There is no single national plumbing license exam.
Each state board — or the city or county office where licensing is local — decides which test you sit, who delivers it, which code book it covers and whether it is open book.
PSI delivers state plumbing and HVAC licensing exams in 20 states and Prov in 8; the rest go to Pearson VUE, Prometric, IAPMO, ICC, NITC and boards that write their own.
Here is how the map works.
Who administers the plumbing license exam?
There is no single national test.
The board that issues your licence — a state plumbing board, a contractor licensing board, or the city or county office where licensing is local — picks the exam, and delivery is often contracted to a private testing company.
Which company that is changes at the state line.
PSI is the most common vendor: it delivers state plumbing and/or HVAC licensing exams in 20 states, with plumbing exams in California, Colorado, Maryland, Massachusetts, Michigan, Mississippi, New Jersey and Washington among them.
Prov (ProV) is next, delivering HVAC and/or plumbing exams in 8 states — it runs plumbing exams in Indiana, New Hampshire, Utah and West Virginia, delivers Vermont's ICC-based plumbing exam, and took over Tennessee's contractor exams for new bookings from July 1, 2026.
The rest of the map is a patchwork.
Pearson VUE delivers the Texas State Board of Plumbing Examiners' written exams, and Prometric runs Hawaii's exams.
In Montana, the Board of Plumbers approves your application and then schedules the exam through IAPMO, with the exam fees paid directly to IAPMO.
ICC exams serve cities and counties that use them — Philadelphia and Pittsburgh among them — and Kansas designates ICC, IAPMO or Prometric exams as its standard plumbing competency exams.
NITC handles Nevada's NBOPE plumber cards.
Some boards skip vendors entirely: Minnesota's Department of Labor and Industry, New York City's Department of Buildings and Omaha's plumbing board write and run their own exams.
And NASCLA, whose accredited exam covers commercial general building (plus electrical) rather than the plumbing trade, is only now developing a plumbing examination — subject-matter-expert recruitment is underway — so there is no NASCLA plumbing exam in use yet.
Treat every list like this one as a snapshot.
Vendors change — Tennessee's contractor exams moved to Prov for new bookings from July 1, 2026 — and our cross-state research compiled vendor names board by board without confirming one for every state, so no complete national vendor list exists in our vault.
Your board's candidate handbook names the current vendor, the fees and the booking process.
Your board's page is the source of record
Which code your exam tests: UPC, IPC or a state code
Every plumbing licence exam is built on a code book, and boards do not agree on which one.
The research found three patterns.
Some boards test the Uniform Plumbing Code (UPC): Montana's journeyman exam runs on the 2021 UPC as amended, Alaska's on the 2018 UPC, and the NBOPE exam used around Nevada is based on the currently adopted UPC.
Others test the International Plumbing Code (IPC): Louisiana's master plumber exam covers the 2021 IPC and the 2021 International Residential Code, and Washington, D.C.'s plumbing and gas exams reference the 2012 IPC and the 2012 International Fuel Gas Code.
A third group tests its own state code.
Massachusetts sits its plumbing exam on 248 CMR 10.00, the state's Uniform State Plumbing Code, and North Dakota requires the 2018 North Dakota Plumbing Code.
The same principle shows up next door, stated outright: Oklahoma's mechanical licensing exams test the statewide codes adopted by the Oklahoma Uniform Building Code Commission.
The logic is the same everywhere — the exam tests the plumbing code your state or city has actually adopted — and the edition matters as much as the title, since Montana tests a 2021 UPC where Alaska uses 2018.
IAPMO, which develops the Uniform Codes, publishes state-specific editions for California, Idaho, Minnesota, South Dakota and Washington, plus city codes such as Seattle's and Houston's.
What the research did not find is a complete national UPC-versus-IPC adoption map — no primary source maintains one — so this page names examples rather than a 50-state table.
Your board's exam notice names the code and the exact edition to study, and a full comparison of the two codes belongs to its own guide.
Open-book rules: what you can bring into the exam
Plumbing licence exams lean open book, but the status is the board's call and one exam can mix both modes.
Mississippi's contractor board runs all of its exams, its plumbing trade exams included, open book through PSI; Oregon's journeyman plumber exam is a 4-hour, 64-question open-book exam; and Montana's master plumber exam is open book, with candidates bringing their own tabbed code book.
But Nevada's NBOPE exam pairs 50 open-book questions with 100 closed-book sizing questions, and North Dakota's journeyman exam has five parts — two closed book, three open book.
When the exam is open book, the board also writes the book rules.
North Carolina's board requires candidates to bring their own approved references — hard-bound, spiral or ring-bound originals, with highlighting and permanently attached commercial tabs only.
