The International Plumbing Code (IPC), Explained
The International Plumbing Code (IPC) is the model plumbing code published by the International Code Council (ICC) and updated every three years, with the 2024 edition current. It sets minimum design and safety rules for water supply, drainage, and venting. It is not a national law. States and local jurisdictions adopt it, amend it, and enforce it, so the code that governs your job is whatever your area has adopted.
What is the International Plumbing Code?
The IPC is a model code, a template that governments can adopt into law. The ICC, based in Washington, D.C., writes and revises it through a consensus process on a three-year cycle. Recent editions are 2015, 2018, 2021, and 2024. It covers potable water distribution, water heaters, backflow prevention, pipe sizing, sanitary drainage, and venting.
By itself, the IPC is just a published book. It carries legal force only where a state, county, or city votes to adopt it. The code sets minimum safeguards, not best-case targets, so a jurisdiction can require more than the IPC but rarely less.
It applies to new construction, remodels, and repairs across residential and commercial buildings: single-family homes, apartments, schools, hospitals, and workplaces. The ICC also publishes companion books such as the International Residential Code, which contains its own plumbing provisions for one- and two-family homes.
IPC vs UPC: what is the difference?
The IPC and UPC are the two competing model plumbing codes in the US. The ICC publishes the IPC. The International Association of Plumbing and Mechanical Officials (IAPMO) publishes the Uniform Plumbing Code (UPC). Both run on three-year cycles and both carry 2024 editions. They diverge on venting, trap rules, approved materials, and sizing methods, so a detail that passes in one may fail in the other.
| Feature | IPC | UPC |
|---|---|---|
| Publisher | International Code Council (ICC) | IAPMO |
| Current edition | 2024 | 2024 |
| Update cycle | Every 3 years | Every 3 years |
| Where most used | Northeast, Southeast, much of the Midwest | West Coast and Mountain West |
| States adopting (approx.) | 34 to 37 plus D.C. | About 12 |
| Final code vote | Government code officials vote | ANSI consensus, broader voting body |
| Typical stance | More options for methods and materials | More prescriptive on some methods |
Neither code is universally stricter. They take different approaches to the same goal of safe, sanitary plumbing. Whichever one your area uses, the version that matters is the exact edition your jurisdiction adopted, along with any local changes to it.
Which states use the International Plumbing Code?
Most states use the IPC as their base plumbing code, concentrated in the Northeast, Southeast, and much of the Midwest, while roughly a dozen western states use the UPC. Several states run their own code or heavily amended versions. Adoption changes each code cycle and can vary within a state, so treat the table below as a general map, not a legal answer.
| Region (example states) | Common base code | Note |
|---|---|---|
| West Coast and Mountain West (California, Washington, Oregon, Nevada, Hawaii, Alaska, Idaho) | UPC-based | Often rebuilt into a state code, such as the California Plumbing Code |
| Northeast and Mid-Atlantic (New York, Pennsylvania, Maryland, Virginia, New Hampshire) | IPC-based | Usually adopted with state amendments |
| Southeast (Florida, Georgia, North Carolina, South Carolina, Tennessee) | IPC-based | Florida uses the IPC-derived Florida Building Code |
| Midwest (Ohio, Michigan, Indiana, Nebraska) | IPC-based, mostly | Some neighboring states differ |
| State-specific codes (Minnesota, New Jersey, Illinois, Massachusetts, Wisconsin) | Own or hybrid code | Not straight IPC or UPC |
| No statewide code (parts of Arizona, Kansas, Missouri, Wyoming) | Set locally | Each city or county picks its own code |
Sources disagree on the exact count and on a few borderline states, partly because assignments change with each cycle and partly because some states amend a model code so heavily it reads as its own. Use this table to know which family your state likely follows, then verify the specifics.
Why “adopted” does not mean unchanged
An “IPC state” rarely enforces the plain IPC. When a state or city adopts a model code, it usually attaches local amendments that change, delete, or add sections to fit regional conditions like freeze depth, seismic risk, or water scarcity. The enforceable rule is the adopted edition plus those amendments, read together.
