CPC · California Plumbing Code

Required trap seal depth and protection

Q: How deep must a trap seal be?

Between 2 inches (51 mm) and 4 inches (102 mm) , unless the AHJ requires a deeper seal. § 1005.1

Q: When is a trap seal primer required?

A trap seal primer is required for floor drains or similar traps that are directly connected to the drainage system and subject to infrequent use , unless the AHJ determines it is unnecessary. § 1007.1

Q: Does the primer have to be serviceable?

Yes — trap seal primers shall be accessible for maintenance . § 1007.1

Q: Can I use a trap with movable parts or a bladder?

No — traps that depend on movable parts for the seal are prohibited (see trap requirements elsewhere in Chapter 10).

Q: What if my trap evaporates between uses?

If evaporation is a concern because the trap is infrequently used, install an accessible trap primer per § 1007.1 to maintain the required trap seal depth. § 1007.1

For homeowners: Plumbing code requires trap seals to hold between 2 and 4 inches of water to block sewer gas, and floor drains that sit unused must have a serviceable trap‑primer to keep that water from evaporating, unless the local inspector says otherwise.

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Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

Each fixture trap must provide a liquid trap seal of not less than 2 inches (51 mm) and not more than 4 inches (102 mm), unless a deeper seal is required by the Authority Having Jurisdiction. § 1005.1 .
Where floor drains or similar traps are directly connected to the drainage system and are subject to infrequent use, they shall be protected with a trap seal primer and the primer must be accessible for maintenance. § 1007.1 .

The trap seal must be between 2" and 4" (unless the AHJ requires deeper), and unused floor‑drain traps must have an accessible trap‑seal primer to keep that water seal from evaporating. § 1005.1 and § 1007.1

Requirements in detail

Key defined terms (first use bolded)

Trap — fitting providing a liquid seal to prevent sewer gas. § 1001.2 (definitions in CPC) .
Trap seal — the vertical distance between the crown (weir) and the top dip of the trap. See CPC definitions for the full term. .
Trap seal primer (trap primer) — a device/system that maintains a water seal in a trap (commonly used for floor drains). .
Authority Having Jurisdiction (AHJ) — the enforcing official that may require deviations (e.g., a deeper trap seal). § 1005.1 .

Quantitative requirements (decision‑relevant)

Item	Required value / trigger	Code Reference
Minimum trap seal depth	2 inches (51 mm)	§ 1005.1
Maximum trap seal depth	4 inches (102 mm) (unless AHJ requires deeper)	§ 1005.1
When a trap‑seal primer is required	Floor drains or similar traps that are directly connected and subject to infrequent use	§ 1007.1
Accessibility	Trap seal primers shall be accessible for maintenance	§ 1007.1

Notes:

The phrase “subject to infrequent use” in § 1007.1 governs when a primer is required; the AHJ can determine exceptions for safety or sanitation. § 1007.1 .
If the AHJ finds a deeper seal necessary, it may require one (this is the only code‑text path for seals deeper than 4"). § 1005.1 .

Practical installation guidance derived from the text

Set traps true (level/installed correctly) so the intended trap seal depth is achieved; protect traps from freezing where necessary. § 1005.1 .
For floor drains in rarely used spaces (mechanical rooms, infrequently occupied storage, etc.), plan for a trap primer that is accessible for routine servicing. § 1007.1 .

Exceptions & special cases

AHJ discretion: the AHJ may require a deeper trap seal than 4" for a particular installation — this is an exception explicitly allowed in § 1005.1. § 1005.1 .
AHJ exemption for primers: the AHJ may determine a trap seal primer is not necessary for safety or sanitation and therefore waive the requirement in § 1007.1. § 1007.1 .

Common mistakes

Installing a trap with less than 2" of seal (evaporation/siphon risk) — violates § 1005.1. § 1005.1 .
Using a trap seal deeper than 4" without AHJ approval — code limits depth to 4" unless AHJ requires deeper. § 1005.1 .
Failing to provide a trap primer for a floor drain that is infrequently used and directly connected to the drainage system. § 1007.1 .
Installing a primer that is inaccessible for maintenance (covers, buried valves, locked cabinets) — primers must be accessible. § 1007.1 .
Confusing trap seal depth with trap arm length or other venting dimensions — trap seal is a vertical depth between crown weir and top dip (see CPC definitions). .

Worked example — concrete scenario

Scenario: A new restaurant has a floor drain in a seldom-used dry-storage room. The plumbing contractor installs a standard trap.

