Building Code Glossary
Relief Valve, Pressure: Building Code Definition
How the IRC 2009 define relief valve, pressure, 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
Relief valve, pressure is a defined term in the International Residential Code (IRC) 2009, in Fuel Gas. The code's own words are: “An automatic valve which opens and closes a relief vent, depending on whether the pressure is above or below a predetermined value.” No other I-Code in this corpus defines it, so the IRC 2009 definition is the one to work from. The term is used in 13 chapters of this corpus, most often in Cryogenic Fluids (IFC 2009), Motor Fuel-dispensing Facilities and Repair Garages (IFC 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?
Relief Valve, Pressure — IRC 2009, Fuel Gas:
An automatic valve which opens and closes a relief vent, depending on whether the pressure is above or below a predetermined value.
What must be verified before using this guidance?
Relief Valve, Pressure is defined once in this corpus, in the Fuel Gas chapter of the International Residential Code (IRC) 2009:
An automatic valve which opens and closes a relief vent, depending on whether the pressure is above or below a predetermined value.
Where relief valve, pressure is used in the code
The term appears in 13 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Cryogenic Fluids | IFC 2009 | 4 |
| Motor Fuel-dispensing Facilities and Repair Garages | IFC 2009 | 4 |
| Definitions | IPC 2009 | 4 |
| Water Heaters | IPC 2009 | 4 |
| Water Supply and Distribution | IPC 2009 | 4 |
| Flammable Gases and Flammable Cryogenic Fluids | IFC 2009 | 2 |
| Liquefied Petroleum Gases | IFC 2009 | 2 |
| Boilers, Water Heaters and Pressure Vessels | IMC 2009 | 2 |
| Refrigeration | IMC 2009 | 2 |
| Definitions | IMC 2009 | 1 |
| Hydronic Piping | IMC 2009 | 1 |
| Fuel Gas | IRC 2009 | 1 |
1 further chapters mention the term.
The term in use
How the code actually writes about relief valve, pressure, quoted from the 2009 text hosted here:
All storage water heaters operating above atmospheric pressure shall be provided with an approved, self-closing (levered) pressure relief valve and temperature relief valve or combination thereof.
Every pressure tank in a hydropneumatic pressure booster system shall be protected with a pressure relief valve.
Containers of liquefied flammable gases and flammable gases in solution shall be positioned in the upright position or positioned so that the pressure relief valve is in direct contact with the vapor space of the container.
Relief Valve, Pressure compared with Relief Valve, Vacuum
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 | |
|---|---|
| Relief Valve, Pressure (IRC 2009) | automatic, relief, pressure |
| Relief Valve, Vacuum (IRC 2009) | automatically, relieving, vacuum, within, hot, water, supply, system |
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 relief valve, pressure and relief valve, vacuum.
The terms relief valve, pressure 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 relief valve, pressure covers:
- Relief Vent — IPC 2009: A vent whose primary function is to provide circulation of air between drainage and vent systems.
- Automatic — IBC 2009: As applied to fire protection devices, a device or system providing an emergency function without the necessity for human intervention and activated as a result of a predetermined temperature rise, rate of temperature rise or combustion products.
- Valve — IRC 2009: A device used in piping to control the gas supply to any section of a system of piping or to an appliance.
Relief Valve, Pressure: 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 IRC | Fuel Gas | |
| Re-check the requirement that uses it | Cryogenic Fluids (IFC 2009) | |
| Re-check the requirement that uses it | Motor Fuel-dispensing Facilities and Repair Garages (IFC 2009) | |
| Re-check the requirement that uses it | Definitions (IPC 2009) | |
| Re-check the requirement that uses it | Water Heaters (IPC 2009) | |
| Confirm the dependent definition | Relief Vent | |
| Confirm the dependent definition | Automatic | |
| Confirm the dependent definition | Valve | |
| 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
- Relief Vent: Building Code Definition
- Automatic: Building Code Definition
- Valve: 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 relief valve, pressure?
The International Residential Code (IRC) 2009 defines it in Fuel Gas as: “An automatic valve which opens and closes a relief vent, depending on whether the pressure is above or below a predetermined value.” 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 relief valve, pressure?
In this corpus the term is used across 13 chapters, led by Cryogenic Fluids 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 is a pressure relief valve for 200 psi?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Fuel Gas: “An automatic valve which opens and closes a relief vent, depending on whether the pressure is above or below a predetermined value.” It is defined in IRC 2009. It is not the same as Pressure Relief Valve, which the IMC 2009 defines separately as “A pressure-actuated valve held closed by a spring or other means and designed to relieve pressure automatically in excess of the device's setting.” 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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