Updated 2026-09-07

Building Code Glossary

Drain: Building Code Definition

How the IRC 2009, IPC 2009 define drain, where the wording differs, and which chapters depend on the term.

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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.

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Direct answer

Drain is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “Any pipe that carries soil and water-borne wastes in a building drainage system.” The IPC 2009 words it differently, in Definitions: “Any pipe that carries wastewater or water-borne wastes in a building drainage system.” 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 73 chapters of this corpus, most often in Sanitary Drainage (IPC 2009), Vents (IPC 2009), Flammable and Combustible Liquids (IFC 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?

Drain — IRC 2009, Definitions:

Any pipe that carries soil and water-borne wastes in a building drainage system.

Labeled code-term definition diagram: Drain: Building Code Definition — How the IRC 2009, IPC 2009 define drain, where the wording differs, and which chapters depend on the term.

What must be verified before using this guidance?

Two of the I-Codes in this corpus define Drain, and the wording is not identical — read the version that governs your question.

Code	Where it is defined	Definition
IRC 2009	Definitions	Any pipe that carries soil and water-borne wastes in a building drainage system.
IPC 2009	Definitions	Any pipe that carries wastewater or water-borne wastes in a building drainage system.

Where drain is used in the code

The term appears in 73 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

Chapter	Code	Mentions
Sanitary Drainage	IPC 2009	181
Vents	IPC 2009	161
Flammable and Combustible Liquids	IFC 2009	153
Sanitary Drainage	IRC 2009	142
Definitions	IPC 2009	120
General Regulations	IPC 2009	102
Storm Drainage	IPC 2009	99
Vents	IRC 2009	97
Heating and Cooling Equipment	IRC 2009	86
General Regulations	IMC 2009	72
Definitions	IRC 2009	71
Foundations	IRC 2009	64

61 further chapters mention the term.

The term in use

How the code actually writes about drain, quoted from the 2009 text hosted here:

Where a buildingsewer or building drain is installed on filled or unstable ground, the drainage pipe shall conform to one of the standards for ABS plastic pipe, cast-iron pipe, copper or copper-alloy tubing, or PVC plastic pipe listed in Table 702.3.

— IPC 2009 §703.2

The vent system serving each building drain shall have at least one vent pipe that extends to the outdoors.

— IPC 2009 §903.1

Vent pipes shall be installed such that they will drain toward the tank without sags or traps in which liquid can collect.

— IFC 2009 §3404.2.7.3.4

The terms drain is built out of

The definition above leans on 3 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what drain covers:

Drainage System — IPC 2009: Piping within a public or private premise that conveys sewage, rainwater or other liquid wastes to a point of disposal.
Building — IBC 2009: Any structure used or intended for supporting or sheltering any use or occupancy.
System — IFC 2009: An assembly of equipment consisting of a tank, container or containers, appurtenances, pumps, compressors and connecting piping.

Drain: 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	Sanitary Drainage (IPC 2009)
Re-check the requirement that uses it	Vents (IPC 2009)
Re-check the requirement that uses it	Flammable and Combustible Liquids (IFC 2009)
Re-check the requirement that uses it	Sanitary Drainage (IRC 2009)
Confirm the dependent definition	Drainage System
Confirm the dependent definition	Building
Confirm the dependent definition	System
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.

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 drain?

The International Residential Code (IRC) 2009 defines it in Definitions as: “Any pipe that carries soil and water-borne wastes in a building drainage system.” 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 drain?

In this corpus the term is used across 73 chapters, led by Sanitary Drainage 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 building drain?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “Any pipe that carries soil and water-borne wastes in a building drainage system.” It is defined in IRC 2009, IPC 2009. It is not the same as Building, which the IBC 2009 defines separately as “Any structure used or intended for supporting or sheltering any use or occupancy.” 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.

What is a 1% slope for drainage?

Slope is a separate defined term. The IRC 2009 defines it as: “The fall (pitch) of a line of pipe in reference to a horizontal plane. In drainage, the slope is expressed as the fall in units vertical per units horizontal (percent) for a length of pipe.” That is not the same as drain, which the IRC 2009 defines as “Any pipe that carries soil and water-borne wastes in a building drainage system.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

Is an IR drain the same as a JP drain?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “Any pipe that carries soil and water-borne wastes in a building drainage system.” 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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