Step 1 — trap seal depth: Install a trap that provides a liquid seal between 2" and 4". Choose a trap geometry with a measured trap seal of 3", which is within the required range. This satisfies § 1005.1. § 1005.1 .
Step 2 — decide on primer: Because the floor drain is directly connected to the building drainage and the room is infrequently used, a trap seal primer is required per § 1007.1. § 1007.1 .
Step 3 — accessibility and maintenance: Install the primer assembly in an accessable location (serviceable valve or accessible access panel) so it is “accessible for maintenance” per § 1007.1. § 1007.1 .
If the AHJ judged that the room is used frequently enough or that a primer would be a safety issue, they could waive the primer requirement — document any such determination. § 1007.1 .

Related provisions (select CPC sections)

§ 1005.1 — Trap seal depth and freezing protection (primary depth limits).
§ 1007.1 — Trap seal protection: primer requirement and accessibility.
§ 1007.2 — Standards for trap seal primer devices (referenced standards such as ASSE 1018, ASSE 1044, IAPMO PS 76). (See CPC referenced standards table for details.)
CPC definitions for Trap, Trap Seal, and Trap Primer (definitions clarify measurement/terminology).
Venting/trap protection pressure criterion (vent system trap seal protection to prevent >1 in. water column differential) — see venting requirements elsewhere in the CPC (e.g., vent system design).

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 § 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 § 911.3 High relevance — show source text
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

Table 1002.2 Horizontal Lengths of Trap Arms . . . . . . . . . . . . . . . . . . . . . . .195

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
CPC § 1.1 Medium relevance — show source text
1(2)_||||X||||||||||||||||||||| |903.1.1||||X|X|||||||||||||||||||| |903.1.2||||X||||||||||||||||||||| |903.1.3||||||||||X||X|X|X|X|||||||||| |906.2.1||||||||||X|X|X|X|X|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.

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188 2025 CALIFORNIA PLUMBING CODE

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CHAPTER 9

VENTS

901.0 General.

901.1 Applicability. This chapter shall govern the materials, design, and installation of plumbing vent systems. 901.2 Vents Required. Each plumbing fixture trap, except as otherwise provided in this code, shall be protected against siphonage and backpressure, and air circulation shall be ensured throughout all parts of the drainage system by means of vent pipes installed in accordance with the requirements of this chapter and as otherwise required by this code. 901.3 Trap Seal Protection. The vent system shall be designed to prevent a trap seal from being exposed to a pressure differential that exceeds 1 inch water column (0.24 kPa) on the outlet side of the trap.

902.0 Vents Not Required.

902.1 Interceptor. Vent piping shall be permitted to be omitted on an interceptor where such interceptor acts as a primary settling tank and discharges through a horizontal indirect waste pipe into a secondary interceptor. The second interceptor shall be properly trapped and vented. 902.2 Bars, Soda Fountains, and Counter. Traps serving sinks that are part of the equipment of bars, soda fountains, and counters need not be vented where the location and construction of such bars, soda fountains, and counters are such as to make it impossible to do so. Where such conditions exist, said sinks shall discharge using approved indirect waste pipes into a floor sink or other approved type of recep tor.

903.0 Materials.

903.1 Applicable Standards. Vent pipe and fittings shall comply with the applicable standards referenced in Table 701.2, except that:

(1) No galvanized steel or 304 stainless steel pipe shall be installed underground and shall be not less than 6 inches (152 mm) aboveground.

CPC § 3.1 Medium relevance — show source text

10|23/4| |F/C-6-RC-25|6″|6″ deep (4800 psi) concrete deck;1/4″ rein-
forcement bars at 71/2″ pitch with7/8″
cover;3/8″ main reinforcement bars at
31/2″ pitch perpendicular with7/8″ cover;
13′1″ span restrained.|195
psf|4 hrs|||7|1, 7|4| |F/C-6-RC-26|6″|6″ (4650 psi) concrete deck;1/4″ reinforce-
ment bars at 71/2″ pitch with7/8″ cover;3/8″
main reinforcement bars at 31/2″ pitch
perpendicular with1/2″ cover; 13′1″ span
restrained.|195
psf|2 hrs
23 min|||7|1, 2|21/4| |F/C-6-RC-27|6″|6″ deep (6050 psi) concrete deck;1/4″ rein-
forcement bars at 71/2″ pitch with7/8″
cover;3/8″ reinforcement bars at 31/2″
pitch perpendicular with1/2″ cover; 13′1″
span restrained.|195
psf|3 hrs
30 min|||7|1, 10|31/2| |F/C-6-RC-28|6″|6″ deep (5180 psi) concrete deck;1/4″ rein-
forcement bars at 8″ pitch with3/4″ cover;
1/4″ reinforcement bars at 51/2″ pitch
perpendicular with1/2″ cover; 13′1″ span
restrained.|150
psf|4 hrs|||7|1, 7|4|

