Building Code Glossary
Trap: Building Code Definition
How the IRC 2009, IPC 2009 define trap, where the wording differs, and which chapters depend on the term.
On this page
Last updated September 7, 2026 · Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The [ICC code library](https://codes.iccsafe.org/codes) publishes the current model text and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) show which edition a jurisdiction has adopted; those sources control.
Direct answer
Trap is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “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 waste water through it.” The IPC 2009 defines the same term with different wording, so the controlling text depends on which code governs the question in front of you — the comparison below sets the versions side by side. The term is used in 65 chapters of this corpus, most often in Traps, Interceptors and Separators (IPC 2009), Traps (IRC 2009), Wall Construction (IRC 2009). These pages transcribe the 2009 model text; verify the definition against the edition and amendments your authority having jurisdiction has adopted.
Content and cited inputs reviewed by Scott Barrington, Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.
What does this term mean?
Trap — IRC 2009, Definitions:
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 waste water through it.
What must be verified before using this guidance?
Two of the I-Codes in this corpus define Trap, and the wording is not identical — read the version that governs your question.
| Code | Where it is defined | Definition |
|---|---|---|
| IRC 2009 | Definitions | 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 waste water through it. |
| IPC 2009 | Definitions | A fitting or device that provides a liquid seal to prevent the emission of sewer gases without materially affecting the flow of sewage or wastewater through the trap. |
Where trap is used in the code
The term appears in 65 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Traps, Interceptors and Separators | IPC 2009 | 77 |
| Traps | IRC 2009 | 57 |
| Wall Construction | IRC 2009 | 49 |
| Roof-ceiling Construction | IRC 2009 | 30 |
| Vents | IRC 2009 | 30 |
| Floors | IRC 2009 | 25 |
| Vents | IPC 2009 | 24 |
| Definitions | IPC 2009 | 22 |
| Definitions | IRC 2009 | 21 |
| Wood | IBC 2009 | 20 |
| Fixtures, Faucets and Fixture Fittings | IPC 2009 | 19 |
| Sanitary Drainage | IPC 2009 | 19 |
53 further chapters mention the term.
The term in use
How the code actually writes about trap, quoted from the 2009 text hosted here:
Each plumbing fixture shall be separately trapped by a liquid-seal trap, except as otherwise permitted by this code.
Solid connections, slipjoints and couplings are permitted to be used on the trap inlet, trap outlet, or within the trap seal.
The plumbing system shall be provided with a system of vent piping that will permit the admission or emission of air so that the seal of any fixture trap shall not be subjected to a pneumatic pressure differential of more than 1 inch of water column (249 Pa).
The terms trap is built out of
The definition above leans on 5 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what trap covers:
- Fitting — IRC 2009: An accessory such as a locknut, bushing or other part of a wiring system that is intended primarily to perform a mechanical rather than an electrical function.
- Liquid — IBC 2009: A material that has a melting point that is equal to or less than 68°F (20°C) and a boiling point that is greater than 68°F (20°C) at 14.7 pounds per square inch absolute (psia) (101 kPa).
- Device — IRC 2009: Aunit of an electrical system that carries or controls electrical energy as it principal function.
- Sewage — IRC 2009: Any liquid waste containing animal matter, vegetable matter or other impurity in suspension or solution.
- Waste — IRC 2009: Liquid-borne waste that is free of fecal matter.
Trap: what to open, and in what order
Every row is a document this term depends on. The ICC code library and the ICC adoption maps cover the middle rows.
| Check | Where | Confirmed |
|---|---|---|
| Read the definition in the adopted IRC | Definitions | |
| Read the definition in the adopted IPC | Definitions | |
| Re-check the requirement that uses it | Traps, Interceptors and Separators (IPC 2009) | |
| Re-check the requirement that uses it | Traps (IRC 2009) | |
| Re-check the requirement that uses it | Wall Construction (IRC 2009) | |
| Re-check the requirement that uses it | Roof-ceiling Construction (IRC 2009) | |
| Confirm the dependent definition | Fitting | |
| Confirm the dependent definition | Liquid | |
| Confirm the dependent definition | Device | |
| Local amendment to any of the above | Jurisdiction's amendment list |
A research aid, not a code determination. The authority having jurisdiction decides which edition and which amendments apply.
Where can you explore related guidance?
- Explore all glossary guidance
- Fitting: Building Code Definition
- Sewage: Building Code Definition
- Liquid: Building Code Definition
- Device: Building Code Definition
Sources and method
Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The ICC code library publishes the current model text and the ICC adoption maps show which edition a jurisdiction has adopted; those sources control.
Source links
Frequently asked questions
What is the code definition of trap?
The International Residential Code (IRC) 2009 defines it in Definitions as: “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 waste water through it.” The 2009 model text is reproduced here; the definition that binds your project is the one in the edition your jurisdiction has adopted, as amended locally.
Which parts of the code depend on trap?
In this corpus the term is used across 65 chapters, led by Traps, Interceptors and Separators in the IPC 2009. Those are the sections whose scope moves if the definition is amended locally, so read them together with Chapter 2 rather than on their own.
What is the definition of a trap?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “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 waste water through it.” It is defined in IRC 2009, IPC 2009. Because it is a defined term, whatever the adopted edition says it means is what every section using it means — so check Chapter 2 of that edition and any local amendment before relying on this wording.
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