# Drainage Fitting: Building Code Definition

> How the IRC 2009 define drainage fitting, where the wording differs, and which chapters depend on the term.

- Canonical: https://harth.build/resources/glossary/drainage-fitting/
- Last updated: 2026-09-07
- Data source: 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.

## Key facts

| Fact | Value |
| --- | --- |
| Defined in | IRC 2009 (2009 editions transcribed in this corpus) |
| Primary source | IRC 2009 Definitions (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 4 (counted across the codes hosted here) |
| Wording identical across codes | Single code (compare before citing one code's wording under another) |

## Direct answer

Drainage fitting is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “A pipe fitting designed to provide connections in the drainage system that have provisions for establishing the desired slope in the system. These fittings are made from a variety of both metals and plastics. The methods of coupling provide for required slope in the system (see "Durham fitting").” No other I-Code in this corpus defines it, so the IRC 2009 definition is the one to work from. The term is used in 4 chapters of this corpus, most often in Sanitary Drainage (IRC 2009), Definitions (IRC 2009), Definitions (IPC 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](https://nz.linkedin.com/in/barrington), Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.*

## What does this term mean?

**Drainage Fitting** — IRC 2009, Definitions:

> A pipe fitting designed to provide connections in the drainage system that have provisions for establishing the desired slope in the system. These fittings are made from a variety of both metals and plastics. The methods of coupling provide for required slope in the system (see "Durham fitting").

![Labeled code-term definition diagram: Drainage Fitting: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/drainage-fitting/diagram-1344.webp)

*How the IRC 2009 define drainage fitting, where the wording differs, and which chapters depend on the term.*

## What must be verified before using this guidance?

**Drainage Fitting** is defined once in this corpus, in the [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) chapter of the International Residential Code (IRC) 2009:

> A pipe fitting designed to provide connections in the drainage system that have provisions for establishing the desired slope in the system. These fittings are made from a variety of both metals and plastics. The methods of coupling provide for required slope in the system (see "Durham fitting").

## Where drainage fitting is used in the code

The term appears in 4 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](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/sanitary-drainage.md) | IRC 2009 | 8 |
| [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | IRC 2009 | 5 |
| [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/definitions.md) | IPC 2009 | 3 |
| [Sanitary Drainage](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/sanitary-drainage.md) | IPC 2009 | 3 |

## The terms drainage fitting is built out of

The definition above leans on 4 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what drainage fitting covers:

- **[Drainage System](https://harth.build/resources/glossary/drainage-system.md)** — IPC 2009: Piping within a public or private premise that conveys sewage, rainwater or other liquid wastes to a point of disposal.
- **[Fitting](https://harth.build/resources/glossary/fitting.md)** — 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.
- **[System](https://harth.build/resources/glossary/system.md)** — IFC 2009: An assembly of equipment consisting of a tank, container or containers, appurtenances, pumps, compressors and connecting piping.
- **[Slope](https://harth.build/resources/glossary/slope.md)** — IRC 2009: The fall (pitch) of a line of pipe in reference to a horizontal plane.

## Drainage Fitting: what to open, and in what order

Every row is a document this term depends on. The [ICC code library](https://codes.iccsafe.org/codes) and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) cover the middle rows.

| Check | Where | Confirmed |
| --- | --- | --- |
| Read the definition in the adopted IRC | Definitions | |
| Re-check the requirement that uses it | Sanitary Drainage (IRC 2009) | |
| Re-check the requirement that uses it | Definitions (IRC 2009) | |
| Re-check the requirement that uses it | Definitions (IPC 2009) | |
| Re-check the requirement that uses it | Sanitary Drainage (IPC 2009) | |
| Confirm the dependent definition | Drainage System | |
| Confirm the dependent definition | Fitting | |
| 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.

## Where can you explore related guidance?

- [Explore all glossary guidance](https://harth.build/resources/glossary.md)
- [Drainage System: Building Code Definition](https://harth.build/resources/glossary/drainage-system.md)
- [Fitting: Building Code Definition](https://harth.build/resources/glossary/fitting.md)
- [System: Building Code Definition](https://harth.build/resources/glossary/system.md)
- [Slope: Building Code Definition](https://harth.build/resources/glossary/slope.md)

## 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](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.

### Source links

- [codes.iccsafe.org](https://codes.iccsafe.org/codes)

- [iccsafe.org](https://www.iccsafe.org/advocacy/code-adoption-maps/)

## Frequently asked questions

### What is the code definition of drainage fitting?

The International Residential Code (IRC) 2009 defines it in Definitions as: “A pipe fitting designed to provide connections in the drainage system that have provisions for establishing the desired slope in the system. These fittings are made from a variety of both metals and plastics. The methods of coupling provide for required slope in the system (see "Durham fitting").” 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 drainage fitting?

In this corpus the term is used across 4 chapters, led by Sanitary Drainage in the IRC 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 are the 6 mandatory requirements for a drainage system?

Drainage System is a separate defined term. The IPC 2009 defines it as: “Piping within a public or private premise that conveys sewage, rainwater or other liquid wastes to a point of disposal. A drainage system does not include the mains of a public sewer system or a private or public sewage treatment or disposal plant.” That is not the same as drainage fitting, which the IRC 2009 defines as “A pipe fitting designed to provide connections in the drainage system that have provisions for establishing the desired slope in the system. These fittings are made from a variety of both metals and plastics. The methods of coupling provide for …” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

### What are the plumbing code fixture units for drainage pipes?

Plumbing is a separate defined term. The IRC 2009 defines it as: “For the purpose of this code, plumbing refers to those installations, repairs, maintenance and alterations regulated by Chapters 25 through 33.” That is not the same as drainage fitting, which the IRC 2009 defines as “A pipe fitting designed to provide connections in the drainage system that have provisions for establishing the desired slope in the system. These fittings are made from a variety of both metals and plastics. The methods of coupling provide for …” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

### 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 drainage fitting, which the IRC 2009 defines as “A pipe fitting designed to provide connections in the drainage system that have provisions for establishing the desired slope in the system. These fittings are made from a variety of both metals and plastics. The methods of coupling provide for …” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

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