CPC · California Plumbing Code

Trap seal primer devices: standards and compliance

Q: What is the single standard I must check when buying a potable water trap primer?

Check that the unit is listed to ASSE 1018 , per § 1007.2 . Also verify the label and manufacturer literature match the certification.

Q: Do drain‑type primers have a water‑use limit?

Drainage‑type trap seal primer devices are not limited in the amount of water they discharge per the Appendix (see L 412.2), but water‑supplied electronic/pressure primers may be limited under Appendix L to 30 gallons/year per drain where Appendix L is enforced.

Q: If I install a trap primer, does it still need to be accessible?

Yes — the CPC requires trap primers to be accessible for maintenance (cleaning, adjustments, replacement) under § 1007.1 .

If a floor drain or other rarely used trap might evaporate, the CPC says install a trap primer that meets the listed standard: potable water primers must be ASSE 1018; drainage or electronic types must meet ASSE 1044 or IAPMO PS 76. The primer must be accessible for maintenance and, where Appendix L applies, water‑supplied primers are limited to 30 gallons/year per drain.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

The California Plumbing Code requires that floor drains and similar traps that are directly connected to the drainage system and subject to infrequent use be protected with a trap seal primer and that the primer be accessible for maintenance — § 1007.1. The CPC then requires that potable water‑supply trap seal primer valves comply with ASSE 1018, and that drainage‑type or electronic design trap seal primer devices comply with ASSE 1044 or IAPMO PS 76 — § 1007.2.

The single most important rule: Where a remote trap (for example, a rarely used floor drain) is at risk of losing its water seal, provide a trap primer that meets the required certification standard and keep it accessible for maintenance.

Requirements in detail

When a trap primer is required

Trap primer required: Floor drains or similar traps that are directly connected to the drainage system and subject to infrequent use shall be protected with a trap seal primer, unless the Authority Having Jurisdiction (AHJ) finds it unnecessary. Maintenance access is required. § 1007.1.

What standard the device must meet

Potable water supply primer valves — must comply with ASSE 1018. § 1007.2.
Drainage‑type or electronic design trap seal primer devices — must comply with ASSE 1044 or IAPMO PS 76. § 1007.2.

Accessibility & maintenance

Trap primers must be accessible for maintenance (cleaning, adjustment, replacement). See the requirement that primers be accessible. § 1007.1.

Water‑use / efficiency note (Appendix L)

Where the Appendix L (conservation) applies, water‑supplied trap primers (electronic or pressure‑activated) are limited to not more than 30 gallons per year per drain. This is an Appendix L provision and applies where Appendix L is enforced. L 412.1.

Decision‑relevant quick reference table

Decision dimension	Required value / rule	Code Reference
When required	Floor drains/similar traps subject to infrequent use (AHJ may waive)	§ 1007.1
Potable water supply primer standard	ASSE 1018	§ 1007.2
Drainage or electronic type primer standard	ASSE 1044 or IAPMO PS 76	§ 1007.2
Accessibility	Must be accessible for maintenance	§ 1007.1
Water use limit (where Appendix L applies)	≤ 30 gallons/year per drain for electronic/pressure‑activated water primers	L 412.1 (Appendix L)
Flushometer tailpiece primers	Allowed when in accordance with ASSE 1044 or IAPMO PS 76 (explicit exception)	Appendix / L notes (see exception)

Exceptions & special cases

AHJ exception: The Authority Having Jurisdiction may determine a trap primer is not necessary for safety or sanitation for a specific trap — § 1007.1. If the AHJ accepts an alternate, document that determination.
Flushometer tailpiece primers: the code notes an exception that flushometer tailpiece trap primers are acceptable in accordance with ASSE 1044 or IAPMO PS 76. See the Appendix/notes.
Water‑use limit: The 30 gallons/year per drain restriction applies where Appendix L (water conservation provisions) is adopted/enforced; it is not a universal requirement in the mandatory code text but can be locally applicable. L 412.1.

Common mistakes

Installing a primer that is not certified to the required standard (e.g., using a non‑listed potable‑water primer instead of ASSE 1018 or using an uncertified drainage/electronic unit). Check the device label and spec sheet against § 1007.2.
Ignoring AHJ consultation: assuming every floor drain must have a primer without checking whether the AHJ will waive the requirement per § 1007.1.
Poor access: locating the primer where routine maintenance or replacement is impractical — primers must be accessible for maintenance under § 1007.1.
Overlooking water‑use limits: where Appendix L applies, selecting a water‑supplied primer that exceeds 30 gallons/year per drain. Confirm applicability of Appendix L to your project. L 412.1.