This is why two homes in the same state can face different requirements. A city may adopt the 2021 IPC with its own changes while the county next door runs the 2018 edition. Editions also lag the model release: many areas are still on 2018 or 2021 in 2026, even though the 2024 books exist.
The office that settles all of this is the Authority Having Jurisdiction (AHJ), typically your city or county building or plumbing department. The AHJ decides which edition is in force, publishes the local amendments, issues permits, and inspects the work. The inspector’s reading of the code is final on your project.
How to find the plumbing code that applies to your job
Do not rely on “my state uses the IPC” for a real install. Trace it down to your specific address and edition. The steps below get you from the model code to the exact rules an inspector will hold you to, in the right order.
- Identify your AHJ, usually the city or county building or plumbing department for your address.
- Ask which model code and edition they enforce, for example the 2021 IPC or the 2024 UPC.
- Request the local amendments, since those override the base code where they conflict.
- Read the adopted edition. ICC Digital Codes and IAPMO both offer free read-only access online.
- Confirm permit and inspection requirements before any work starts.
- If a section is unclear, ask the AHJ or a licensed plumber. The inspector’s interpretation controls.
Codes change and interpretations vary, so verify current requirements with your AHJ every time rather than reusing an answer from an old job or another town.
How homeowners and pros actually use the code
Most people never read the full code. They hit it through specific requirements: whether a job needs a permit, what a water heater install must include, which fittings are legal, and how backflow gets protected. The IPC or UPC is the backbone behind each of those rules, and the specifics still route through your local AHJ and amendments.
Before a project, the common code-driven questions are narrow. Our companion guides cover the ones homeowners and pros ask most:
- Whether your project triggers a permit and inspection: see when a plumbing permit is required.
- What an inspector checks on a water heater, from the T&P valve to venting: see water heater code requirements.
- Which pipe, fittings, and fixtures meet the low-lead law: see lead-free plumbing rules.
- How cross-connections must be protected from contamination: see backflow prevention rules.
Treat the model code as the starting point and the AHJ as the final word. Confirm the adopted edition, read the local amendments, pull the permit, and let the inspection close the loop. That sequence keeps a job legal whether your state follows the IPC, the UPC, or a code of its own.
Frequently asked questions
Does the US have a national plumbing code?
No. The United States has no single national plumbing code. Two model codes compete: the International Plumbing Code (IPC) from the ICC and the Uniform Plumbing Code (UPC) from IAPMO. States and local jurisdictions adopt one, often amend it, and enforce it themselves. The code that binds your project is the local adopted edition, not a federal rule.
What is the difference between the IPC and the UPC?
The ICC publishes the IPC and IAPMO publishes the UPC. Both run on three-year cycles and both have 2024 editions. They differ on venting methods, trap and cleanout rules, approved materials, and pipe-sizing calculations. The IPC is more common in the East and Midwest, the UPC across the West. An install that passes one may not satisfy the other.
Which states use the International Plumbing Code?
Roughly 34 to 37 states plus Washington, D.C. use the IPC as their base plumbing code, concentrated in the Northeast, Southeast, and much of the Midwest. About 12 western states use the UPC instead. Adoption shifts each code cycle and several states run their own code, so confirm the current status with your local building department.
What is the latest edition of the International Plumbing Code?
The 2024 IPC is the current edition, released by the ICC in 2023. Prior editions include 2021, 2018, and 2015. Your jurisdiction may still enforce an older edition, because states and cities adopt new versions on their own timelines. Ask your AHJ which edition is in force before you rely on any specific section.
Is the International Plumbing Code free to read?
You can read the IPC free online through ICC Digital Codes in a read-only view, and the UPC through IAPMO in a similar format. Free access lets you look up sections, but printed and premium versions add search and annotation tools. Local amendments are separate documents, usually posted on your city or county building department website.
Who enforces the plumbing code?
Your local Authority Having Jurisdiction (AHJ) enforces the code, usually a city or county building or plumbing department. Inspectors review permitted work against the adopted edition plus local amendments, and their interpretation is final on your job. State agencies set the base code, but day-to-day enforcement, permits, and inspections happen at the local level.
Last reviewed: September 2026.