International Residential Code 2015 (IRC 2015)

Part I ‒ Administrative

Chapter 1 Scope and Administration

Part II ‒ Definitions

Chapter 2 Definitions

Part III ‒ Building Planning and Construction

Chapter 3 Building Planning

Chapter 4 Foundations

Chapter 5 Floors

Chapter 6 Wall Construction

Chapter 7 Wall Covering

Chapter 8 Roof-Ceiling Construction

Chapter 9 Roof Assemblies

Chapter 10 Chimneys and Fireplaces

Part IV ‒ Energy Conservation

Chapter 11 [RE] Energy Efficiency


Part V ‒ Mechanical

Chapter 12 Mechanical Administration

Chapter 13 General Mechanical System Requirements

Chapter 14 Heating and Cooling Equipment and Appliances

Chapter 15 Exhaust Systems

Chapter 16 Duct Systems

Chapter 17 Combustion Air

Chapter 18 Chimneys and Vents

Chapter 19 Special Appliances, Equipment and Systems

Chapter 20 Boilers and Water Heaters

Chapter 21 Hydronic Piping

Chapter 22 Special Piping and Storage Systems

Chapter 23 Solar Thermal Energy Systems

Part VI ‒ Fuel Gas

Chapter 24 Fuel Gas

Part VII ‒ Plumbing

Chapter 25 Plumbing Administration

Chapter 26 General Plumbing Requirements

Chapter 27 Plumbing Fixtures

Chapter 28 Water Heaters

Chapter 29 Water Supply and Distribution

Chapter 30 Sanitary Drainage

Chapter 31 Vents

Chapter 32 Traps

Chapter 33 Storm Drainage

Part VIII ‒ Electrical

Chapter 34 General Requirements

Chapter 35 Electrical Definitions

Chapter 36 Services

Chapter 37 Branch Circuit and Feeder Requirements

Chapter 38 Wiring Methods

Chapter 39 Power and Lighting Distribution

Chapter 40 Devices and Luminaires

Chapter 41 Appliance Installation

Chapter 42 Swimming Pools

Chapter 43 Class 2 Remote-Control, Signaling and Power-Limited Circuits

Part IX ‒ Referenced Standards

Chapter 44 Referenced Standards

Appendix A Sizing and Capacities of Gas Piping

Appendix B Sizing of Venting Systems Serving Appliances Equipped With Draft Hoods, Category I Appliances, and Appliances Listed for Use With Type B Vents

Appendix C Exit Terminals of Mechanical Draft and Direct-Vent Venting Systems

Appendix D Recommended Procedure for Safety Inspection of an Existing Appliance Installation

Appendix E Manufactured Housing Used as Dwellings

Appendix F Radon Control Methods

Appendix G Piping Standards for Various Applications

Appendix H Patio Covers

Appendix I Private Sewage Disposal

Appendix J Existing Buildings and Structures

Appendix K Sound Transmission

Appendix L Permit Fees


Appendix N Venting Methods

Appendix O Automatic Vehicular Gates

Appendix P Sizing of Water Piping System

Appendix Q Reserved

Appendix R Light Straw-Clay Construction

Appendix S Strawbale Construction

Appendix T Recommended Procedure for Worst-Case Testing of Atmospheric Venting Systems Under N1102.4 or N1105 Conditions ≤ 5ACH50


Chapter 32 Traps

This section has been amended at the state or city level. Amendments are shown in green text.