Worked example — concrete scenario with numbers

Scenario: A commercial building has a rarely used basement floor drain. The designer chooses a potable‑water‑supplied trap primer valve.

Steps and compliance checks:

Confirm the drain is "subject to infrequent use" so a primer is appropriate (or check with AHJ if waiver is expected) — § 1007.1.
Select a primer valve listed to ASSE 1018 (potable water supply primer valves must meet ASSE 1018) — § 1007.2. Verify the manufacturer’s data sheet and label show ASSE 1018 certification.
Provide service access so the valve is reachable without destructive work — accessibility required by § 1007.1.
If Appendix L applies at the project (water conservation enforced), confirm the chosen electronic/pressure‑activated water‑supplied primer will use ≤ 30 gallons per year per drain. Example math: if the primer dispenses 0.25 gallon per activation, allowable activations = 30 ÷ 0.25 = 120 activations per year, or about once every 3 days on average. If the device cycles more often than that, choose a lower‑volume primer or a drainage‑type primer that is not limited by Appendix L. L 412.1.

Related provisions

§ 1007.1 — Trap seal protection: when primers are required and accessibility for maintenance.
§ 1005.1 — Trap seal depth (minimum 2 in to maximum 4 in) — relevant to the trap the primer protects.
§ 1004.2 — Prohibited movable parts as traps (reminder: traps themselves cannot depend on movable parts).
Definitions — § 222.0 — Definitions for Trap Primer, Trap Seal, etc., used to interpret requirements.
L 412.1 (Appendix L) — Water use limits for water‑supplied trap primers (≤ 30 gallons/year per drain) where Appendix L is adopted.
Referenced standards list (Table 1701.1) — shows ASSE 1018 and ASSE 1044 cited for § 1007.2.

Code references

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

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

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

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

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

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

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

1009.0 Interceptors (Clarifiers) and Separators.

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

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

TABLE 1009.1 APPROVED INTERCEPTORS (CLARIFIERS)

CPC § 1007.2 High relevance — show source text

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

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

1009.0 Interceptors (Clarifiers) and Separators.

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

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

TABLE 1009.1 APPROVED INTERCEPTORS (CLARIFIERS)

APPLICATION	STANDARD
Fats, Oil, Grease (FOG)	ASME A112.14.3, ASME A112.14.4, ASME A112.14.6, CSA B481, ANSI/CAN/IAPMO Z1001, PDI G-101, PDI G-102
Solid Waste	IAPMO IGC 167
Non-petroleum Oil	ASME A112.14.6, IAPMO PS 80, PDI G-102
Petroleum Oil	ASTM D6104, IAPMO IGC 183, IAPMO IGC 325

1009.2 Approval. The size, type, and location of each interceptor (clarifier) or separator shall be approved by the Authority Having Jurisdiction. Except where otherwise specifically permitted, no wastes other than those requiring treatment or separation shall be discharged into an interceptor (clarifier). 1009.3 Design. Interceptors (clarifiers) for sand and similar heavy solids shall be so designed and located as to be readily accessible for cleaning and shall have a water seal of not less than 6 inches (152 mm). 1009.4 Relief Vent. Interceptors (clarifiers) shall be so designed that they will not become air-bound where closed covers are used. Each interceptor (clarifier) shall be properly vented.

