CPC · California Plumbing Code
Venting island fixtures: return vents and foot vents
For a homeowner: island sinks must be roughed above the floor and use a special vent arrangement — the vent goes up at least to the sink’s drainboard, returns to the horizontal drain, and includes a below‑floor “foot vent” that goes to the roof or ties into other vents high enough above the sink. The code (CPC §909.1) also requires specific fittings, slope and an accessible cleanout so the system vents and drains properly.
Last reviewed: July 6, 2026
What the code requires
Island sinks and similar island fixtures must have their traps roughed above the floor and may be vented using a return vent (extended up at least to the drainboard height and returned down to the horizontal sink drain) plus a foot vent (taken off the vertical vent immediately below the floor and run to roof or tied into other vents at least 6 inches (152 mm) above the flood-level rim). These requirements appear in § 909.0 and § 909.1 of the California Plumbing Code.
The single most important rule: island sinks must have the trap roughed above the floor and be vented by a return vent and a foot vent arranged exactly as described in § 909.1.
Requirements in detail
Key terms (first mention bolded)
- Return vent — the vent extended up (to at least the drainboard height) and then returned downward to connect to the horizontal sink drain. § 909.1.
- Foot vent — a vent taken off the vertical fixture vent by means of a wye branch immediately below the floor that extends to a partition and then through the roof to open air, or alternatively tied into other vents at a specified height. § 909.1.
- Drainboard height — the minimum elevation the return vent must reach before being brought back down; the code uses this building feature as the required minimum elevation. § 909.1.
Quick decision table (dimensions/values you must check)
| Requirement | Value / detail | Code Reference |
|---|---|---|
| Trap rough-in elevation | Above the floor (traps for island sinks roughed in above the floor) | § 909.1 |
| Minimum height for return vent before returning downward | Not less than the drainboard height | § 909.1 |
| How return vent connects to horizontal drain | Connect through a wye‑branch fitting to the horizontal sink drain immediately downstream from the vertical fixture drain | § 909.1 |
| Foot vent routing option A | Foot vent taken off vertical vent by wye immediately below floor, extend to nearest partition, then through the roof to open air | § 909.1 |
| Foot vent routing option B | Or foot vent may be connected to other vents at a point not less than 6 inches (152 mm) above the flood‑level rim of fixtures served | § 909.1 |
| Fittings and slope below floor | Drainage fittings required on the vent below the floor; slope of not less than 1/4 inch per foot (20.8 mm/m) back to the drain | § 909.1 |
| Return bend configuration | Must be a one‑piece fitting or an assembly of 45°–90°–45° elbows (in that order) under the drainboard | § 909.1 |
| Pipe sizing | “Pipe sizing shall be as elsewhere required in this code” — size per applicable vent/drain sizing tables and sections | § 909.1 |
| Upstream fixture prohibition | The island sink drain upstream of the returned vent shall serve no other fixtures | § 909.1 |
| Cleanout | Accessible cleanout required in the vertical portion of the foot vent | § 909.1 |
Notes on construction details
- The code explicitly requires the vertical foot‑vent takeoff by a wye immediately below the floor; this is intended to avoid sharp, obstructive fittings at that junction. § 909.1.
- Where the foot vent ties into other vents instead of running to the roof, the tie‑in must be at or above 6 inches (152 mm) above the fixtures’ flood‑level rim so it cannot be submerged during flood conditions. § 909.1.
- The code requires drainage fittings on the vent below the floor so the below‑floor configuration behaves as a drainage run (and the slope back to the drain is required). § 909.1.
Exceptions & special cases
- The code explicitly allows two alternative foot‑vent terminations: (1) extend the foot vent to the roof via the nearest partition; or (2) connect it to other vents provided the connection point is not less than 6 inches (152 mm) above the flood‑level rim of the fixtures served. These are both in § 909.1.
