# Existing Installations: Building Code Definition

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

- Canonical: https://harth.build/resources/glossary/existing-installations/
- 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 | 6 (counted across the codes hosted here) |
| Wording identical across codes | Yes (compare before citing one code's wording under another) |

## Direct answer

Existing installations is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “Any plumbing system regulated by this code that was legally installed prior to the effective date of this code, or for which a permit to install has been issued.” The IPC 2009 carries the same definition word for word, so the term means the same thing in each. The term is used in 6 chapters of this corpus, most often in Building Services and Systems (IFC 2009), Scope and Administration (IMC 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. Record the jurisdiction, the adopted edition, the application date and any local amendment that rewrites the definition before you use it on a live project, because a term redefined by amendment changes every requirement that depends on it.

*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?

**Existing Installations** — IRC 2009, Definitions:

> Any plumbing system regulated by this code that was legally installed prior to the effective date of this code, or for which a permit to install has been issued.

![Labeled code-term definition diagram: Existing Installations: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/existing-installations/diagram-1344.webp)

*How the IRC 2009, IPC 2009 define existing installations, 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 **Existing Installations**, in identical words.

| Code | Where it is defined | Definition |
| --- | --- | --- |
| IRC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | Any plumbing system regulated by this code that was legally installed prior to the effective date of this code, or for which a permit to install has been issued. |
| IPC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/definitions.md) | Any plumbing system regulated by this code that was legally installed prior to the effective date of this code, or for which a permit to install has been issued. |

## Where existing installations is used in the code

The term appears in 6 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Building Services and Systems](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/building-services-and-systems.md) | IFC 2009 | 1 |
| [Scope and Administration](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/scope-and-administration.md) | IMC 2009 | 1 |
| [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/definitions.md) | IPC 2009 | 1 |
| [Scope and Administration](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/scope-and-administration.md) | IPC 2009 | 1 |
| [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | IRC 2009 | 1 |
| [Mechanical Administration](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/mechanical-administration.md) | IRC 2009 | 1 |

### The term in use

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

> Existing installations shall be maintained in accordance with the original approval.

— [IFC 2009 §604.1](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/building-services-and-systems.md)


## Existing Installations compared with Appliance, Existing

These two are the closest pair in the 2009 I-Codes: about 85 per cent of their defining words are the same. The code states both and compares neither, so the difference is worth naming.

| | Wording unique to it |
| --- | --- |
| **Existing Installations** (IRC 2009) | plumbing, system |
| [Appliance, Existing](https://harth.build/resources/glossary/appliance-existing.md) (IMC 2009) | appliance |

Everything else in the two definitions is shared. If a project turns on which of the two applies, those words are the whole of the test — and a local amendment that edits one of them without editing the other moves the boundary between existing installations and appliance, existing.

## The terms existing installations 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 existing installations covers:

- **[Plumbing System](https://harth.build/resources/glossary/plumbing-system.md)** — IRC 2009: Includes the water supply and distribution pipes, plumbing fixtures, supports and appurtenances; soil, waste and vent pipes; sanitary drains and building sewers to an approved point of disposal.
- **[Plumbing](https://harth.build/resources/glossary/plumbing.md)** — IRC 2009: For the purpose of this code, plumbing refers to those installations, repairs, maintenance and alterations regulated by Chapters 25 through 33.
- **[Permit](https://harth.build/resources/glossary/permit.md)** — IBC 2009: An official document or certificate issued by the authority having jurisdiction which authorizes performance of a specified activity.
- **[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.

## Existing Installations: 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 | Building Services and Systems (IFC 2009) | |
| Re-check the requirement that uses it | Scope and Administration (IMC 2009) | |
| Re-check the requirement that uses it | Definitions (IPC 2009) | |
| Re-check the requirement that uses it | Scope and Administration (IPC 2009) | |
| Confirm the dependent definition | Plumbing System | |
| Confirm the dependent definition | Plumbing | |
| Confirm the dependent definition | Permit | |
| 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)
- [Plumbing System: Building Code Definition](https://harth.build/resources/glossary/plumbing-system.md)
- [Plumbing: Building Code Definition](https://harth.build/resources/glossary/plumbing.md)
- [System: Building Code Definition](https://harth.build/resources/glossary/system.md)
- [Permit: Building Code Definition](https://harth.build/resources/glossary/permit.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 existing installations?

The International Residential Code (IRC) 2009 defines it in Definitions as: “Any plumbing system regulated by this code that was legally installed prior to the effective date of this code, or for which a permit to install has been issued.” 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 existing installations?

In this corpus the term is used across 6 chapters, led by Building Services and Systems in the IFC 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 does IRC mean in building code?

Building is a separate defined term. The IBC 2009 defines it as: “Any structure used or intended for supporting or sheltering any use or occupancy.” That is not the same as existing installations, which the IRC 2009 defines as “Any plumbing system regulated by this code that was legally installed prior to the effective date of this code, or for which a permit to install has been issued.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

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