Plumbing Contractor License Exam Guide (2026)

The U.S. plumbing contractor exam tests fixture-unit sizing, drain-waste-vent (DWV) layout, water supply distribution, backflow prevention, water heaters, and fuel gas piping - all referenced from the code your state has adopted. About 35 states use the International Plumbing Code (IPC); the rest (notably California, Oregon, Washington, Idaho, Nevada, and parts of the Midwest) use the Uniform Plumbing Code (UPC). The two codes diverge enough that the wrong code book is the single most common reason candidates fail.

~80 questionstypical exam length
4 hourstime limit (varies by state)
70% to passtypical scaled score

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How states license plumbing contractors

45 of 51 jurisdictions license plumbing contractors at the state level - more than any other trade. Plumbing licensing usually has multiple tiers: journeyman, master, and contractor. The master plumber is a personal credential; the plumbing contractor license is for the business. Most states require a master plumber to be the qualifying individual on the company license. Reciprocity is unusually common in plumbing - 18 states have written reciprocity agreements with at least one neighbor. Pick your state below for the exact tier structure, master-to-contractor pathway, and accepted reference editions.

Approved code books and references

Every plumbing contractor exam is open-book with state-approved references. The primary reference is the International Plumbing Code (IPC) or Uniform Plumbing Code (UPC); supplementary references vary by state.

IPC (International Plumbing Code) - used by ~35 states - 2018, 2021, or 2024 edition depending on adoption
UPC (Uniform Plumbing Code) - used by CA, OR, WA, ID, NV, MN, and several Midwest states - significantly different from IPC
IFGC or Fuel Gas Code - fuel gas piping, appliance venting, and combustion-air rules
IECC - fixture-flow and water-heating efficiency rules

Confirm the exact editions in your state's current candidate information bulletin - states usually lag the newest code cycle by one or two editions. Our code-book tabbing guide walks through how to set up tabs so you can hit a section in under 30 seconds under exam pressure.

What the Plumbing contractor exam tests

Fixture-unit sizing (DFU and WSFU). Demand calculations for drainage (DFU) and water supply (WSFU). Memorize the per-fixture values for the most common fixtures so you can size a building service in under 90 seconds.
Drain, waste, and vent (DWV) systems. Branch sizing, fixture vent distance limits, wet venting (IPC only - prohibited in most UPC jurisdictions), and circuit/loop vents. UPC and IPC venting rules are NOT interchangeable.
Water supply and distribution. Water service sizing (Appendix E in IPC, Chart A 5.3 in UPC), pressure-loss calculations, hot-water recirculation, and mixing-valve requirements.
Backflow prevention and cross-connection control. Air gaps, atmospheric vacuum breakers, RPZ assemblies, and double-check valve assemblies. Know which fixtures and connections require which device, because exams love this topic.
Water heaters and pressure relief. Temperature/pressure relief valve placement, expansion tanks on closed systems, sediment trap rules on gas heaters, and seismic strapping (UPC).
Fuel gas piping and venting. Pipe sizing tables (longest-run vs. branch-length methods), draft-hood and direct-vent appliance categories, and combustion-air supply calculations.
Storm drainage. Sizing of horizontal storm drains and vertical conductors, roof drains, and combined sewers where still permitted.
Specialty plumbing systems. Medical gas (NFPA 99), commercial-kitchen grease interceptors, and dental-office isolation valves. These rarely exceed 5-10 percent of the exam but they are easy points if you have read the chapter.

Plumbing contractor exam study plan

Confirm whether your state uses IPC or UPC before you buy a code book. Many candidates waste a month studying the wrong code.
Tab the venting, sizing, and water-supply chapters first - between them they drive 60% of exam content.
Build a memorized fixture-unit cheat sheet for the 10 most common fixtures - it pays back hours of lookup time.
Take a 25-question DWV-only drill, then a 25-question water-supply-only drill. Track which sub-topics you missed and re-read those chapters.
Two weeks out, take a full-length timed exam. If you scored under 75%, slow down and rebuild your weak topics rather than scheduling.

See our 30-day crunch plan for a compressed version, or our full exam prep guide for the extended one.

Pick your state for plumbing contractor licensing details

Each state has its own plumbing contractor license tiers, fees, experience requirements, and reciprocity agreements. Pick your state below for the exact licensing board, application checklist, accepted code editions, and state-specific topics that go beyond the national code references covered on this page.

New England

Cold winters, nor'easters, and historic preservation challenges define construction in these states.

Mid-Atlantic

Dense urban development, historic buildings, and freeze-thaw cycles present unique challenges.

Southeast

Hurricane exposure, humidity, and termite risks dominate construction concerns. Several states accept NASCLA.

Gulf Coast

Hurricane-resistant construction, flood zones, and strict wind codes are essential knowledge.

Midwest & Great Lakes

Extreme temperature swings, heavy snow loads, and tornado risks influence building practices.

Great Plains

Severe weather, tornadoes, and wide temperature ranges define construction in these states.

Mountain West

High altitude, heavy snow, wildfires, and seismic activity create unique building challenges.

Southwest

Extreme heat, flash floods, expansive soils, and desert construction techniques are emphasized.

West Coast

Seismic design, wildfires, and some of the nation's strictest building codes apply.

Alaska & Hawaii

Extreme climates - arctic cold or tropical conditions - require specialized construction knowledge.

All 51 state licensing guides →

Plumbing practice questions and timed exams

Our timed practice exams use the same style, difficulty curve, and code references you will see on test day. Each attempt gives you an instant score, detailed rationales with code-section citations, and a weak-topic map so you know exactly where to focus next.

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Plumbing contractor exam FAQ

IPC or UPC - which plumbing code is on my exam?

Check your candidate information bulletin first. About 35 states use the IPC; California, Oregon, Washington, Idaho, Nevada, Minnesota, and several Midwest states use the UPC. The fixture-unit values, venting rules, and water-heater requirements differ enough that studying the wrong code will almost certainly cause you to fail.

How many questions are on the plumbing contractor exam?

Most plumbing contractor exams run 70 to 100 questions over 3 to 4 hours, with a 70 percent passing score. State exams that combine the journeyman and master sections can run to 6 hours and 200 questions.

Do I need to be a master plumber before I can apply for a plumbing contractor license?

In most states, yes - the contractor license requires a master plumber to be the qualifying individual on the business application. The few exceptions allow a journeyman plumber with enough documented years of experience to qualify the company.

Is the plumbing contractor exam open-book?

Yes. The IPC (or UPC), the local fuel gas code, the IECC, and OSHA 1926 are typically allowed - all tabbed and highlighted only, no sticky notes or loose inserts.

How is the plumbing contractor exam scored?

Almost every state uses a scaled passing score around 70 percent. Some break the exam into multiple modules (water supply, DWV, fuel gas) that must each be passed independently.