- The code does not supply special reduced sizing for island vent piping; it defers to general vent sizing rules (i.e., “pipe sizing shall be as elsewhere required in this code”). Designers must therefore use the usual vent sizing tables for the actual fixture units served. § 909.1.
- If you need additional or alternative engineered venting solutions (for unusual layouts or multi‑fixture banks), consult other venting methods in Chapter 9 (wet vents, circuit vents, combination systems) — these are treated elsewhere in Chapter 9 and must be applied only where permitted. See e.g., § 908.0 and § 910.0.
If you need a local code interpretation (e.g., when roof penetration routing is impractical), get approval from the Authority Having Jurisdiction — the code references AHJ approval for alternate systems elsewhere (see combination waste/vent approval language in § 910.2).
Common mistakes
- Routing the trap below the finished floor (island traps must be roughed in above the floor). Violates § 909.1.
- Failing to provide an accessible cleanout in the vertical portion of the foot vent — often overlooked on concealed island pedestals. Required by § 909.1.
- Connecting other fixtures to the portion of the island sink drain that lies upstream of the returned vent (the code prohibits serving other fixtures upstream). § 909.1.
- Using an incorrect fitting for the return bend (must be a one‑piece return bend or the 45°–90°–45° assembly in that order). § 909.1.
- Omitting the required slope (≥ 1/4 in/ft) on the vent below the floor; remember that the vent run below floor level is treated with drainage fittings and must slope back toward the drain. § 909.1.
Worked example
Scenario: island sink with a 3" horizontal sink drain; the manufacturer’s drainboard top is at 36 inches above finished floor (drainboard height = 36"). The trap outlet is roughed above the floor in the island cabinet.
Action plan (apply § 909.1):
- Rough the trap above the floor inside the island cabinet (meets “roughed in above the floor”). § 909.1.
- Extend the vent vertically from the trap outlet up to at least the drainboard height — in this example to 36 inches — then bring the vent back down and connect it to the horizontal sink drain immediately downstream of the vertical fixture drain using a wye‑branch. This is the required return vent configuration. § 909.1.
- If your return‑bend cannot be a single factory return, assemble 45° + 90° + 45° elbows in that order under the drainboard (permitted alternative). § 909.1.
- At the vertical vent immediately below the floor, install a wye to take off the foot vent. Route the foot vent either:
- Option A: horizontally to the nearest partition, then vertically through the roof to open air; or
- Option B: tie into another vent at a point ≥ 6 inches (152 mm) above the sink flood‑level rim. § 909.1.
- On the portion of the vent below the floor, use drainage fittings and slope the run at least 1/4 inch per foot back toward the island sink drain. For example, a 4‑ft below‑floor run must drop at least 1 inch back to the drain. § 909.1.
- Install an accessible cleanout in the vertical portion of the foot vent (inside the island or immediately above the accessible panel) so the foot vent can be rodded. § 909.1.
Check sizing: choose vent pipe diameter per the code’s vent sizing tables (the island vent’s diameter “shall be as elsewhere required in this code” — use applicable fixture unit totals and Table/sections for sizing). § 909.1.
Related provisions
- § 908.0 — Wet venting (general limits and sizing rules that may interact with island vent decisions).
- § 905.3 — Vent pipe rise / height above fixture considerations (see Chapter 9 vent requirements).
- § 904.0 — Vent sizing provisions and minimum vent size rules (general vent sizing referenced by § 909.1).
- § 910.0 — Combination waste and vent systems (alternative systems and approval language).
- § 1002.4 — Opening location for trap/vent openings (general trap/vent rules referenced elsewhere in Chapter 10).
If you need the exact vent‑sizing table values or trap arm length limits, those are located in the other sections referenced above; § 909.1 defers sizing to “elsewhere required in this code.”
Code references
Grounded in the retrieved California Plumbing Code — click a citation to read the verbatim passage:
CPC § 908.2.4 High 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 § 904.0. High relevance — show source text
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.