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TABLE 3.1—continued FLOOR/CEILING ASSEMBLIES—REINFORCED CONCRETE	Col2	Col3	Col4	Col5	Col6	Col7	Col8	Col9	Col10
ITEM CODE	ASSEMBLY THICKNESS	CONSTRUCTION DETAILS	PERFORMANCE	PERFORMANCE	REFERENCE NUMBER	REFERENCE NUMBER	REFERENCE NUMBER	NOTES	REC. HOURS
ITEM CODE	ASSEMBLY THICKNESS	CONSTRUCTION DETAILS	LOAD	TIME	PRE-BMS-92	BMS-92	POST-BMS-92	POST-BMS-92	POST-BMS-92
F/C-6-RC-29	6″	6″ thick (4180 psi) concrete deck; 4″ × 3″ × 10 lbs R.S.J.; 2′6″ C.R.S.

CPC § 603.2 Medium 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

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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 § 501.6 Medium relevance — show source text
E 501.6 Floors and Drains. The floors shall be constructed of material impervious to water and shall be easily cleanable. A building having water-supplied water closets shall be provided with a floor drain in the toilet room. This drain shall be provided with means to protect the trap seal in accordance with this code.

E 501.7 Shower Size. Each shower, where provided, shall have a floor area of 36 inches by 36 inches (914 mm by 914 mm), shall be capable of encompassing a 30 inch (762 mm) diameter circle and shall be of the individual type. The shower area shall be visually screened from view with a minimum floor area of 36 by 36 inches (914 mm by 914 mm) per shower. Each shall be provided with individual dressing areas screened from view and shall contain a minimum of one clothing hook and stool (or bench area). E 501.7.1 Drainage Connection. Each shower area shall be designed to minimize the flow of water into the dressing area and shall be connected to the drainage system using a properly trapped and vented inlet. Each such area shall have an impervious, skid-resistant surface; wooden racks (duck boards) over shower floors shall be prohibited. E 501.8 Drinking Fountains. Where provided, drinking fountains shall be in accordance with the requirements of this code.

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APPENDIX E

E 502.0 Recreational Vehicle Park Potable Water Supply and Distribution. E 502.1 Quality. The supply or supplies of water shall comply with the potable water standards of the state, local health authority or, in the absence thereof, with the Drinking Water Standard of the Federal Environmental Protection Agency. E 502.2 Sources. Water approved by a regulating agency shall be acceptable. Where an approved public water supply system is available, it shall be used. Where the park has its own water supply system, the components of the system shall be approved. A water supply system that is used on a seasonal basis shall be provided with means for draining. E 502.3 Prohibited Connections. The potable water supply shall not be connected to a nonpotable or unapproved water supply, nor be subjected to backflow or backsiphonage. E 502.4 Supply. The water supply system shall be designed and constructed in accordance with the following:

(1) A minimum of 25 gallons (95 L) per day per site for sites without individual water connections.

(2) A minimum of 50 gallons (189 L) per day per site for sites with individual water connections.

(3) A minimum of 50 gallons (189 L) per day per site where water-supplied water closets are provided in restrooms.

E 502.5 Pressure and Volume. Where water is distributed under pressure to an individual site, the water supply system shall be designed to provide a minimum flow pressure of not less than 20 psi (138 kPa) with a minimum flow of 2 gallons per minute (gpm) (0.1 L/s) at an outlet. The pressure shall not exceed 80 psi (552 kPa).

CPC § 0.6 Medium relevance — show source text

D.|Column: 0.6″ minimum metal thickness;
protection: 11/2″ Portland cement plaster on
high ribbed metal lath,1/2″ broken air space.|—|3 hrs||1|||3| |C-11-CI-4|11″ O.D.|Column: 0.6″ minimum metal thickness;
protection: 2″ concrete other than siliceous
aggregate.|—|2 hrs
30 min||1|||21/2| |C-12-CI-5|12.5″
O.D.|Column: 7″ O.D. 0.6″ minimum metal thick-
ness; protection: 2″ porous hollow tile,3/4″
mortar between tile and column, outside
wire ties.|—|3 hrs||1|||3| |C-7-CI-6|7.6″ O.D.|Column: 7″ I.D.3/10″ minimum metal thick-
ness; concrete filled; unprotected.|—|30 min||1|||1/2| |C-8-CI-7|8.6″ O.D.|Column: 8″ I.D.3/10″ minimum metal thick-
ness; concrete filled reinforced with four
31/2″ ×3/8″ angles, in fill; unprotected
outside.|—|1 hr||1|||1|

For SI: 1 inch = 25.4 mm.