CPC § 408.4.2 High relevance — show source text
4, 408.4.2(1)| |ASSE 1018-2001 (R2021)|Trap Seal Primer Valves - Potable Water Supplied|Valves|1007.2| |ASSE 1019-2011 (R2016)|Wall Hydrant with Backflow Protection and Freeze Resistance|Backflow Protection|Table 603.2| |ASSE 1020-2020|Pressure Vacuum Breaker Assemblies|Backflow Protection|Table 603.2| |ASSE 1022-2021|Backflow Preventer for Beverage Dispensing Equipment|Backflow Protection|Table 603.2,
603.5.12| |ASSE 1023-2020|Electrically Heated or Cooled Water Dispensers|Appliances|417.6| |ASSE 1024-2017 (R2021)|Dual Check Backflow Preventers|Backflow Protection|Table 603.2, 603.5.12| |ASSE 1032-2004 (R2021)|Dual Check Valve Type Backflow Preventers for Carbonated
Beverage Dispensers, Post Mix Type|Backflow Protection|603.5.12| |ASSE 1035-2020|Laboratory Faucet Backflow Preventers|Backflow Protection|Table 603.2,
603.3.11| |ASSE 1037-2020/ASME
A112.1037-2020/CSA
B125.37-2020|Pressurized Flushing Devices for Plumbing Fixtures|Backflow Protection|413.2| |ASSE 1044-2015 (R2020)|Trap Seal Primer - Drainage Types and Electric Design Types|DWV Components|1007.2| |ASSE 1047-2021|Reduced Pressure Detector Backflow Prevention Assemblies|Backflow Protection|Table 603.2| |ASSE 1048-2021|Double Check Detector Backflow Prevention Assemblies|Backflow Protection|Table 603.2| |ASSE 1052-2016|Hose Connection Backflow Preventers|Backflow Protection|Table 603.2| |ASSE 1053-2019|Dual Check Backflow Preventer Wall Hydrants – Freeze
Resistant Type|Backflow Protection|Table 603.2| |ANSI/CAN/ASSE/IAPMO
1055-2020|Chemical Dispensers with Integral Backflow Protection|Backflow Protection|Table 603.2,
603.5.22(1)| |ASSE 1056-2013 (R2021)|Spill Resistant Vacuum Breaker Assemblies|Backflow Protection|Table 603.2| |ASSE 1057-2012|Freeze Resistant Sanitary Yard Hydrants with Backflow Pro-
tection|Backflow Protection|Table 603.2| |ASSE 1060-2017|Outdoor Enclosures for Fluid Conveying Components with
Errata dated February 1, 2019|Miscellaneous|603.4.7| |ASSE 1061-2020|Push-Fit Fittings|Fittings|Table 604.1,
605.1.3.3, 605.2.1.1,
605.3.2.1, 605.9.3| |ASSE 1062-2017 (R2021)|Temperature Actuated, Flow Reduction (TAFR) Valves for
Individual Supply Fittings|Valves|408.4.3, 417.
CPC § 25.4 High relevance — show source text
For SI units: 1 inch = 25.4 mm

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

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TRAPS AND INTERCEPTORS

1004.0 Traps.

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

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

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

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

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

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

CPC § 603.2 High relevance — show source text

2025 CALIFORNIA PLUMBING CODE 337

REFERENCED STANDARDS

TABLE 1701.1 (continued) REFERENCED STANDARDS

STANDARD NUMBER	STANDARD TITLE	APPLICATION	REFERENCED SECTION
ASSE 1012-2009	Backflow Preventers with an Intermediate Atmospheric Vent	Backflow Protection	Table 603.2
ASSE 1013-2021	Reduced Pressure Principle Backflow Prevention Assemblies	Backflow Protection	Table 603.2
ASSE 1014-2020	Backflow Prevention Devices for Hand-Held Showers	Backflow Protection	417.3
ASSE 1015-2021	Double Check Backflow Prevention	Backflow Protection	Table 603.2
ASSE 1016-2017/ASME A112.1016-2017/CSA B125.16-2017	Automatic Compensating Valves for Individual Showers and Tub/Shower Combinations	Valves	408.4, 408.4.2(1)
ASSE 1018-2001 (R2021)	Trap Seal Primer Valves - Potable Water Supplied	Valves	1007.2
ASSE 1019-2011 (R2016)	Wall Hydrant with Backflow Protection and Freeze Resistance	Backflow Protection	Table 603.2
ASSE 1020-2020	Pressure Vacuum Breaker Assemblies	Backflow Protection	Table 603.2
ASSE 1022-2021	Backflow Preventer for Beverage Dispensing Equipment	Backflow Protection	Table 603.2, 603.5.12
ASSE 1023-2020	Electrically Heated or Cooled Water Dispensers	Appliances	417.6
ASSE 1024-2017 (R2021)	Dual Check Backflow Preventers	Backflow Protection	Table 603.2, 603.5.12
ASSE 1032-2004 (R2021)	Dual Check Valve Type Backflow Preventers for Carbonated Beverage Dispensers, Post Mix Type	Backflow Protection	603.5.12
ASSE 1035-2020	Laboratory Faucet Backflow Preventers	Backflow Protection	Table 603.2, 603.3.11
ASSE 1037-2020/ASME A112.1037-2020/CSA B125.37-2020	Pressurized Flushing Devices for Plumbing Fixtures	Backflow Protection	413.2
ASSE 1044-2015 (R2020)	Trap Seal Primer - Drainage Types and Electric Design Types	DWV Components	1007.