User note: Code change proposals to this chapter will be considered by the IRC – Plumbing and Mechanical Code Development Committee during the 2015 (Group A) Code Development Cycle. See explanation on page iv.
Traps shall be of standard design, shall have smooth uniform internal waterways, shall be self-cleaning and shall not have interior partitions except where integral with the fixture. Traps shall be constructed of lead, cast iron, copper or copper alloy or approved plastic. Copper or copper alloy traps shall be not less than No. 20 gage (0.8 mm) thickness. Solid connections, slip joints and couplings shall be permitted to be used on the trap inlet, trap outlet, or within the trap seal. Slip joints shall be accessible.
Each fixture trap shall have a liquid seal of not less than 2 inches (51 mm) and not more than 4 inches (102 mm).
Traps seals of emergency floor drain traps and traps subject to evaporation shall be protected by one of the methods in Sections P3201.2.1.1 through P3201.2.1.4.
A potable water-supplied trap seal primer valve shall supply water to the trap. Water-supplied trap seal primer valves shall conform to ASSE 1018. The discharge pipe from the trap seal primer valve shall connect to the trap above the trap seal on the inlet side of the trap.
A reclaimed or gray-water-supplied trap seal primer valve shall supply water to the trap. Water-supplied trap seal primer valves shall conform to ASSE 1018. The quality of reclaimed or gray water supplied to trap seal primer valves shall be in accordance with the requirements of the manufacturer of the trap seal primer valve. The discharge pipe from the trap seal primer valve shall connect to the trap above the trap seal on the inlet side of the trap.
A waste-water-supplied trap primer device shall supply water to the trap. Waste-water-supplied trap primer devices shall conform to ASSE 1044. The discharge pipe from the trap seal primer device shall connect to the trap above the trap seal on the inlet side of the trap.
A barrier-type trap seal protection device shall protect the floor drain trap seal from evaporation. Barrier-type floor drain trap seal protection devices shall conform to ASSE 1072. The devices shall be installed in accordance with the manufacturer's instructions.
Traps shall be set level with respect to their water seals and shall be protected from freezing. Trap seals shall be protected from siphonage, aspiration or back pressure by an approved system of venting (see Section P3101).
Building traps shall be prohibited.
The following types of traps are prohibited:

1. Bell traps.

2. Separate fixture traps with interior partitions, except those lavatory traps made of plastic, stainless steel or other corrosion-resistant material.

3. "S" traps.

4. Drum traps.

5. Trap designs with moving parts.
Each plumbing fixture shall be separately trapped by a water seal trap. The vertical distance from the fixture outlet to the trap weir shall not exceed 24 inches (610 mm) and the horizontal distance shall not exceed 30 inches (762 mm) measured from the center line of the fixture outlet to the centerline of the inlet of the trap. The height of a clothes washer standpipe above a trap shall conform to Section P2706.1.2. Fixtures shall not be double trapped.


1. Fixtures that have integral traps.

2. A single trap shall be permitted to serve two or three like fixtures limited to kitchen sinks, laundry tubs and lavatories. Such fixtures shall be adjacent to each other and located in the same room with a continuous waste arrangement. The trap shall be installed at the center fixture where three fixtures are installed. Common trapped fixture outlets shall be not more than 30 inches (762 mm) apart.

3. Connection of a laundry tray waste line into a standpipe for the automatic clothes-washer drain shall be permitted in accordance with Section P2706.1.2.1.
Trap sizes for plumbing fixtures shall be as indicated in Table P3201.7. Where the tailpiece of a plumbing fixture is larger than that indicated in Table P3201.7, the trap size shall be the same nominal size as the fixture tailpiece. A trap shall not be larger than the drainage pipe into which the trap discharges.


Bathtub (with or without shower head and/or
whirlpool attachments)
Bidet 11/4
Clothes washer standpipe 2
Dishwasher (on separate trap) 11/2
Floor drain 2
Kitchen sink (one or two traps, with or
without dishwasher and food waste disposer)

Laundry tub (one or more compartments) 11/2
Lavatory 11/4
Shower (based on the total flow rate through
showerheads and bodysprays)
Flow rate:
5.7 gpm and less 11/2
More than 5.7 gpm up to 12.3 gpm 2
More than 12.3 gpm up to 25.8 gpm 3
More than 25.8 gpm up to 55.6 gpm 4

For SI: 1 inch = 25.4 mm.
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