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
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 § 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 § 420.0 High relevance — show source text
SINKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .420.0
Approved standards . . . . . . . . . . . . . . . . . . . . . . .420.1 Clinical . . . . . . . . . . . . . . . . . . . . . .205.0, 413.1, 1303.7
Floor . . . . . . . . . . . . . . . . . . . . . . . . . . . . .421.0, B 101.2
Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .909.1
Laundry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .420.4 Prohibited types . . . . . . . . . . . . . . . . . . . .405.3, B 101.2
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .420.4
Special use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .406.2 Three-compartment . . . . . . . . . . . . . . . . . . . . . . .1001.2
SIZE OF
Building sewers . . . . . . . . . . . .703.2, 717.0, Table 717.1 Cesspools . . . . . . . . . . . . . . . . . . . . . . . . . .Appendix H Chimneys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .509.5.5 Circuit venting . . . . . . . . . . . . . . . . . . . . . . . . . . . . .911.0
Combination waste
and vent piping . . . . . . . . . . . . . . . . .910.0, Appendix B Combustion air openings . . . . . . . . . . . . .506.3 – 506.5 Condensate pipe . . . . . . . . . . . . . . . .814.3, Table 814.3 Disposal fields . . . . . . . . . . . . . . . . . . . . . . .Appendix H Drainage piping . . . . . . . . . . . . . . . .Table 702.1, 703.0, Table 703.2, C 304.0,
E 302.2, E 504.4
FOG disposal systems . . . . . . . . . . . . . . . . . . . . .1015.3
Fuel gas piping systems . . . . . .1208.3, 1214.0, 1215.0,
E 403.2, Table E 403.2
Fuel gas vents . . . . . . . . . . . . . . . . . . .509.6.2, 509.7.4,
CPC § 2025 High 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.
2025 CALIFORNIA PLUMBING CODE xv
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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 § 1017.0 Medium relevance — show source text
Oil and flammable liquid . . . . . . . . . . . . . . . . . . . .1017.0 Packing establishments . . . . . . . . . . . . . . . . . . . .1010.0
Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1016.0
Slaughterhouses . . . . . . . . . . . . . . . . . . . . . . . . .1010.0
Vents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .902.1
INTERMIXING OF
METALS PROHIBITED . . . . . . . . . . . . . . . . .310.6, 604.1
INVERT, DEFINITION . . . . . . . . . . . . . . . . . . . . . . . . . .211.0
IRON PIPE SIZE (IPS) PIPE . . . . . . . . . . . . . . . . . . . .302.0
IRRIGATION FIELD
Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . .1504.5
Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .211.0
Gray water systems . . . . . . . . . . . . . .1504.5 – 1504.5.1
Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . .1504.4
Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1504.5.2
Size . . . . . . . . . . . . . . . . .1504.2, Table 1504.2, 1504.3
Soil type . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 1504.2
Subsoil construction . . . . . . . . . . . . . . . .Table 1504. 5.3
Valved zones. . . . . . . . . . . . . . . . . . . . . . . . . . . .1504.1
ISLAND FIXTURE, VENTING . . . . . . . . . . . . . . . . . . .909.0
– J –
JOINTS AND
CONNECTIONS . . . . . . . . . . . . . . . .315.0, 605.0, 705.0,
1208.5.10 – 1208.5.12.5,
1320.0
ABS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .705.1
Asbestos cement pipe . . . . . . . . . . . . .Table 510.1.2(5), Table 510.2(5)
CPC § 710.11 Medium relevance — show source text
Where the preceding requirements are met and the vent, after leaving the sump, is combined with vents from fixtures discharging into the sump, the size of the combined vent need not exceed that required for the total number of fixtures discharging into the sump. No vent from an air-operating sewage ejector shall combine with other vents. 710.11 Air Tanks. Air tanks shall be so proportioned as to be of equal cubical capacity to the ejectors connected in addition to that in which there shall be maintained an air pressure of not less than 2 pounds per foot (lb/ft) (3 kg/m) of height the sewage is to be raised. No water-operated ejectors shall be permitted. 710.12 Grinder Pump Ejector. Grinder pumps shall be permitted to be used. 710.12.1 Discharge Piping. The discharge piping shall be sized in accordance with the manufacturer’s installation instructions and shall be not less than 1 [1] ⁄ 4 inches (32 mm) in diameter. A check valve and fullwaytype shutoff valve shall be located on the discharge line. 710.13 Macerating Toilet Systems and Pumped Waste Systems. Fixtures shall be permitted to discharge to a macerating toilet system, or pumped waste system shall be permitted as an alternate to a sewage pump system where approved by the Authority Having Jurisdiction. Such systems shall comply with ASME A112.3.4/CSA B45.9 and shall be installed in accordance with the manufacturer’s installation
instructions.