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NUMBER OF ASSEMBLIES

RESOURCE A—GUIDELINES ON FIRE RATINGS OF ARCHAIC MATERIALS AND ASSEMBLIES

FIGURE 2.3

STEEL COLUMNS—GYPSUM ENCASEMENTS

Col3	Col4	Col5	Col6	Col7	Col8	Col9	Col10	Col11	Col12	Col13	Col14	Col15	Col16	Col17


			11	11	11	11	12	12	12	12	12	12	12	12
			9	9	9	9	8	8	8	8	8	8	8	8
			5	5	10	10	6	6	6	6	6	6	6	6
1	1	3	2	2	7	7	4	4	4	13	13	13	13	13

0 1 2 3 4 5 6

7 8 9 10

FIRE-RESISTANCE RATING (HOURS)

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 § 6.98 Medium relevance — show source text
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CPC § 1001.0 Medium relevance — show source text
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CHAPTER 10

TRAPS AND INTERCEPTORS

1001.0 General.

1001.1 Applicability. This chapter shall govern the materials, design, and installation of traps and interceptors.

1001.2 Where Required. Each plumbing fixture shall be separately trapped by an approved type of liquid seal trap. This section shall not apply to fixtures with integral traps. Not more than one trap shall be permitted on a trap arm. Food waste disposers installed with a set of restaurant, commercial, or industrial sinks shall be connected to a separate trap.

Each domestic clothes washer and each laundry sink shall be connected to a separate and independent trap, except that a trap serving a laundry sink shall also be permitted to receive the waste from a clothes washer set adjacent to it.

The vertical distance between a fixture outlet and the trap weir shall be as short as practicable, but in no case shall the tailpiece exceed 24 inches (610 mm) in length.

One trap shall be permitted to serve a set of not more than three single compartment sinks or laundry sinks of the same depth or three lavatories immediately adjacent to each other and in the same room where the waste outlets are not more than 30 inches (762 mm) apart, and the trap is centrally located where three compartments are installed.

1002.0 Traps Protected by Vent Pipes.

1002.1 Vent Pipes. Each plumbing fixture trap, except as otherwise provided in this code, shall be protected against siphonage, backpressure, and air circulation shall be assured throughout the drainage system using a vent pipe installed in accordance with the requirements of this code.

1002.2 Fixture Traps. Each fixture trap shall have a protecting vent so located that the developed length of the trap arm from the trap weir to the inner edge of the vent shall be within the distance given in Table 1002.2 but in no case less than two times the diameter of the trap arm. 1002.3 Change of Direction. A trap arm shall be permitted to change direction without the use of a cleanout where such change of direction does not exceed 90 degrees (1.57 rad). Horizontal changes in the direction of trap arms shall be in accordance with Section 706.3.

Exception: For trap arms, 3 inches (80 mm) in diameter and larger, the change of direction shall not exceed 135 degrees (2.36 rad) without the use of a cleanout. 1002.4 Vent Pipe Opening. The vent pipe opening from soil or waste pipe, except for water closets and similar fixtures, shall not be below the weir of the trap.

1003.0 Traps – Described. 1003.1 General Requirements. Each trap, except for traps within an interceptor or similar device shall be selfcleaning. Traps for bathtubs, showers, lavatories, sinks, laun

dry sinks, floor drains, urinals, drinking fountains, dental units, and similar fixtures shall be of standard design, weight and shall be of ABS, cast-brass, cast-iron, lead, PP, PVC, or other approved material. An exposed and readily accessible drawn-copper alloy tubing trap, not less than 17 B & S Gauge (0.045 inch) (1.143 mm), shall be permitted to be used on fixtures discharging domestic sewage.

Exception s :

Frequently asked questions

How deep must a trap seal be?

Between 2 inches (51 mm) and 4 inches (102 mm), unless the AHJ requires a deeper seal. § 1005.1

When is a trap seal primer required?

A trap seal primer is required for floor drains or similar traps that are directly connected to the drainage system and subject to infrequent use, unless the AHJ determines it is unnecessary. § 1007.1

Does the primer have to be serviceable?

Yes — trap seal primers shall be accessible for maintenance. § 1007.1

Can I use a trap with movable parts or a bladder?

No — traps that depend on movable parts for the seal are prohibited (see trap requirements elsewhere in Chapter 10).

What if my trap evaporates between uses?

If evaporation is a concern because the trap is infrequently used, install an accessible trap primer per § 1007.1 to maintain the required trap seal depth. § 1007.1

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Related in the CPC

Trap seal primer devices: standards and compliance

Floor drain and building trap special requirements

Trap seals, floor drains and primers

California Plumbing Code

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