Building Code Glossary
Vacuum Breaker: Building Code Definition
How the IPC 2009 define vacuum breaker, 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
Vacuum breaker is a defined term in the International Plumbing Code (IPC) 2009, in Definitions. The code's own words are: “A type of backflow preventer installed on openings subject to normal atmospheric pressure that prevents backflow by admitting atmospheric pressure through ports to the discharge side of the device.” 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 8 chapters of this corpus, most often in Water Supply and Distribution (IPC 2009), Water Supply and Distribution (IRC 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?
Vacuum Breaker — IPC 2009, Definitions:
A type of backflow preventer installed on openings subject to normal atmospheric pressure that prevents backflow by admitting atmospheric pressure through ports to the discharge side of the device.
What must be verified before using this guidance?
Vacuum Breaker is defined once in this corpus, in the Definitions chapter of the International Plumbing Code (IPC) 2009:
A type of backflow preventer installed on openings subject to normal atmospheric pressure that prevents backflow by admitting atmospheric pressure through ports to the discharge side of the device.
Where vacuum breaker is used in the code
The term appears in 8 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 | 62 |
| Water Supply and Distribution | IRC 2009 | 32 |
| Definitions | IPC 2009 | 4 |
| Fixtures, Faucets and Fixture Fittings | IPC 2009 | 4 |
| General Regulations | IPC 2009 | 4 |
| Sanitary Drainage | IPC 2009 | 2 |
| Plumbing Administration | IRC 2009 | 2 |
| Definitions | IRC 2009 | 1 |
The term in use
How the code actually writes about vacuum breaker, quoted from the 2009 text hosted here:
The water supply for hospital fixtures shall be protected against backflow with a reduced pressure principle backflow preventer, an atmospheric or spill-proof vacuum breaker, or an airgap.
Potable water openings and outlets shall be protected by an air gap, reduced pressure principle backflow preventer with atmospheric vent, atmospheric-type vacuum breaker, pressure-type vacuum breaker or hose connection backflow preventer.
Deck-mounted bath/shower transfer valves containing an integral atmospheric vacuum breaker shall conform to the requirements of ASME Al12 .18.7.
Vacuum Breaker compared with Vacuum Breakers
These two are the closest pair in the 2009 I-Codes: about 52 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 | |
|---|---|
| Vacuum Breaker (IPC 2009) | type, backflow, preventer, installed, openings, subject, normal |
| Vacuum Breakers (IRC 2009) | back, siphonage, water |
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 vacuum breaker and vacuum breakers.
The terms vacuum breaker 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 vacuum breaker covers:
- Atmospheric Pressure — IRC 2009: The pressure of the weight of air and water vapor on the surface of the earth, approximately 14.7 pounds per square inch (psia) (101 kPa absolute) at sea level.
- Backflow — IPC 2009: Pressure created by any means in the water distribution system, which by being in excess ofthe pressure in the water supply mains causes a potential backflow condition.
- Device — IRC 2009: Aunit of an electrical system that carries or controls electrical energy as it principal function.
Vacuum Breaker: 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 | Water Supply and Distribution (IRC 2009) | |
| Re-check the requirement that uses it | Definitions (IPC 2009) | |
| Re-check the requirement that uses it | Fixtures, Faucets and Fixture Fittings (IPC 2009) | |
| Confirm the dependent definition | Atmospheric Pressure | |
| Confirm the dependent definition | Backflow | |
| 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
- Atmospheric Pressure: Building Code Definition
- Backflow: 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 vacuum breaker?
The International Plumbing Code (IPC) 2009 defines it in Definitions as: “A type of backflow preventer installed on openings subject to normal atmospheric pressure that prevents backflow by admitting atmospheric pressure through ports to the discharge side of the device.” 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 vacuum breaker?
In this corpus the term is used across 8 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.
What is a vacuum breaker?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IPC 2009 states, in Definitions: “A type of backflow preventer installed on openings subject to normal atmospheric pressure that prevents backflow by admitting atmospheric pressure through ports to the discharge side of the device.” It is defined in 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.
Is a vacuum breaker considered a backflow preventer?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IPC 2009 states, in Definitions: “A type of backflow preventer installed on openings subject to normal atmospheric pressure that prevents backflow by admitting atmospheric pressure through ports to the discharge side of the device.” It is defined in IPC 2009. It is not the same as Backflow, which the IPC 2009 defines separately as “Pressure created by any means in the water distribution system, which by being in excess ofthe pressure in the water supply mains causes a potential backflow condition.” 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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