710.13.1 Sumps. The sump shall be watertight and gastight. 710.13.2 Discharge Piping. The discharge piping shall be sized in accordance with manufacturer’s instructions and shall be not less than [3] ⁄ 4 of an inch (20 mm) in diameter. The developed length of the discharge piping shall not exceed the manufacturer’s instructions. A check
174 2025 CALIFORNIA PLUMBING CODE
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SANITARY DRAINAGE
valve and fullway-type shutoff valve shall be located within the discharge line or internally within the device.
710.13.3 Venting. The plumbing fixtures that discharge into the macerating device shall be vented in accordance with this code. The sump shall be vented in accordance with the manufacturer’s instructions, and such vent shall be permitted to connect to the fixture venting.
711.0 Suds Relief.
711.1 General. Drainage connections shall not be made into a drainage piping system within 8 feet (2438 mm) of a vertical to horizontal change of direction of a stack containing suds-producing fixtures. Bathtubs, laundries, washing machine standpipes, kitchen sinks, and dishwashers shall be considered suds-producing fixtures. Where parallel vent stacks are required, they shall connect to the drainage stack at a point 8 feet (2438 mm) above the lowest point of the drainage stack.
Exceptions:
(1) Single-family residences.
(2) Stacks receiving the discharge from less than three stories of plumbing fixtures.
712.0 Testing.
CPC § 908.1 Medium relevance — show source text
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
911.3 Relief Vent . . . . . . . . . . . . . . . . . .192
911.4 Slope and Size of Horizontal Branch . . . . . . . . . . . . . . . . . . . . .192
911.5 Additional Fixtures . . . . . . . . . . . .192
912.0 Engineered Vent System . . . . . . .192
912.1 General . . . . . . . . . . . . . . . . . . . . .192
912.2 Minimum Requirements . . . . . . . .192
CHAPTER 10 TRAPS AND
INTERCEPTORS . . . . . . . . . . . . .193
1001.0 General . . . . . . . . . . . . . . . . . . . . .195
1001.1 Applicability . . . . . . . . . . . . . . . . . .195
1001.2 Where Required . . . . . . . . . . . . . .195
1002.0 Traps Protected by Vent Pipes . .195
1002.1 Vent Pipes . . . . . . . . . . . . . . . . . .195
1002.2 Fixture Traps . . . . . . . . . . . . . . . .195
1002.3 Change of Direction . . . . . . . . . . .195
1002.4 Vent Pipe Opening . . . . . . . . . . . .195
1003.0 Traps – Described . . . . . . . . . . . .195
1003.1 General Requirements . . . . . . . . .195
CPC § 422.1 Medium relevance — show source text
1
422.1 Exception
Table 422.1
422.1.1
422.1.3
422.1.4
422.2
422.2 Exceptions
422.2 Exception (4)
422.3.1 & Exception
422.4
422.5
422.6_Exception (3)
422.7_Exception (2)
422.8
422.9
422.10
422.11
Table 4-1
Table 4-2
Table 4-3
Table 4-4|||||||||||||||||||X|||||| |Adopting Agency
Adopt Entire Chapter
Adopt Entire Chapter as
amended (amended
sections listed below)
Adopt only those sections
that are listed below
Chapter/Section
422.1
422.1 Exception
Table 422.1
422.1.1
422.1.3
422.1.4
422.2
422.2 Exceptions
422.2 Exception (4)
422.3.1 & Exception
422.4
422.5
422.6_Exception (3)
422.7_Exception (2)
422.8
422.9
422.10
422.11
Table 4-1
Table 4-2
Table 4-3
Table 4-4||||||||||||||||||X|||||||This state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.
