# Individual Sewage Disposal System: Building Code Definition

> How the IRC 2009, IPC 2009 define individual sewage disposal system, where the wording differs, and which chapters depend on the term.

- Canonical: https://harth.build/resources/glossary/individual-sewage-disposal-system/
- 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, IPC 2009 (2009 editions transcribed in this corpus) |
| Primary source | IRC 2009 Definitions (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 3 (counted across the codes hosted here) |
| Wording identical across codes | No (compare before citing one code's wording under another) |

## Direct answer

Individual sewage disposal system is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “A system for disposal of sewage by means of a septic tank or mechanical treatment, designed for use apart from a public sewer to serve a single establishment or building.” 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 3 chapters of this corpus, most often in Definitions (IPC 2009), Definitions (IRC 2009), General Plumbing Requirements (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](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?

**Individual Sewage Disposal System** — IRC 2009, Definitions:

> A system for disposal of sewage by means of a septic tank or mechanical treatment, designed for use apart from a public sewer to serve a single establishment or building.

![Labeled code-term definition diagram: Individual Sewage Disposal System: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/individual-sewage-disposal-system/diagram-1344.webp)

*How the IRC 2009, IPC 2009 define individual sewage disposal system, 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 **Individual Sewage Disposal System**, and the wording is not identical — read the version that governs your question.

| Code | Where it is defined | Definition |
| --- | --- | --- |
| IRC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | A system for disposal of sewage by means of a septic tank or mechanical treatment, designed for use apart from a public sewer to serve a single establishment or building. |
| IPC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/definitions.md) | A system for disposal of domestic sewage by means of a septic tank, cesspool or mechanical treatment, designed for utilization apart from a public sewer to serve a single establishment or building. |

## Where individual sewage disposal system is used in the code

The term appears in 3 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/definitions.md) | IPC 2009 | 2 |
| [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | IRC 2009 | 1 |
| [General Plumbing Requirements](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/general-plumbing-requirements.md) | IRC 2009 | 1 |

## The terms individual sewage disposal system 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 individual sewage disposal system covers:

- **[Public Sewer](https://harth.build/resources/glossary/public-sewer.md)** — IRC 2009: A common sewer directly controlled by public authority.
- **[Septic Tank](https://harth.build/resources/glossary/septic-tank.md)** — IRC 2009: A water-tight receptor that receives the discharge of a building sanitary drainage system and is constructed so as to separate solids from the liquid, digest organic matter through a period of detention, and allow the liquids to discharge into the …
- **[Building](https://harth.build/resources/glossary/building.md)** — IBC 2009: Any structure used or intended for supporting or sheltering any use or occupancy.
- **[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.
- **[Sewage](https://harth.build/resources/glossary/sewage.md)** — IRC 2009: Any liquid waste containing animal matter, vegetable matter or other impurity in suspension or solution.

## Individual Sewage Disposal System: 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 | |
| Read the definition in the adopted IPC | Definitions | |
| Re-check the requirement that uses it | Definitions (IPC 2009) | |
| Re-check the requirement that uses it | Definitions (IRC 2009) | |
| Re-check the requirement that uses it | General Plumbing Requirements (IRC 2009) | |
| Confirm the dependent definition | Public Sewer | |
| Confirm the dependent definition | Septic Tank | |
| Confirm the dependent definition | Building | |
| 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)
- [Public Sewer: Building Code Definition](https://harth.build/resources/glossary/public-sewer.md)
- [Septic Tank: Building Code Definition](https://harth.build/resources/glossary/septic-tank.md)
- [Building: Building Code Definition](https://harth.build/resources/glossary/building.md)
- [System: Building Code Definition](https://harth.build/resources/glossary/system.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 individual sewage disposal system?

The International Residential Code (IRC) 2009 defines it in Definitions as: “A system for disposal of sewage by means of a septic tank or mechanical treatment, designed for use apart from a public sewer to serve a single establishment or building.” 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 individual sewage disposal system?

In this corpus the term is used across 3 chapters, led by Definitions 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 a private sewage system called?

Private is a separate defined term. The IPC 2009 defines it as: “In the classification of plumbing fixtures, "private" applies to fixtures in residences and apartments, and to fixtures in nonpublic toilet rooms of hotels and motels and similar installations in buildings where the plumbing fixtures are intended for utilization by a family or an individual.” That is not the same as individual sewage disposal system, which the IRC 2009 defines as “A system for disposal of sewage by means of a septic tank or mechanical treatment, designed for use apart from a public sewer to serve a single establishment or building.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

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