# Backwater Valve: Building Code Definition

> How the IRC 2009, IPC 2009 define backwater valve, where the wording differs, and which chapters depend on the term.

- Canonical: https://harth.build/resources/glossary/backwater-valve/
- Last updated: 2026-09-07
- Data source: 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.

## Key facts

| Fact | Value |
| --- | --- |
| Defined in | IRC 2009, IPC 2009 (2009 editions transcribed in this corpus) |
| Primary source | IRC 2009 Definitions (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 7 (counted across the codes hosted here) |
| Wording identical across codes | No (compare before citing one code's wording under another) |

## Direct answer

Backwater valve is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “A device installed in a drain or pipe to prevent backflow of sewage.” The IPC 2009 words it differently, in Definitions: “A device or valve installed in the bUilding drain or sewer pipe where a sewer is subject to backflow, and which prevents drainage or waste from backing up into a lower level or fixtures and causing a flooding condition.” The IPC 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 7 chapters of this corpus, most often in Sanitary Drainage (IPC 2009), Sanitary Drainage (IRC 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](https://nz.linkedin.com/in/barrington), Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.*

## What does this term mean?

**Backwater Valve** — IRC 2009, Definitions:

> A device installed in a drain or pipe to prevent backflow of sewage.

![Labeled code-term definition diagram: Backwater Valve: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/backwater-valve/diagram-1344.webp)

*How the IRC 2009, IPC 2009 define backwater valve, where the wording differs, and which chapters depend on the term.*

## What must be verified before using this guidance?

Two of the I-Codes in this corpus define **Backwater Valve**, and the wording is not identical — read the version that governs your question.

| Code | Where it is defined | Definition |
| --- | --- | --- |
| IRC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | A device installed in a drain or pipe to prevent backflow of sewage. |
| IPC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/definitions.md) | A device or valve installed in the bUilding drain or sewer pipe where a sewer is subject to backflow, and which prevents drainage or waste from backing up into a lower level or fixtures and causing a flooding condition. |

## Where backwater valve is used in the code

The term appears in 7 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Sanitary Drainage](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/sanitary-drainage.md) | IPC 2009 | 11 |
| [Sanitary Drainage](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/sanitary-drainage.md) | IRC 2009 | 10 |
| [Indirect/special Waste](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/indirect-special-waste.md) | IPC 2009 | 3 |
| [Storm Drainage](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/storm-drainage.md) | IPC 2009 | 3 |
| [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/definitions.md) | IPC 2009 | 1 |
| [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | IRC 2009 | 1 |
| [Storm Drainage](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/storm-drainage.md) | IRC 2009 | 1 |

### The term in use

How the code actually writes about backwater valve, quoted from the 2009 text hosted here:

> Where the flood level rims of plumbing fixtures are below the elevation of the manhole cover of the next upstream manhole in the public sewer, such fixtures shall be protected by a backwater valve installed in the bUilding drain, branch of the bUilding drain or horizontal branch serving such fixtures.

— [IPC 2009 §715.1](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/sanitary-drainage.md)

> Where the building is subject to backwater, the subsoil drain shall be protected by an accessibly located backwater valve.

— [IPC 2009 §1111.1](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/storm-drainage.md)


## The terms backwater valve 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 backwater valve covers:

- **[Building Drain](https://harth.build/resources/glossary/building-drain.md)** — IRC 2009: The lowest piping that collects the discharge from all other drainage piping inside the house and extends 30 inches (762 mm) in developed length of pipe, beyond the exterior walls and conveys the drainage to the building sewer.
- **[Building](https://harth.build/resources/glossary/building.md)** — IBC 2009: Any structure used or intended for supporting or sheltering any use or occupancy.
- **[Backflow](https://harth.build/resources/glossary/backflow.md)** — 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.
- **[Backing](https://harth.build/resources/glossary/backing.md)** — IBC 2009: The wall or surface to which the veneer is secured.
- **[Device](https://harth.build/resources/glossary/device.md)** — IRC 2009: Aunit of an electrical system that carries or controls electrical energy as it principal function.

## Backwater Valve: what to open, and in what order

Every row is a document this term depends on. The [ICC code library](https://codes.iccsafe.org/codes) and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) cover the middle rows.

| Check | Where | Confirmed |
| --- | --- | --- |
| Read the definition in the adopted IRC | Definitions | |
| Read the definition in the adopted IPC | Definitions | |
| Re-check the requirement that uses it | Sanitary Drainage (IPC 2009) | |
| Re-check the requirement that uses it | Sanitary Drainage (IRC 2009) | |
| Re-check the requirement that uses it | Indirect/special Waste (IPC 2009) | |
| Re-check the requirement that uses it | Storm Drainage (IPC 2009) | |
| Confirm the dependent definition | Building Drain | |
| Confirm the dependent definition | Building | |
| Confirm the dependent definition | Backflow | |
| 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](https://harth.build/resources/glossary.md)
- [Building Drain: Building Code Definition](https://harth.build/resources/glossary/building-drain.md)
- [Building: Building Code Definition](https://harth.build/resources/glossary/building.md)
- [Backflow: Building Code Definition](https://harth.build/resources/glossary/backflow.md)
- [Backing: Building Code Definition](https://harth.build/resources/glossary/backing.md)

## 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](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.

### Source links

- [codes.iccsafe.org](https://codes.iccsafe.org/codes)

- [iccsafe.org](https://www.iccsafe.org/advocacy/code-adoption-maps/)

## Frequently asked questions

### What is the code definition of backwater valve?

The International Residential Code (IRC) 2009 defines it in Definitions as: “A device installed in a drain or pipe to prevent backflow of sewage.” 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 backwater valve?

In this corpus the term is used across 7 chapters, led by Sanitary Drainage 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 backwater valve?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “A device installed in a drain or pipe to prevent backflow of sewage.” It is defined in IRC 2009, 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.

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