CPC § 1003.2 Medium relevance — show source text
1003.2 Slip Joint Fittings . . . . . . . . . . . . .195

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Table 1009.1 Approved Interceptors (Clarifiers) . .196

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

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

2025 CALIFORNIA PLUMBING CODE xxxvii

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TABLE OF CONTENTS

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

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

1009.6 Maintenance of Interceptors . . . . .196

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

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

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

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

1010.3 Collection Centers and

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

1010.4 Horse Meat and Pet Food
CPC § 223.0 Medium relevance — show source text
Trap Arm. Those portions of a fixture drain between a trap and the vent.

Trap Primer. A device and system of piping that maintains a water seal in a remote trap. Trap Seal. The vertical distance between the crown weir and the top dip of the trap. Crown Weir (Trap Weir). The lowest point in the cross-section of the horizontal waterway at the exit of the trap. Top Dip (of the trap). The highest point in the internal cross-section of the trap at the lowest part of the bend (inverted siphon). By contrast, the bottom dip is the lowest point in the internal cross-section. Treated Gray Water. [BSC-CG & HCD 1] Nonpotable water meeting the definition of “gray water” collected and treated on-site suitable for direct beneficial use.

223.0 – U –

UPC. [HCD 1] “UPC” is the latest edition of the Uniform Plumbing Code, published by the International Association of Plumbing and Mechanical Officials. Unsanitary. See Insanitary.

User Outlet. See Station Outlet.

2025 CALIFORNIA PLUMBING CODE 43

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DEFINITIONS

224.0 – V –

Vacuum. A pressure less than that exerted by the atmosphere.

Vacuum Breaker. See Backflow Preventer.

Vacuum Relief Valve. A device that prevents excessive vacuum in a pressure vessel. Vacuum System-Level 1. A system consisting of central vacuum-producing equipment with pressure and operating controls, shutoff valves, alarm warning systems, gauges, and a network of piping extending to and terminating with suitable station inlets at locations where patient suction could be required. Valve, Balancing. A valve that regulates and controls the return of water to the water heater in a recirculating hot water piping system. Valve, Isolation. A valve that isolates one piece of equipment from another.

Valve, Pressure-Relief. A pressure-actuated valve held closed by a spring or other means and designed automatically to relieve pressure in excess of its setting.

Valve, Riser. A valve at the base of a vertical riser that isolates that riser.

Valve, Service. A valve is serving horizontal piping extending from a riser to a station outlet or inlet. Valve, Source. A single valve at the source that controls a number of units that makes up the source. Valve, Zone. A valve that controls the gas or vacuum to a particular area. Vent. See Plumbing Vent; Dry Vent; Wet Vent. Vent Connector, Gas. That portion of a gas venting system that connects a listed gas appliance beginning at the draft hood or flue collar to a gas vent and is installed entirely within the space or area in which the appliance is located. Vent Offset. An arrangement of two or more fittings and pipe installed for the purpose of locating a vertical section of vent pipe in a different but parallel plane with respect to an adjacent section of vertical vent pipe. [NFPA 54:3.3.101] Vent Pipe. See Plumbing Vent. **Vent Stack.
CPC § 2.9 Medium relevance — show source text
[MP] TRAP. A fitting, either separate or built into a fixture, that provides a liquid seal to prevent the emission of sewer gases without materially affecting the flow of sewage or wastewater through it.

[MP] TRAP ARM. That portion of a fixture drain between a trap weir and the vent fitting.

[MP] TRAP PRIMER. A device or system of piping to maintain a water seal in a trap, typically installed where infrequent use of the trap would result in evaporation of the trap seal, such as floor drains.

[MP] TRAP SEAL. The trap seal is the maximum vertical depth of liquid that a trap will retain, measured between the crown weir and the top of the dip of the trap.

[RB] TRIM. Picture molds, chair rails, baseboards, handrails, door and window frames, and similar decorative or protective materials used in fixed applications.