Idaho allows the Contractors' Business and Law Reference Manual into the exam in a binder, pre-highlighted in advance but with no writing during the exam.
ICC, whose exams serve several cities and counties, allows references that are bound — originals, three-ring binders or stapled, with no photocopies of copyrighted material — notes in ink or highlighting, and permanently attached tabs that cannot be removed without destroying the page.
ICC also says most of its exams are open book but that open/closed status and allowed references vary by exam, so its catalog is the check.
One rule of thumb comes straight from ICC's candidate bulletin: you will not have time to look up every answer in an open-book exam, so you must know your references well — and there is no guessing penalty, so answer every question.
Open book is a lookup-speed test stacked on a knowledge test, which is why tabbing and indexing your book matters so much.
The business and law exam
The trade code is often only half the exam at the contractor level.
Candidates for a plumbing contractor licence commonly sit a second, separate exam on running a business.
California's CSLB qualifier passes a law and business exam plus the trade exam, both delivered by PSI.
Hawaii's contractor exam has two parts — Part I business and law, Part II trade knowledge — with a minimum of 75% on each part.
North Carolina's plumbing contractor exam is a 4.0-hour technical exam plus a 1.5-hour Business and Law exam; West Virginia's plumbing contractor licence requires the master plumber or plumbing exam plus the WV Business & Law exam; and both Utah plumbing contractor classes require the Utah Business and Law exam.
The content is what the name says.
New Mexico's Business and Law exam is 50 questions in 130 minutes, 75% to pass, open book, and based on the NASCLA Contractors Guide to Business, Law and Project Management (14th ed.).
Tennessee's is an open-book Tennessee Business and Law exam taken alongside the trade exam.
Nevada's Business and Law (CMS) exam is open book on the Construction Business and Law Manual for Nevada, while its trade exams are closed book except for code references listed in the content outline.
Louisiana folds the requirement into a course: its Business and Law requirement is a one-hour online course ending in an exam, with a $150 course fee.
Two boundaries matter.
First, individual worker licences usually skip it: North Carolina's Technician licence goes to a candidate who passed the technical exam but not the business and law exam — and a technician licence is not a contracting licence.
Second, passing it once rarely travels: Nevada can waive the trade exam for an experienced out-of-state qualifier but still requires the Nevada Business and Law exam, and Mississippi waives trade exams under its reciprocity agreements while the Mississippi Business and Law exam is always required.
At the master level it can sit inside the licence exam itself: Louisiana's master plumber exam has three written parts — the 2021 IPC/IRC, the Louisiana Sanitary Code, and business and law based on the NASCLA Louisiana guide.
Retakes, wait times and plumbing exam prep classes
Retake rules belong to the board, and they are stricter than most candidates expect.
Fail a North Carolina plumbing exam and you face a 90-day wait, a Re-Examination Application and a new fee — though a failed portion can be retaken within six months without retaking the portion you passed.
Utah's contractor exams through Prov allow three attempts spaced 30 days apart, then 180 days between further retakes.
Massachusetts allows failed plumbing exams to be retaken within 12 months.
The exam can also come back later in your career.
A South Carolina residential plumber licence lapsed more than three years requires re-examination, and North Carolina requires re-examination for a licence not renewed within three years of expiration.
Once you are licensed, the renewal calendar is cheaper than a second exam date.
A board-approved course can also be a prerequisite before you ever sit.
Illinois lets exam applicants qualify through four years as a licensed apprentice plumber or an approved plumbing course supervised by an Illinois licensed plumber.
Kentucky's journeyman requirement is two consecutive years as an apprentice, or one year plus a department-approved course, and Massachusetts requires master plumber candidates to complete the 110-hour Tier Five course unless they completed it as apprentices.
Louisiana's business and law requirement is itself a course with an exam at the end.
Beyond the courses boards require, we have no verified national data on commercial prep classes, so we will not rank any.
Your board's candidate bulletin or content outline is the prep roadmap: it names the portions, the code book and edition, and the passing score.
The portion-by-portion anatomy of the journeyman plumber test — written and practical portions, passing scores and the retake calendar — is covered in its own guide.
And if you are still mapping the ladder your exam sits on, our plumbing license requirements guide covers apprentice, journeyman and master, state by state.
Once you know who delivers your exam and which book it runs on, preparation is mostly lookup fluency: the tables, the schedules and the board's own rules.
And when the licence lands, plumber jobs across the country list the journeyman and master licences as the qualification that matters.
Career information, not legal advice. Exam vendors, code editions, open-book rules and retake waits are set by each licensing board and change; confirm yours with your state board — or the city or county where licensing is local — before you book.