Building Code Glossary
Drainage System: Building Code Definition
How the IPC 2009 define drainage system, 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
Drainage system is a defined term in the International Plumbing Code (IPC) 2009, in Definitions. The code's own words are: “Piping within a public or private premise that conveys sewage, rainwater or other liquid wastes to a point of disposal. A drainage system does not include the mains of a public sewer system or a private or public sewage treatment or disposal plant.” 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 38 chapters of this corpus, most often in Definitions (IPC 2009), Sanitary Drainage (IPC 2009), Indirect/special Waste (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?
Drainage System — IPC 2009, Definitions:
Piping within a public or private premise that conveys sewage, rainwater or other liquid wastes to a point of disposal. A drainage system does not include the mains of a public sewer system or a private or public sewage treatment or disposal plant.
What must be verified before using this guidance?
Drainage System is defined once in this corpus, in the Definitions chapter of the International Plumbing Code (IPC) 2009:
Piping within a public or private premise that conveys sewage, rainwater or other liquid wastes to a point of disposal. A drainage system does not include the mains of a public sewer system or a private or public sewage treatment or disposal plant.
Where drainage system is used in the code
The term appears in 38 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 | IPC 2009 | 38 |
| Sanitary Drainage | IPC 2009 | 36 |
| Indirect/special Waste | IPC 2009 | 22 |
| Definitions | IRC 2009 | 17 |
| Sanitary Drainage | IRC 2009 | 17 |
| Hazardous Materials-general Provisions | IFC 2009 | 15 |
| Storm Drainage | IPC 2009 | 12 |
| Soils and Foundations | IBC 2009 | 11 |
| Structural Design | IBC 2009 | 10 |
| Foundations | IRC 2009 | 10 |
| General Regulations | IPC 2009 | 8 |
| Fixtures, Faucets and Fixture Fittings | IPC 2009 | 7 |
26 further chapters mention the term.
The term in use
How the code actually writes about drainage system, quoted from the 2009 text hosted here:
The sanitary drainage system shall be tested in accordance with Section 312.
All devices, appurtenances, appliances and apparatus intended to serve some special function, such as sterilization, distillation, processing, cooling, or storage of ice or foods, and that discharge to the drainage system, shall be provided with protection against backflow, flooding, fouling, contamination and stoppage of the drain.
Running threads and bands shall not be used in the drainage system.
The terms drainage system is built out of
The definition above leans on 5 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what drainage system covers:
- Public Sewer — IRC 2009: A common sewer directly controlled by public authority.
- Private — IPC 2009: In the classification of plumbing fixtures, "private" applies to fixtures in residences and apartments, and to fixtures in nonpublic toilet rooms of hotels and motels and similar installations in buildings where the plumbing fixtures are intended for utilization by a …
- Liquid — IBC 2009: A material that has a melting point that is equal to or less than 68°F (20°C) and a boiling point that is greater than 68°F (20°C) at 14.7 pounds per square inch absolute (psia) (101 kPa).
- Piping — IRC 2009: Where used in this code, “piping” refers to either pipe or tubing, or both.
- System — IFC 2009: An assembly of equipment consisting of a tank, container or containers, appurtenances, pumps, compressors and connecting piping.
Drainage System: 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 | Definitions (IPC 2009) | |
| Re-check the requirement that uses it | Sanitary Drainage (IPC 2009) | |
| Re-check the requirement that uses it | Indirect/special Waste (IPC 2009) | |
| Re-check the requirement that uses it | Definitions (IRC 2009) | |
| Confirm the dependent definition | Public Sewer | |
| Confirm the dependent definition | Private | |
| Confirm the dependent definition | Liquid | |
| 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
- Public Sewer: Building Code Definition
- Private: Building Code Definition
- System: Building Code Definition
- Sewage: 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 drainage system?
The International Plumbing Code (IPC) 2009 defines it in Definitions as: “Piping within a public or private premise that conveys sewage, rainwater or other liquid wastes to a point of disposal. A drainage system does not include the mains of a public sewer system or a private or public sewage treatment or disposal plant.” 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 drainage system?
In this corpus the term is used across 38 chapters, led by Definitions 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 the definition of a drainage system?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IPC 2009 states, in Definitions: “Piping within a public or private premise that conveys sewage, rainwater or other liquid wastes to a point of disposal. A drainage system does not include the mains of a public sewer system or a private or public sewage treatment or disposal plant.” 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.
Related pages
- Drain: Building Code Definition
Drain — IRC 2009 definition: Any pipe that carries soil and water-borne wastes in a building drainage system.
- Drainage Fitting: Building Code Definition
Drainage Fitting — IRC 2009 definition: A pipe fitting designed to provide connections in the drainage system that have provisions for establishing …
- Drainage Fittings: Building Code Definition
Drainage Fittings — IPC 2009 definition: Type of fitting or fittings utilized in the drainage system.
- Drip: Building Code Definition
Drip — IRC 2009 definition: The container placed at a low point in a system of piping to collect condensate and …
- Dry-chemical Extinguishing Agent: Building Code Definition
Dry-chemical Extinguishing Agent — IBC 2009 definition: A powder composed of small particles, usually of sodium bicarbonate, potassium bicarbonate, urea-potassium-based bic…
- Dry Cleaning Plant: Building Code Definition
Dry Cleaning Plant — IFC 2009 definition: A facility in which dry cleaning and associated operations are conducted, including the office, receiving area …