[RB] TRUSS DESIGN DRAWING. The graphic depiction of an individual truss, that describes the design and physical characteristics of the truss.

[RB] TUBULAR DAYLIGHTING DEVICE (TDD). A nonoperable fenestration unit primarily designed to transmit daylight from a roof surface to an interior ceiling via a tubular conduit. The basic unit consists of an exterior glazed weathering surface, a light-transmitting tube with a reflective interior surface, and an interior-sealing device such as a translucent ceiling panel. The unit may be factory assembled, or field assembled from a manufactured kit.

[MP] TYPE L VENT. A listed and labeled vent conforming to UL 641 for venting oil-burning appliances listed for use with Type L vents or with gas appliances listed for use with Type B vents.

[RB] TYPE X. A type of gypsum panel product with special core additives to increase the fire resistance as specified by the applicable standards listed in Section R702.3 (see the definition of “Gypsum panel product”).

[RB] UNDERLAYMENT. One or more layers of felt, sheathing paper, nonbituminous saturated felt, or other approved material over which a roof covering, with a slope of 2 units vertical in 12 units horizontal (17-percent slope) or greater, is applied.

[MP] VACUUM BREAKER. A device that prevents back-siphonage of water by admitting atmospheric pressure through ports to the discharge side of the device.

[RB] VAPOR DIFFUSION PORT. An assembly constructed or installed within a roof assembly at an opening in the roof deck to convey water vapor from an unvented attic to the outside atmosphere.

[RB] VAPOR PERMEABLE. The property of having a moisture vapor permeance rating of 5 perms (2.9 × 10 [-10] kg/Pa × s × m [2] ) or greater, where tested in accordance with Procedure A or Procedure B of ASTM E96. A vapor permeable material permits the passage of moisture vapor.

[RB] VAPOR RETARDER CLASS. A measure of the ability of a material or assembly to limit the amount of moisture that passes through that material or assembly. Vapor retarder class shall be defined using the desiccant method with Procedure A of ASTM E96 as follows:

Class I: ≤ 0.1 perm rating

Class II: > 0.1 to ≤ 1.0 perm rating

Class III: > 1.0 to ≤ 10 perm rating
CPC § 412.2 Medium relevance — show source text
Exception: Flushometer tailpiece trap primers in accordance with ASSE 1044 or IAPMO PS 76.

L 412.2 Drainage Type Trap Seal Primer Devices. Drainage type trap seal primer devices shall not be limited in the amount of water they discharge.

L 413.0 Vehicle Wash Facilities.

L 413.1 Automatic. The maximum make-up water use for automobile washing shall not exceed 40 gallons (151 L) per vehicle for in-bay automatic car washes and 35 gallons (132 L) for conveyor and express type car washes. L 413.2 Self-Service. Spray wands and foamy brushes shall use not more than 3.0 gpm (0.19 L/s). L 413.3 Reverse Osmosis. Spot-free reverse osmosis discharge (reject) water shall be recycled. L 413.4 Towel Ringers. Towel ringers shall have a positive shutoff valve. Spray nozzles shall be replaced annually.

Exception: Bus and large commercial vehicle washes are exempt from the requirements of this section.

L 501.0 Water Heating Design, Equipment, and Instal- lation.

L 501.1 Scope. The provisions of this section shall establish the means of conserving potable and nonpotable water and energy associated with the generation and use of hot water in a building. This includes provisions for the hot water distribution system, which is the portion of the potable water distribution system between a water heating device and the plumbing fixtures, including dedicated return piping and appurtenances to the water heating device in a recirculation system. L 501.2 Insulation. Hot water supply and return piping shall be thermally insulated. The wall thickness of the insulation shall be equal to the nominal diameter of the pipe up to 2 inches (50 mm). The wall thickness shall be not less than 2 inches (51 mm) for nominal pipe diameters exceeding 2 inches (50 mm). The conductivity of the insulation [k-factor (Btu•in/(h•ft [2] - °F))], measured radially, shall not be more than 0.28 [Btu•in/(h•ft [2] - °F)] [0.04 W/(m•K)]. Hot water piping to be insulated shall be installed such that insulation is continuous. Pipe insulation shall be installed to within [1] ⁄ 4 of an inch (6.4 mm) of appliances, appurtenances, fixtures, structural members, or a wall where the pipe passes through to connect to a fixture within 24 inches (610 mm).