58 2025 CALIFORNIA PLUMBING CODE
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
CHAPTER 4
PLUMBING FIXTURES AND FIXTURE FITTINGS
Note: In addition to the requirements of this chapter, buildings or facilities where accessibility is required for applications listed in California Code of Regulations, Title 24, Part 2 (California Building Code), Chapter 1, Section 1.9.1 regulated by the Division of the State Architect–Access Compliance shall also comply with Title 24, Part 2, Chapter 11A or 11B, as applicable under authority cited by CA Government Code Section 4450 and in reference cited by CA Government Code Sections 4450 through 4461, 12955.1(c), and CA Health and Safety Code Sections 18949.1, 19952 through 19959.
401.0 General.
401.1 Applicability. This chapter shall govern the materials and installation of plumbing fixtures, including faucets and fixture fittings, and the minimum number of plumbing fixtures required based on occupancy. 401.2 Quality of Fixtures. Plumbing fixtures shall be constructed of dense, durable, non-absorbent materials and shall have smooth, impervious surfaces, free from unnecessary concealed fouling surfaces. _**401.3 Water-Conserving Fixtures and Fittings.
CPC § 110.10 Medium relevance — show source text
Install alternative plumbing piping to permit the discharge from the clothes washer and all showers and bathtubs to be used for an irrigation system in compliance with the California Plumbing Code and any applicable local ordinances; or iv. Install a rainwater catchment system designed to comply with the California Plumbing Code and any applicable local ordinances, and that uses rainwater flowing from at least 65 percent of the available roof area.
B. Multifamily buildings, hotel/motel occupancies and nonresidential buildings. The solar zone shall be located on the roof or overhang of the building or on the roof or overhang of another structure located within 250 feet of the building or on covered parking installed with the building project, and shall have a total area no less than 15 percent of the total roof area of the building excluding any skylight area. The solar zone requirement is applicable to the entire building, including mixed occupancy.
Exception 1 to Section 110.10(b)1B: High-rise multifamily buildings, hotel/motel occupancies, and nonresidential buildings with a permanently installed solar electric system having a nameplate DC power rating, measured under Standard Test Conditions, of no less than one watt per square foot of roof area.
2025 CALIFORNIA ENERGY CODE 61
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
ALL OCCUPANCIES—MANDATORY REQUIREMENTS FOR THE MANUFACTURE, CONSTRUCTION AND INSTALLATION OF SYSTEMS, EQUIPMENT AND BUILDING COMPONENTS
Exception 2 to Section 110.10(b)1B: High-rise multifamily buildings, hotel/motel occupancies with a permanently installed domestic solar water-heating system complying with Section 150.1(c)8Biii.
Exception 3 to Section 110.10(b)1B: Buildings with a designated solar zone area that is no less than 50 percent of the potential solar zone area. The potential solar zone area is the total area of any low-sloped roofs where the annual solar access is 70 percent or greater and any steep-sloped roofs oriented between 90 degrees and 300 degrees of true north where the annual solar access is 70 percent or greater. Solar access is the ratio of solar insolation including shade to the solar insolation without shade. Shading from obstructions located on the roof or any other part of the building shall not be included in the determination of annual solar access.
