ICC — the International Code Council — and IAPMO are two national organizations in the plumbing exam picture.
Neither is a licensing board: the licence comes from your state, city or county board, which decides whether an ICC or IAPMO exam counts.
The ICC plumbing exams our research verified are inspector-level certifications plus jurisdiction-adopted licence exams like Philadelphia's; IAPMO publishes the Uniform Plumbing Code and delivers exams for boards like Montana's.
Here is what each organization actually offers, and who accepts them.
Does ICC have a national standard journeyman or master plumber exam?
Search "ICC master plumber exam" or "national standard plumbing exam" and you are really asking two questions: does ICC publish its own journeyman- or master-level plumber certification, and do licensing boards use ICC exams for those licences?
Our research answers both, narrowly.
For plumbing, the certification exams our research documents in ICC's catalog sit at the inspector and plans-examiner level: P1 Residential Plumbing Inspector, P2 Commercial Plumbing Inspector, P3 Plumbing Plans Examiner and FG Fuel Gas Inspector, alongside the mechanical inspector exams M1, M2 and M3 — offered on the 2021 and 2024 code editions.
ICC's older content outlines put P1 and M1 at 60 multiple-choice questions in 2 hours, open book, and P2 at 50 questions in 2 hours, open book — outlines that in places predate 2015, so treat the current ICC catalog as the authority on formats.
At the journeyman and master level, the verified ICC exams are attached to a jurisdiction's own licence.
Philadelphia's journeyman plumber licence requires a passing score on the Journeyman Plumber Examination administered by the ICC — per ICC's March 2026 candidate bulletin for Philadelphia, 75 multiple-choice questions, closed book, 3 hours, $115, on the 2018 Philadelphia Plumbing Code.
Casper, Wyoming, licenses Apprentice, Journeyman and Master Plumbers, and its journeyman and master candidates need an approved ICC exam (G27-N/G28-N) plus a federally recognized apprenticeship or four years in a Casper-licensed shop.
The "National Standard" exam names our research verified are all on the mechanical side: Denver's Heating and Ventilating Journeyman certificate requires ICC exam F31 National Standard Journeyman Mechanical, and Pittsburgh's Mechanical Trade License requires the ICC National Standard Master Mechanical exam (F29 or W29, via Pearson VUE).
If your board's bulletin names an ICC exam for a plumber licence, the board defines what passing it is worth — Philadelphia's journeyman licence, for example, does not allow operating a business.
Check the exam name against your board's bulletin
What are IAPMO's plumbing exams?
IAPMO's verified role starts with the code.
It publishes the Uniform Plumbing Code (UPC), including state-specific editions for California, Idaho, Minnesota, South Dakota and Washington plus city codes such as Seattle's and Houston's.
Our research found no complete UPC-versus-IPC adoption map maintained by any primary source, so read that as the edition list we verified, not a national map.
When someone says "the IAPMO plumbing exam," they can mean one of two different things.
The first is IAPMO as the delivery vendor a board contracts.
In Montana, the Board of Plumbers approves your application and the exam is then scheduled through IAPMO, with exam fees paid directly to IAPMO — but what IAPMO delivers there is defined by the board's own exam sheet: the journeyman written exam is 100 multiple-choice questions on the 2021 UPC as amended plus board statutes and rules.
The second is a UPC-based exam delivered by somebody else entirely.
Hawaii's plumber exam is based on the Uniform Plumbing Code and administered by Prometric.
Nevada's NBOPE journeyman/master exam is based on the currently adopted UPC but pairs 50 open-book questions (2 hours) with 100 closed-book sizing questions (2 hours), passing at 75% or 113 cumulative points.
The code publisher and the exam vendor are two different decisions: the board names the exam and the vendor, while the jurisdiction adopts the code.
Which jurisdictions accept ICC and IAPMO exams?
Acceptance is decided where you licence.
Kansas designates ICC, IAPMO or Prometric exams as its standard plumbing competency exams at a 75% passing score — and because Kansas has no state plumbing contractor licence, its plumbing contractor licensing (and any bond or insurance requirement) is local, using the same designated exams.
The verified adopters make the pattern concrete.
Philadelphia delivers its journeyman plumber exam through the ICC.
Vermont's plumbing exams are ICC exams delivered through Prov — the state publishes a 2026 Prov bulletin and links ICC for plumbing testing, though the exact vendor split isn't confirmed, so read the bulletin.
Casper tests journeyman and master plumber candidates against approved ICC exams (G27-N/G28-N), and Cheyenne's Contractor Licensing Board sets exams for its qualified supervisor, plumbing and mechanical licences that are administered by ICC, the City, NICET and others.
ICC's footprint runs at the code level too, not just the exam level: Arkansas's Plumbing and Fuel Gas Codes are state editions published by the International Code Council.
Two organizations, two products, one rule — the adopting jurisdiction decides.
Our research did not compile a complete jurisdiction-by-jurisdiction acceptance list for either organization's exams, and we won't invent one: your board's candidate bulletin, or your city or county licensing office where licensing is local, is the list that counts.
For the vendor behind your state's test, our plumbing license exam guide maps who delivers what, board by board.
How do you register for an ICC or IAPMO plumbing exam?
The registration flows our research documents run through the licensing jurisdiction first: Montana's Board of Plumbers approves the application before any exam is scheduled, and Philadelphia's journeyman exam counts toward a licence that requires four years registered as a Philadelphia apprentice plumber.
The delivery channel differs by jurisdiction, so the board's candidate bulletin is your real registration document.
The known flows:
Apply to your licensing board first
Eligibility is the board's call. Montana's Board of Plumbers approves the application before any exam is scheduled; Philadelphia requires at least four years registered as a Philadelphia apprentice plumber (or equivalent out-of-area authorization) plus a passing score on its ICC-administered journeyman exam.Schedule through the channel your board names
Montana schedules exams through IAPMO, fees paid directly to IAPMO. Philadelphia's ICC-delivered journeyman exam books through Pearson VUE at $115. Vermont's plumbing exams are ICC exams delivered through Prov, though the exact vendor split isn't confirmed. Three boards, three channels.Confirm open or closed book, and the references
ICC says most of its exams are open book but that open/closed status and allowed references vary by exam — its catalog or your board's bulletin is the check. Philadelphia's ICC-delivered journeyman exam is closed book.Study the adopting jurisdiction's code edition
The exam sits on the jurisdiction's own code book: Philadelphia's runs on the 2018 Philadelphia Plumbing Code, Montana's on the 2021 UPC as amended. For ICC open-book exams, ICC's own advice is that you will not have time to look up every answer, so know your references — and there is no guessing penalty.
One caution travels across all of these: a bulletin from two years ago can be stale, and the current candidate bulletin is the source of record.
If you are still mapping the licence this exam feeds, our plumbing license requirements guide walks the apprentice-to-master ladder state by state — and when the licence lands, browse plumber jobs.
Career information, not legal advice. Exam names, vendors, fees and code editions are set by each licensing board — or the city or county where licensing is local — and change; confirm yours with the board before you apply or book.