2025 CALIFORNIA PLUMBING CODE 507

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APPENDIX L

Exceptions:

(1) Where the hot water pipe is installed in a wall that is not of a width to accommodate the pipe and insulation, the insulation thickness shall be permitted to have the maximum thickness that the wall is capable of accommodating and not less than [1] ⁄ 2 of an inch (12.7 mm) thick.

(2) Hot water supply piping exposed under sinks, lavatories, and similar fixtures.

L 501.2.1 Pipe Supports. Pipe supports shall be installed on the outside of the pipe insulation.
CPC § 222.0 Medium relevance — show source text
222.0 – T –

T Rating. The time period that the penetration firestop system, including the penetrating item, limits the maximum temperature rise of 325°F (181°C) above its initial temperature through the penetration on the nonfire side, where tested in accordance with ASTM E814 or UL 1479.

Tailpiece. The pipe or tubing that connects the outlet of a plumbing fixture to a trap. Testing Agency. [HCD 1] See “Approved Testing Agency”. Thermostatic (Temperature Control) Valve. A mixing valve that senses outlet temperature and compensates for fluctuations in incoming hot or cold water temperatures. Toilet. [OSHPD 1, 2, 3, 4 & 5] A fixture within a toilet room which is used for defecation or urination. Toilet Facility. A room or space containing not less than one lavatory and one water closet.

Toilet Room. [OSHPD 1, 2, 3, 4 & 5] A room within or on the premises containing water closets, urinals, and other required facilities. Transition Gas Riser. A listed or approved section or sections of pipe and fittings used to convey fuel gas and installed in a gas piping system to provide a transition from belowground to aboveground.

Trap. A fitting or device so designed and constructed as to provide, where properly vented, a liquid seal that will prevent the back passage of air without materially affecting the flow of sewage or wastewater through it.

Trap Arm. Those portions of a fixture drain between a trap and the vent.

Trap Primer. A device and system of piping that maintains a water seal in a remote trap. Trap Seal. The vertical distance between the crown weir and the top dip of the trap. Crown Weir (Trap Weir). The lowest point in the cross-section of the horizontal waterway at the exit of the trap. Top Dip (of the trap). The highest point in the internal cross-section of the trap at the lowest part of the bend (inverted siphon). By contrast, the bottom dip is the lowest point in the internal cross-section. Treated Gray Water. [BSC-CG & HCD 1] Nonpotable water meeting the definition of “gray water” collected and treated on-site suitable for direct beneficial use.

223.0 – U –

UPC. [HCD 1] “UPC” is the latest edition of the Uniform Plumbing Code, published by the International Association of Plumbing and Mechanical Officials. Unsanitary. See Insanitary.

User Outlet. See Station Outlet.

2025 CALIFORNIA PLUMBING CODE 43

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

DEFINITIONS

224.0 – V –

Vacuum. A pressure less than that exerted by the atmosphere.

Vacuum Breaker. See Backflow Preventer.
CPC § 1.8.7.3 Medium relevance — show source text
3. The local building department may require tests performed by an approved testing agency at the expense of the owner or owner’s agent as proof of compliance.

4. If the proposed alternate is related to accessi bil- ity in covered multifamily dwellings or facilities serving covered multifamily dwellings, as defined in Chapter 2 of the California Building Code, the proposed alternate must also meet the threshold set for equivalent facilitation as defined in Chapter 2 of the California Building Code.

For additional information regarding approval of alternates by a local building department pur- suant to the State Housing Law, see California Health and Safety Code Section 17951(e) and Cali- fornia Code of Regulations, Title 25, Division 1, Chapter 1, Subchapter 1.

1.8.7.3 Department of Housing and Community Devel- opment. The Department of Housing and Community Development may approve alternates for use in the erec- tion, construction, reconstruction, movement, enlarge- ment, conversion, alteration, repair, removal, or demolition of apartments, condominiums, hotels, motels, lodging houses, dwellings, or accessory structures thereto, and permanent buildings in mobilehome parks and special occupancy parks. The consideration and approval of alternates shall comply with the following:

1. The department may require tests at the expense of the owner or owner’s agent to substantiate compli- ance with the California Building Standards Code.

2. The approved alternate shall, for its intended pur- pose, be at least equivalent in performance and safety to the materials, designs, tests, or methods of construction prescribed by this code.

