Building Code Glossary
Water-hammer Arrestor: Building Code Definition
How the IPC 2009 define water-hammer arrestor, 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-hammer arrestor is a defined term in the International Plumbing Code (IPC) 2009, in Definitions. The code's own words are: “A device utilized to absorb the pressure surge (water hammer) that occurs when water flow is suddenly stopped in a water supply system.” 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 4 chapters of this corpus, most often in Water Supply and Distribution (IPC 2009), Hydronic Piping (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, Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.
What does this term mean?
Water-hammer Arrestor — IPC 2009, Definitions:
A device utilized to absorb the pressure surge (water hammer) that occurs when water flow is suddenly stopped in a water supply system.
What must be verified before using this guidance?
Water-hammer Arrestor is defined once in this corpus, in the Definitions chapter of the International Plumbing Code (IPC) 2009:
A device utilized to absorb the pressure surge (water hammer) that occurs when water flow is suddenly stopped in a water supply system.
Where water-hammer arrestor 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 |
|---|---|---|
| Water Supply and Distribution | IPC 2009 | 3 |
| Hydronic Piping | IMC 2009 | 1 |
| Definitions | IPC 2009 | 1 |
| Water Supply and Distribution | IRC 2009 | 1 |
The term in use
How the code actually writes about water-hammer arrestor, quoted from the 2009 text hosted here:
A water-hammer arrestor shall be installed where quick-closing valves are utilized.
Where a quick-closing valve creates water hammer, an approved water-hammer arrestor shall be installed.
The terms water-hammer arrestor is built out of
The definition above leans on 3 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what water-hammer arrestor covers:
- Water Supply System — IPC 2009: The water service pipe, water distribution pipes, and the necessary connecting pipes, fittings, control valves and all appurtenances in or adjacent to the structure or premises.
- System — IFC 2009: An assembly of equipment consisting of a tank, container or containers, appurtenances, pumps, compressors and connecting piping.
- Device — IRC 2009: Aunit of an electrical system that carries or controls electrical energy as it principal function.
Water-hammer Arrestor: 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 | Water Supply and Distribution (IPC 2009) | |
| Re-check the requirement that uses it | Hydronic Piping (IMC 2009) | |
| Re-check the requirement that uses it | Definitions (IPC 2009) | |
| Re-check the requirement that uses it | Water Supply and Distribution (IRC 2009) | |
| Confirm the dependent definition | Water Supply System | |
| Confirm the dependent definition | System | |
| Confirm the dependent definition | Device | |
| 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
- Water Supply System: Building Code Definition
- System: Building Code Definition
- Device: Building Code Definition
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-hammer arrestor?
The International Plumbing Code (IPC) 2009 defines it in Definitions as: “A device utilized to absorb the pressure surge (water hammer) that occurs when water flow is suddenly stopped in a water supply 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.
Which parts of the code depend on water-hammer arrestor?
In this corpus the term is used across 4 chapters, led by Water Supply and Distribution 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.
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