- What Is A NJ-MP, Exactly?
- Who Issues It and Who Administers Testing
- The Three Examinations You Must Pass
- The 9 Domains of the Trade Examination
- Who Qualifies to Sit for the NJ-MP
- Fees, Application Costs, and Licensing Costs
- Reference Books You Can Bring Into the Exam
- Retake Rules and the Five-Year Clock
- Who Hires NJ-MP Holders
- Scheduling Your Prep Around the Domains
- Frequently Asked Questions
- NJ-MP is the New Jersey Master Plumber License Exam, overseen by the State Board of Examiners of Master Plumbers.
- Candidates take three PSI exams on one day: 100-question Trade, 50-question Business and Law, 25-question Practical.
- Passing requires 70% on each part: 70 of 100, 35 of 50, and 18 of 25 correct.
- Total PSI exam fees are $240; Board application adds $50 or $100 depending on prior registration.
What Is A NJ-MP, Exactly?
NJ-MP stands for the New Jersey Master Plumber License Exam - the credentialing exam a licensed journeyman plumber in New Jersey must pass to be legally recognized as a Master Plumber in the state. It is not a certificate you earn through a course or a private association; it is a state-regulated license administered under New Jersey's professional licensing framework and delivered through a third-party testing vendor. If you have seen "NJ-MP" used to describe something else, that is a different credential entirely - this article, and every fact in it, refers only to the New Jersey Master Plumber License Exam.
Passing the NJ-MP is the final gate between working as a journeyman under someone else's license and running your own plumbing business, pulling permits, and legally stamping plumbing work in New Jersey. For a plain-language walkthrough of the acronym itself, see What Is NJ-MP? and NJ-MP Meaning.
Who Issues It and Who Administers Testing
The license itself is issued by the New Jersey State Board of Examiners of Master Plumbers, part of the state's Division of Consumer Affairs. The Board sets eligibility rules, approves applicants, and issues the actual license once all exam parts are passed. Day-to-day test delivery, scheduling, and scoring are handled by PSI Services LLC, the testing provider contracted to administer the computer-based examinations.
This split matters practically: your application, fees, and eligibility documentation go through the Board, while your exam scheduling, candidate bulletin, and permitted reference materials come from PSI. Confusing the two is a common source of scheduling mistakes among first-time applicants.
The Three Examinations You Must Pass
Unlike single-exam trade credentials, becoming a New Jersey Master Plumber requires passing three separate PSI examinations, each with its own outline, question count, and passing threshold:
| Exam | Questions | Time | Passing Score | Fee |
|---|---|---|---|---|
| Trade Examination | 100 | 195 minutes | 70 correct (70%) | $87 |
| Business and Law | 50 | 130 minutes | 35 correct (70%) | $47 |
| Practical Examination | 25 | 130 minutes | 18 correct | $106 |
First-time candidates sit for all three on the same day, which adds up to 175 listed questions and 455 total testing minutes. That is a long testing day, and pacing across three distinct formats - open-book trade, closed-book law, and closed-book practical - is one of the biggest logistical challenges of the NJ-MP. For a deeper look at exactly what makes the day demanding, see How Hard Is the NJ-MP Exam? Complete Difficulty Guide 2026, and for the scoring math itself, see NJ-MP Passing Score 2026: Exactly What You Need to Pass.
Trade Examination
The Trade exam is open-book and computer-based, drawing from the 100-item PSI outline covering all nine domains of plumbing knowledge.
- You may bring your own 2021 National Standard Plumbing Code per the current PSI bulletin
Business and Law
This 50-question exam tests knowledge of New Jersey licensing law, contracting rules, and business practices using the NASCLA New Jersey guide, second edition, as the reference source.
- Requires 35 correct answers within 130 minutes
Practical Examination
The closed-book Practical exam has 25 questions split into Isometric Analysis (22 questions) and Figure Analysis (3 questions), with a PSI-supplied handout of NSPC tables you cannot write on.
- Requires 18 correct answers within 130 minutes
The 9 Domains of the Trade Examination
The 100-question Trade exam is built from PSI's published outline covering nine content domains. Materials, Uses, and Specifications is the largest domain by weight, meaning candidates should expect the deepest question coverage there. Note that Indirect Waste and Roof Drain Piping are subtopics folded into the Drains and Waste domain rather than standalone weighted areas.
- Domain 1: General Knowledge
- Domain 2: Materials, Uses, and Specifications
- Domain 3: Traps, Interceptors, and Backflow Prevention
- Domain 4: Plumbing Fixtures, Fixture Fittings, and Plumbing Appliances
- Domain 5: Water Supply Systems
- Domain 6: Drains and Waste
- Domain 7: Specialty Plumbing
- Domain 8: Safety
- Domain 9: Vent Systems
A full breakdown of what each domain covers, and how much of the exam each one likely represents, is available in NJ-MP Exam Domains 2026: Complete Guide to All 9 Content Areas. Understanding the domain structure before you build a study plan is one of the highest-leverage things a candidate can do - it tells you where the questions actually live.
Key Takeaway
Because Materials, Uses, and Specifications carries the most weight, allocate proportionally more review time there than to smaller domains like Figure Analysis-adjacent Specialty Plumbing content.