1.8.8 Appeals Board.

1.8.8.1 General. Every city, county, or city and county shall establish a process to hear and decide appeals of orders, decisions, and determinations made by the enforc- ing agency relative to the application and interpretation of this code and other regulations governing construction use, maintenance and change of occupancy. The govern- ing body of any city, county, or city and county may estab- lish a local appeals board and a housing appeals board to serve this purpose. Members of the appeals board(s) shall not be employees of the enforcing agency and shall be knowledgeable in the applicable building codes, reg- ulations and ordinances as determined by the governing body of the city, county, or city and county.

Where no such appeals boards or agencies have been established, the governing body of the city, county, or city and county shall serve as the local appeals board or housing appeals board as specified in California Health and Safety Code Sections 17920.5 and 17920.6.

1.8.8.2 Definitions. The following terms shall for the purposes of this section have the meaning shown.
CPC § 17.4 Medium relevance — show source text
8|17.4|1.5|2.5|3.4|5.1|0.6|1.0|1.3|1.9| |10|7.7|13.1|17.8|26.3|2.3|3.8|5.2|7.7|0.8|1.4|2.0|2.9| |12|10.8|18.4|24.9|NP|3.2|5.4|7.3|10.7|1.2|2.0|2.7|4.0| |14|14.4|24.5|NP|NP|4.2|7.1|9.6|14.3|1.6|2.7|3.6|5.4| |16|18.4|NP|NP|NP|5.4|9.1|12.4|18.3|2.0|3.4|4.7|6.9| |18|22.9|NP|NP|NP|6.7|11.4|15.4|22.7|2.5|4.3|5.8|8.6| |20|27.8|NP|NP|NP|8.1|13.8|18.7|27.6|3.1|5.2|7.0|10.4| |22|NP|NP|NP|NP|9.7|16.5|22.3|NP|3.7|6.2|8.4|12.4| |24|NP|NP|NP|NP|11.4|19.3|26.2|NP|4.3|7.3|9.9|14.6| |26|NP|NP|NP|NP|13.2|22.4|NP|NP|5.0|8.5|11.4|16.9| |28|NP|NP|NP|NP|15.1|25.7|NP|NP|5.7|9.7|13.1|19.4| |30|NP|NP|NP|NP|17.2|NP|NP|NP|6.5|11.0|14.9|22.0| |32|NP|NP|NP|NP|19.4|NP|NP|NP|7.3|12.4|16.8|24.8| |34|NP|NP|NP|NP|21.7|NP|NP|NP|8.2|13.9|18.8|NP| |36|NP|NP|NP|NP|24.1|NP|NP|NP|9.1|15.4|20.9|NP| |For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon per minute = 0.063 L/s, 1 pound per square inch = 6.895 kPa.
NP = Not Permitted. Pressure loss exceeds reasonable limits.
a. Values are applicable for underground piping materials listed in_ the California Plumbing Code_ and are based on an SDR of 11 and a Hazen Williams C Factor of 150.
b. Values include the following length allowances for fittings: 25-percent length increase for actual lengths up to 100 feet and 15-percent length increase for actual lengths over
100 feet.
c. Flow rate from Section P2904.4.2.

Frequently asked questions

What is the single standard I must check when buying a potable water trap primer?

Check that the unit is listed to ASSE 1018, per § 1007.2. Also verify the label and manufacturer literature match the certification.

Can I use an electronic primer instead of a water‑supplied primer?

Yes — electronic design type primer devices are allowed provided they comply with ASSE 1044 or IAPMO PS 76, per § 1007.2.

Do drain‑type primers have a water‑use limit?

Drainage‑type trap seal primer devices are not limited in the amount of water they discharge per the Appendix (see L 412.2), but water‑supplied electronic/pressure primers may be limited under Appendix L to 30 gallons/year per drain where Appendix L is enforced.

Who can waive the requirement for a trap primer?

The Authority Having Jurisdiction (AHJ) can determine a primer is not necessary for safety or sanitation under § 1007.1. Obtain written confirmation if you rely on a waiver.

If I install a trap primer, does it still need to be accessible?

Yes — the CPC requires trap primers to be accessible for maintenance (cleaning, adjustments, replacement) under § 1007.1.

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Related in the CPC

Required trap seal depth and protection

Floor drain and building trap special requirements

Trap seals, floor drains and primers

California Plumbing Code