of liquids entering the vent line or draining back into traps; this is specified in § 905.3 .
What does “drip back” mean in practice?
“Drip back” means the vent pipe must be arranged so any liquid that enters the vent will flow by gravity back into the building drainage it serves (no low spots or sags). This is the performance requirement in § 905.1 .
Where exactly do I take the invert when tying a vent into a horizontal drain?
Take the vent invert above the centerline of the horizontal drainage pipe and make the connection downstream of the trap being served, per § 905.2 .
The vent can't physically rise 6 inches — what then?
The code allows that when the 6‑inch rise is prohibited by structural conditions an alternative may be used, but you must obtain AHJ approval and where vents are less than 6 inches they must be installed with approved drainage fittings, materials and grade to the drain (§ 905.3) .
Does the CPC specify an exact slope for horizontal vents?
No — § 905.1 requires vents to be free from drops or sags and be level or graded to drip back, but it does not list a numeric slope. If a numeric slope is required for a special system or manufacturer, follow that guidance and the AHJ’s direction .
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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