Exception 4 to Section 110.10(b)1B: Low-rise and high-rise multifamily buildings with all thermostats in each dwelling unit are demand response controls that comply with Section 110.12(a), and are capable of receiving and responding to Demand Response Signals prior to granting of an occupancy permit by the enforcing agency. In addition, either A or B below:
A. In each dwelling unit, comply with one of the following measures: i. Install a dishwasher that meets or exceeds the ENERGY STAR Program requirements with either a refrigerator that meets or exceeds the ENERGY STAR Program requirements or a whole house fan driven by an electronically commutated motor; or ii. Install a home automation system that complies with Section 110.12(a) and is capable of, at a minimum, controlling the appliances and lighting of the dwelling and responding to demand response signals; or iii. Install alternative plumbing piping to permit the discharge from the clothes washer and all showers and bathtubs to be used for an irrigation system in compliance with the California Plumbing Code and any applicable local ordinances; or iv.
CPC § 1323.13.3 Medium relevance — show source text
2, 1323.13.3| |1326.4 - 1326.10|1326.5 - 1326.11| |1505.6 - 1505.14|1505.5 - 1505.13| |Figure 1505.10|Figure 1505.9| |1506.6 - 1506.13|1506.5 - 1506.12| |1603.3 - 1603.4|1603.4 - 1603.5| |Table 1603.4|Table 1603.5| |1603.5 - 1603.19|1603.6 - 1603.20| |1603.20|1503.2.4| |L 402.9 - L 402.11|L 402.8 - L 402.10| |L 404.9 - L 404.12|L 404.8 - L 404.11| |L 411.5, L 411.6|L 411.2, L411.3| |L 411.7|L 411.4| |L 411.9 - L 411.12|L 411.5 - L 411.8|
xxii 2025 CALIFORNIA PLUMBING CODE
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Uniform Plumbing Code – 2024 Edition:
The Uniform Plumbing Code is the most widely adopted plumbing code in the world. The 2024 edition contains complete “turnkey” requirements for the installation and maintenance of plumbing systems, all in one easy to use book.
Uniform Plumbing Code Illustrated Training Manual:
The UPC Illustrated Training Manual is an excellent reference for anyone involved in the plumbing industry. It contains an extensive definitions section and several hundred comprehensive technical diagrams and illustrations. It serves as a textbook, and it also is useful as a valuable tool for explaining the intent and use of the Code.
Uniform Plumbing Code Study Guide:
This book is the perfect complement to the UPC Illustrated Training Manual. Alone, it constitutes a complete self-study course for learning the UPC. It has hundreds of questions, general practice exams, and plumbing math, pipe sizing exercises and fitting identification. A big help in getting you ready for a certification exam!
Guide to Important Code Questions to the Uniform Plumbing Code:
An excellent reference for learning and understanding plumbing code changes and identifies code changes between editions. It is a useful tool for preparing code change proposals.
Uniform Mechanical Code – 2024 Edition:
The Uniform Mechanical Code contains complete requirements for the installation and maintenance of heating, ventilating, cooking and refrigeration systems.
Uniform Mechanical Code Illustrated Training Manual:
Contains technical diagrams and illustrations that demonstrate the intent and use of the UMC. A great reference for everyone involved in Mechanical HVACR design and installation.
Uniform Mechanical Code Study Guide:
Frequently asked questions
Can the island sink’s return vent be smaller than the rest of the building vent?
No. § 909.1 states that “pipe sizing shall be as elsewhere required in this code,” so use the standard vent‑sizing rules for the fixture unit load rather than reducing size just because it’s an island installation.
Where must the foot vent tie into other vents if I don’t run it to the roof?
If you tie the foot vent into other vents, the connection point must be not less than 6 inches (152 mm) above the flood‑level rim of the fixtures served, per § 909.1.
Is an accessible cleanout required?
Yes — § 909.1 requires an accessible cleanout in the vertical portion of the foot vent.
Can the island sink drain serve other fixtures upstream of the returned vent?
No. The code explicitly says the island sink drain upstream of the returned vent shall serve no other fixtures. § 909.1.
What slope is required for the vent run below the floor?
The vent run below the floor must use drainage fittings and maintain a slope of not less than 1/4 inch per foot (20.8 mm/m) back to the drain. § 909.1.
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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