Building Code Glossary
Transition Fittings, Plastic to Steel: Building Code Definition
How the IRC 2009, IMC 2009 define transition fittings, plastic to steel, 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
Transition fittings, plastic to steel is a defined term in the International Residential Code (IRC) 2009, in Fuel Gas. The code's own words are: “An adapter for joining plastic pipe to steel pipe. The purpose of this fitting is to provide a permanent, pressure-tight connection between two materials that cannot be joined directly one to another.” The IMC 2009 defines the same term with different wording, so the controlling text depends on which code governs the question in front of you — the comparison below sets the versions side by side. The term is used in 2 chapters of this corpus, most often in Definitions (IMC 2009), Fuel Gas (IRC 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?
Transition Fittings, Plastic to Steel — IRC 2009, Fuel Gas:
An adapter for joining plastic pipe to steel pipe. The purpose of this fitting is to provide a permanent, pressure-tight connection between two materials that cannot be joined directly one to another.
What must be verified before using this guidance?
Two of the I-Codes in this corpus define Transition Fittings, Plastic to Steel, and the wording is not identical — read the version that governs your question.
| Code | Where it is defined | Definition |
|---|---|---|
| IRC 2009 | Fuel Gas | An adapter for joining plastic pipe to steel pipe. The purpose of this fitting is to provide a permanent, pressure-tight connection between two materials that cannot be joined directly one to another. |
| IMC 2009 | Definitions | An adapter for joining plastic pipe to steel pipe. The purpose of this fitting is to provide a permanent, pressure-tight connection between two materials which cannot be joined directly one to another. |
Where transition fittings, plastic to steel is used in the code
The term appears in 2 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Definitions | IMC 2009 | 1 |
| Fuel Gas | IRC 2009 | 1 |
The terms transition fittings, plastic to steel 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 transition fittings, plastic to steel covers:
- Fitting — IRC 2009: An accessory such as a locknut, bushing or other part of a wiring system that is intended primarily to perform a mechanical rather than an electrical function.
- Steel — IFC 2009: Hot-or cold-rolled as defined by the International Building Code.
Transition Fittings, Plastic to Steel: 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 | |
| Read the definition in the adopted IMC | Definitions | |
| Re-check the requirement that uses it | Definitions (IMC 2009) | |
| Re-check the requirement that uses it | Fuel Gas (IRC 2009) | |
| Confirm the dependent definition | Fitting | |
| Confirm the dependent definition | Steel | |
| 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 transition fittings, plastic to steel?
The International Residential Code (IRC) 2009 defines it in Fuel Gas as: “An adapter for joining plastic pipe to steel pipe. The purpose of this fitting is to provide a permanent, pressure-tight connection between two materials that cannot be joined directly one to another.” 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 transition fittings, plastic to steel?
In this corpus the term is used across 2 chapters, led by Definitions in the IMC 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 are transition fittings?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Fuel Gas: “An adapter for joining plastic pipe to steel pipe. The purpose of this fitting is to provide a permanent, pressure-tight connection between two materials that cannot be joined directly one to another.” It is defined in IRC 2009, IMC 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.
Related pages
- Toxic: Building Code Definition
Toxic — IBC 2009 definition: A chemical falling within any of the following categories:
- Transient Aircraft: Building Code Definition
Transient Aircraft — IBC 2009 definition: Aircraft based at another location and at the transient location for not more than 90 days.
- Transient: Building Code Definition
Transient — IBC 2009 definition: Occupancy of a dwelling unit or sleeping unit for not more than 30 days.
- Transverse Flue Space: Building Code Definition
Transverse Flue Space — IFC 2009 definition: The space between rows of storage parallel to the direction of loading.
- Trap Seal: Building Code Definition
Trap Seal — IRC 2009 definition: The trap seal is the maximum vertical depth of liquid that a trap will retain, measured …
- Trap: Building Code Definition
Trap — IRC 2009 definition: A fitting, either separate or built into a fixture, that provides a liquid seal to prevent …