Building Code Glossary
Water Main: Building Code Definition
How the IPC 2009 define water main, where the wording differs, and which chapters depend on the term.
On this page
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.
Direct answer
Water main is a defined term in the International Plumbing Code (IPC) 2009, in Definitions. The code's own words are: “A water supply pipe or system of pipes, installed and maintained by a city, township, county, public utility company or other public entity, on public property, in the street or in an approved dedicated easement of public or community use.” No other I-Code in this corpus defines it, so the IPC 2009 definition is the one to work from. The term is used in 7 chapters of this corpus, most often in Fire Protection Systems (IFC 2009), Special Detailed Requirements Based on Use and Occupancy (IBC 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, Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.
What does this term mean?
Water Main — IPC 2009, Definitions:
A water supply pipe or system of pipes, installed and maintained by a city, township, county, public utility company or other public entity, on public property, in the street or in an approved dedicated easement of public or community use.
What must be verified before using this guidance?
Water Main is defined once in this corpus, in the Definitions chapter of the International Plumbing Code (IPC) 2009:
A water supply pipe or system of pipes, installed and maintained by a city, township, county, public utility company or other public entity, on public property, in the street or in an approved dedicated easement of public or community use.
Where water main is used in the code
The term appears in 7 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Fire Protection Systems | IFC 2009 | 6 |
| Special Detailed Requirements Based on Use and Occupancy | IBC 2009 | 4 |
| Definitions | IPC 2009 | 4 |
| Water Supply and Distribution | IPC 2009 | 4 |
| Definitions | IRC 2009 | 3 |
| Water Supply and Distribution | IRC 2009 | 3 |
| Fire Service Features | IFC 2009 | 2 |
The term in use
How the code actually writes about water main, quoted from the 2009 text hosted here:
Separate supply piping shall be provided between each connection to the water main and the pumps.
Where street water main pressures fluctuate, the building water distribution system shall be designed for the minimum pressure available.
The terms water main is built out of
The definition above leans on 2 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what water main covers:
- Approved — IBC 2009: Acceptable to the code official or authority having jurisdiction.
- System — IFC 2009: An assembly of equipment consisting of a tank, container or containers, appurtenances, pumps, compressors and connecting piping.
Water Main: 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 IPC | Definitions | |
| Re-check the requirement that uses it | Fire Protection Systems (IFC 2009) | |
| Re-check the requirement that uses it | Special Detailed Requirements Based on Use and Occupancy (IBC 2009) | |
| Re-check the requirement that uses it | Definitions (IPC 2009) | |
| Re-check the requirement that uses it | Water Supply and Distribution (IPC 2009) | |
| Confirm the dependent definition | Approved | |
| 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?
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 water main?
The International Plumbing Code (IPC) 2009 defines it in Definitions as: “A water supply pipe or system of pipes, installed and maintained by a city, township, county, public utility company or other public entity, on public property, in the street or in an approved dedicated easement of public or community use.” 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 water main?
In this corpus the term is used across 7 chapters, led by Fire Protection 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 IPC mean in plumbing?
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 water main, which the IPC 2009 defines as “A water supply pipe or system of pipes, installed and maintained by a city, township, county, public utility company or other public entity, on public property, in the street or in an approved dedicated easement of public or community use.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.
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