# Water Heater: Building Code Definition

> How the IRC 2009, IMC 2009, IPC 2009 define water heater, where the wording differs, and which chapters depend on the term.

- Canonical: https://harth.build/resources/glossary/water-heater/
- 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, IMC 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 | 22 (counted across the codes hosted here) |
| Wording identical across codes | Yes (compare before citing one code's wording under another) |

## Direct answer

Water heater is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “Any heating appliance or equipment that heats potable water and supplies such water to the potable hot water distribution system.” The IMC 2009, IPC 2009 carry the same definition word for word, so the term means the same thing in each. The term is used in 22 chapters of this corpus, most often in Water Heaters (IPC 2009), Water Heaters (IRC 2009), Boilers and Water Heaters (IRC 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?

**Water Heater** — IRC 2009, Definitions:

> Any heating appliance or equipment that heats potable water and supplies such water to the potable hot water distribution system.

![Labeled code-term definition diagram: Water Heater: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/water-heater/diagram-1344.webp)

*How the IRC 2009, IMC 2009, IPC 2009 define water heater, where the wording differs, and which chapters depend on the term.*

## What must be verified before using this guidance?

Three of the I-Codes in this corpus define **Water Heater**, 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 heating appliance or equipment that heats potable water and supplies such water to the potable hot water distribution system. |
| IMC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | Any heating appliance or equipment that heats potable water and supplies such water to the potable hot water distribution system. |
| IPC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/definitions.md) | Any heating appliance or equipment that heats potable water and supplies such water to the potable hot water distribution system. |

## Where water heater is used in the code

The term appears in 22 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Water Heaters](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/water-heaters.md) | IPC 2009 | 55 |
| [Water Heaters](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/water-heaters.md) | IRC 2009 | 39 |
| [Boilers and Water Heaters](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/boilers-and-water-heaters.md) | IRC 2009 | 29 |
| [Boilers, Water Heaters and Pressure Vessels](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/boilers-water-heaters-and-pressure-vessels.md) | IMC 2009 | 22 |
| [Water Supply and Distribution](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/water-supply-and-distribution.md) | IRC 2009 | 13 |
| [Swimming Pools](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/swimming-pools.md) | IRC 2009 | 10 |
| [Building Planning](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/building-planning.md) | IRC 2009 | 8 |
| [Water Supply and Distribution](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/water-supply-and-distribution.md) | IPC 2009 | 7 |
| [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) | IRC 2009 | 7 |
| [Residential Energy Efficiency](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/residential-energy-efficiency.md) | IECC 2009 | 4 |
| [General Regulations](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/general-regulations.md) | IPC 2009 | 4 |
| [Scope and Administration](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/scope-and-administration.md) | IPC 2009 | 3 |

_10 further chapters mention the term._

### The term in use

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

> Drain valves for emptying shall be installed at the bottom of each tank-type water heater and hot waterstorage tank.

— [IPC 2009 §501.3](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/water-heaters.md)

> Each dwelling shall have an approved automatic water heater or other type of domestic water-heating system sufficient to supply hot water to plumbing fixtures and appliances intended for bathing, washing or culinary purposes.

— [IRC 2009 §P2801.1](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/water-heaters.md)

> A readily accessible full-open valve shall be installed in the cold-water supply pipe to each water heater at or near the water heater.

— [IRC 2009 §P2903.9.2](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/water-supply-and-distribution.md)


## The terms water heater 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 water heater covers:

- **[Potable Water](https://harth.build/resources/glossary/potable-water.md)** — IRC 2009: Water free from impurities present in amounts sufficient to cause disease or harmful physiological effects and conforming in bacteriological and chemical quality to the requirements of the public health authority havingjurisdiction.
- **[Equipment](https://harth.build/resources/glossary/equipment.md)** — IRC 2009: All piping, ducts, vents, control devices and other components of systems other than appliances that are permanently installed and integrated to provide control of environmental conditions for buildings.
- **[Appliance](https://harth.build/resources/glossary/appliance.md)** — IRC 2009: Utilization equipment, normally built in standardized sizes or types, that is installed or connected as a unit to perform one or more functions such as clothes washing, air conditioning, food mixing, deep frying, etc.
- **[Hot Water](https://harth.build/resources/glossary/hot-water.md)** — IRC 2009: Water at a temperature greater than or equal to 110° P (43°C).
- **[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.

## Water Heater: 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 IMC | Definitions | |
| Read the definition in the adopted IPC | Definitions | |
| Re-check the requirement that uses it | Water Heaters (IPC 2009) | |
| Re-check the requirement that uses it | Water Heaters (IRC 2009) | |
| Re-check the requirement that uses it | Boilers and Water Heaters (IRC 2009) | |
| Re-check the requirement that uses it | Boilers, Water Heaters and Pressure Vessels (IMC 2009) | |
| Confirm the dependent definition | Potable Water | |
| Confirm the dependent definition | Equipment | |
| Confirm the dependent definition | Appliance | |
| 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)
- [Potable Water: Building Code Definition](https://harth.build/resources/glossary/potable-water.md)
- [Hot Water: Building Code Definition](https://harth.build/resources/glossary/hot-water.md)
- [Equipment: Building Code Definition](https://harth.build/resources/glossary/equipment.md)
- [Appliance: Building Code Definition](https://harth.build/resources/glossary/appliance.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 water heater?

The International Residential Code (IRC) 2009 defines it in Definitions as: “Any heating appliance or equipment that heats potable water and supplies such water to the potable hot water distribution 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.

### Do the I-Codes define water heater the same way?

In the 2009 editions transcribed here, yes: IRC 2009, IMC 2009, IPC 2009 carry the same wording, so the term means the same thing in each. Later editions do diverge on some terms, so confirm against the adopted edition rather than assuming the alignment holds.

### Which parts of the code depend on water heater?

In this corpus the term is used across 22 chapters, led by Water Heaters 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 water heater considered?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “Any heating appliance or equipment that heats potable water and supplies such water to the potable hot water distribution system.” It is defined in IRC 2009, IMC 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.

### What are the requirements for water heaters according to the Florida 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 water heater, which the IRC 2009 defines as “Any heating appliance or equipment that heats potable water and supplies such water to the potable hot water distribution system.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

### What is the NEC code for a hot water heater?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “Any heating appliance or equipment that heats potable water and supplies such water to the potable hot water distribution system.” It is defined in IRC 2009, IMC 2009, IPC 2009. It is not the same as Hot Water, which the IRC 2009 defines separately as “Water at a temperature greater than or equal to 110° P (43°C).” 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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