Who Qualifies to Sit for the NJ-MP
Board approval to test is not automatic. Candidates must be at least 21 years old and satisfy one of two pathways:
- A four-year U.S. Department of Labor-approved apprenticeship, or
- An eligible bachelor's degree in mechanical, plumbing, or sanitary engineering
Both pathways must include propane-services education and must be followed by one year of New Jersey journeyman plumbing experience with at least 1,200 practical hands-on hours logged. Once the Board approves your application, you have two years to sit for your first examination attempt, and five years to pass all required sections. The full eligibility checklist, including documentation tips, is covered in NJ-MP Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Fees, Application Costs, and Licensing Costs
The NJ-MP process involves several separate payments, and candidates are frequently surprised by how they stack:
- PSI exam fees: $87 (Trade) + $47 (Business and Law) + $106 (Practical) = $240 total
- Board application fee: $100 without prior registration, or $50 with prior registration
- Initial license fee: $160 in the first biennial year, or $80 in the second
- Biennial renewal: $160, requiring five approved continuing education credits including one hour of New Jersey law/rules (the first renewal period is exempt from this CE requirement)
For a complete line-item breakdown across the entire licensing journey, from application through renewal, see NJ-MP Certification Cost 2026: Complete Pricing Breakdown.
Reference Books You Can Bring Into the Exam
Because the Trade exam is open-book, what you're allowed to bring matters as much as what you study. Per the current PSI bulletin, candidates may bring their own copy of the 2021 National Standard Plumbing Code. Prior highlighting, underlining, and permanent tabs in that approved book are allowed; adding loose papers, temporary tabs, or writing anything during the test is prohibited.
It's worth noting that New Jersey adopted the 2024 New Jersey edition of the NSPC as state code, but that state-level code adoption does not automatically change which edition PSI lists as the permitted exam reference. Always check the PSI reference list tied to your specific booked exam date rather than assuming the newest code edition applies.
- Allowed in the exam room: your own 2021 National Standard Plumbing Code (per current bulletin), an on-screen calculator, and a permitted construction calculator
- Study-only, not exam-room references: Mathematics for Plumbers and Pipefitters, OSHA references, Modern Plumbing, and Plumbing Design and Installation
Key Takeaway
Confirm your permitted reference edition directly against the PSI bulletin for your exam date - don't assume the newly adopted state code edition is what you'll be tested against.
Retake Rules and the Five-Year Clock
If you fail one or more sections on your first sitting, New Jersey regulation (N.J.A.C. 13:32-2.4) allows you to retake failed sections up to two more times, with a required six-month wait between attempts. If you still haven't passed all sections after those additional attempts, you forfeit any previously passing scores and must retake every section from scratch.
Combined with the five-year window to pass everything from Board approval, this makes retake planning a real strategic consideration, not just a formality. A candidate who fails Business and Law on attempt one, for example, needs to factor a six-month gap into their five-year timeline before attempting it again.
Who Hires NJ-MP Holders
Holding a New Jersey Master Plumber license opens roles that a journeyman license cannot: pulling permits under your own name, owning or managing a licensed plumbing contracting business, supervising journeymen and apprentices on a job site, and bidding directly on residential and commercial plumbing contracts. Employers and clients that specifically seek Master Plumber-licensed professionals include plumbing contracting firms, mechanical contractors, property management companies needing a licensed responsible party, and municipalities requiring a licensed master plumber of record for certain projects.
For candidates weighing whether the investment in fees, study time, and the five-year approval window is worth it relative to career upside, Is the NJ-MP Certification Worth It? Complete ROI Analysis 2026 and NJ-MP Salary Guide 2026: Complete Earnings Analysis go deeper into the career-side comparison. If you're actively job hunting with a fresh license, NJ-MP Jobs covers where openings tend to concentrate.
Scheduling Your Prep Around the Domains
Because the Trade exam's 100 questions are spread unevenly across nine domains, an effective study calendar mirrors that weighting rather than splitting time evenly. Given that Materials, Uses, and Specifications is the largest domain, it deserves the most dedicated review blocks, followed by the domains most tied to daily field work: Water Supply Systems, Drains and Waste, and Vent Systems.
Materials, Uses, and Specifications + General Knowledge
- Work through material specification tables in your permitted NSPC copy
- Practice tabbing sections you'll need quickly on exam day
Water Supply, Drains and Waste, Vent Systems
- Focus on sizing and layout questions typical of these three interconnected domains
- Review indirect waste and roof drain piping as part of Drains and Waste, not separately
Fixtures, Traps/Backflow, Specialty Plumbing, Safety
- Cover the remaining trade domains
- Begin Business and Law review using the NASCLA New Jersey guide
Practical Exam Drills and Full Timed Run-Through
- Practice isometric analysis problems under closed-book conditions
- Simulate the full 455-minute testing day if possible
For a structured, week-by-week plan built specifically around these domain weights and the three-exam format, see NJ-MP Study Guide 2026: How to Pass on Your First Attempt. If you want a condensed, single-page review of the numbers in this article - fees, timing, passing scores - bookmark NJ-MP Cheat Sheet 2026: One-Page Review of Must-Know Facts.
Once you've got a handle on the domains and format, running realistic practice questions is the fastest way to find gaps before exam day. You can start building that familiarity now at NJ-MP Exam Prep's practice tests, and return to the main practice site as you move through each domain in your study plan.
Frequently Asked Questions
It's three separate PSI examinations taken on the same day for first-time candidates: the 100-question Trade exam, the 50-question Business and Law exam, and the 25-question Practical exam.
You need 70 correct answers out of 100 questions, which is 70%, within the 195-minute time limit.
No. The current PSI bulletin permits your own copy of the 2021 National Standard Plumbing Code with prior highlighting, underlining, and permanent tabs. Always verify the reference list tied to your specific exam date, since state code adoption doesn't automatically change PSI's listed reference.
Under N.J.A.C. 13:32-2.4, you can retake failed sections up to two more times with a required six-month wait between attempts. Failing to pass all sections within those attempts forfeits previously passing scores.
PSI Services LLC administers and scores the computer-based examinations, while the New Jersey State Board of Examiners of Master Plumbers reviews eligibility and issues the actual Master Plumber license.