- What the MD-MP Exam Actually Covers
- Registration, Fees, and Deadlines
- Domain-by-Domain Study Priorities
- Why Gas Appliances and Piping Deserves Extra Time
- Exam Format, References, and What You Can Bring
- Eligibility Checklist Before You Apply
- A Six-Week Study Timeline Built Around the Domains
- After You Pass: Licensing, Insurance, and Renewal
- FAQ
- The exam is 100 scored questions in 240 minutes; you need 70% to pass.
- Gas Appliances and Piping accounts for 40 of 100 questions - nearly half your score.
- Applications are online-only, and PSI requires a current 32-hour backflow prevention certificate.
- Retesting is capped at once every 30 days, so first-attempt preparation matters.
What the MD-MP Exam Actually Covers
The Maryland Master Plumber License Exam - administered through PSI Examination Services on behalf of the Maryland State Board of Plumbing, Maryland Department of Labor - is the combined Master Plumber/Gas Fitter examination. That combination matters: you are not just being tested on pipe sizing and fixture installation, you're also being tested on gas appliance venting, gas piping sizing, and gas system safety in the same sitting. Candidates who prep only for "plumbing" and treat gas fitting as an afterthought are the ones who run out of confidence halfway through the exam.
This guide is part of a broader set of resources on this MD-MP study guide series. If you haven't yet reviewed how the ten content areas are structured, start with the complete guide to all 10 content areas before diving into a study plan - it will save you from over-preparing for low-weight domains and under-preparing for the ones that actually decide your score.
Registration, Fees, and Deadlines
Since March 31, 2025, all examination applications must be submitted online - there is no paper application path anymore. Build this into your timeline: gather your journey-license documentation, training hour logs, and backflow certificate before you sit down to apply, because the portal will expect everything up front.
- Exam fee: $65 per attempt.
- Initial master license and renewal: $87.50 each, under the fee schedule effective July 1, 2025.
- Retest limit: No more often than every 30 days if you don't pass.
- Post-pass deadline: You must apply for the license within one year of passing, or you risk having to retest.
A full cost picture - including how these fees stack against license terms - is laid out in the complete pricing breakdown. If you're weighing whether the investment of time and money is worth it relative to what a master license opens up for you professionally, the ROI analysis and the earnings analysis are useful companion reads.
Key Takeaway
Because retesting is capped at once every 30 days, and because each attempt costs $65, a scattered "I'll just retake it" mindset is expensive and slow. Treat the first attempt as the only attempt you're planning for.
Domain-by-Domain Study Priorities
The exam's 100 scored questions are distributed unevenly across ten domains. Understanding this distribution is the single highest-leverage thing you can do before opening a code book, because it tells you exactly where your study hours will pay off.
| Domain | Question Count |
|---|---|
| 1. Plumbing Fundamentals and Safety | 5 |
| 2. Materials, Uses, and Specifications | 6 |
| 3. Traps, Interceptors, and Backwater Valves | 4 |
| 4. Plumbing Fixtures, Fixture Fittings, and Plumbing Appliances | 4 |
| 5. Water Supply Systems | 8 |
| 6. Backflow Prevention | 10 |
| 7. Drain, Waste, and Vent Systems | 13 |
| 8. Special Topics | 3 |
| 9. Gas Appliances and Piping | 40 |
| 10. Plumbing Mathematics | 7 |
Notice how much is riding on just three domains: Gas Appliances and Piping (40), Drain, Waste, and Vent Systems (13), and Backflow Prevention (10). Together those three account for 63 of the 100 scored questions. Domains like Special Topics (3), Traps, Interceptors, and Backwater Valves (4), and Plumbing Fixtures, Fixture Fittings, and Plumbing Appliances (4) matter, but spending equal hours on all ten domains is a strategic mistake.
Backflow Prevention
This domain is worth 10 questions on its own, and it's also an eligibility gatekeeper: PSI requires a current approved 32-hour backflow prevention device testing certificate before you can even sit for the exam. Study this domain twice - once for your certificate coursework, and again specifically for exam-style questions on device types, testing procedures, and cross-connection control.
- Know the difference between testable and non-testable assemblies
- Understand where backflow devices are required by fixture and system type
Why Gas Appliances and Piping Deserves Extra Time
At 40 of 100 questions, Gas Appliances and Piping is not just the largest domain - it is nearly four times larger than the next-biggest domain. If you fail this exam, statistically it will be because of gaps here, not because of a weak answer on plumbing mathematics.
Gas Appliances and Piping
Because this is a combined Master Plumber/Gas Fitter exam, expect deep coverage of gas piping sizing methods, appliance venting requirements, gas meter and regulator placement, shutoff valve locations, and appliance connection standards.
- Practice sizing gas piping systems by hand, not just recognizing the right formula
- Review venting categories and clearance requirements for common gas appliances
- Memorize where shutoff valves are required relative to appliances and meters
Because this domain carries so much weight, it deserves its own dedicated review pass separate from your general code-book reading. Treat it as a mini-exam within the exam.
Exam Format, References, and What You Can Bring
The exam is delivered computer-based: 100 scored multiple-choice questions in a 240-minute window, with a 70% passing score. PSI may also insert five to 10 unscored experimental questions into your test session - you won't know which questions those are, but PSI's own time for those items is excluded from your four-hour allowance, so the clock isn't working against you because of them.
This is an open-book exam, but "open book" has strict limits:
- Allowed: permanent tabs, highlighting, and underlining in your approved references.
- Not allowed: handwritten notes, additional loose papers, or separate study guides brought into the testing room.
A board-linked bulletin dated September 1, 2024 lists the 2018 IPC and 2018 IFGC among the approved candidate-supplied references. However, June 2026 board minutes discuss 2024-code examination revisions, so the reference edition tied to your specific exam date may differ. Confirm the exact edition before you buy or tab a code book - tabbing the wrong edition wastes hours and can leave you fumbling for section numbers on exam day.
Because scoring hinges on a fixed 70% threshold rather than a curve, understanding exactly how that number is calculated against 100 scored items is worth reviewing on its own - see the passing score breakdown for the exact math. And if you're still deciding when to schedule, the testing windows and scheduling guide covers deadlines around applications and retest spacing.
Eligibility Checklist Before You Apply
Standard eligibility for the Master Plumber/Gas Fitter exam requires:
- A journey license held for at least two years
- 3,750 supervised training hours worked under a licensed master plumber
- A current, approved 32-hour backflow prevention device testing certificate
- Work records and identification submitted through the online-only application process
These aren't formalities PSI checks casually - incomplete documentation is one of the most common reasons applications stall. Review the full eligibility, prerequisites, and qualification guide before you submit anything, especially if your training hours were split across multiple employers or jurisdictions.
A Six-Week Study Timeline Built Around the Domains
Generic study techniques - spaced repetition, timed practice blocks, teaching concepts back out loud - work best when they're mapped directly onto the MD-MP domain weights rather than applied evenly across all ten topics. Here's one way to sequence six weeks of preparation so your heaviest-weighted domains get the most repetition before test day.
Foundations
- Review Plumbing Fundamentals and Safety and Materials, Uses, and Specifications
- Confirm your approved reference edition and start tabbing your code books
Gas Appliances and Piping
- Dedicate two full weeks to sizing exercises, venting categories, and shutoff placement
- Work practice questions daily since this domain alone is 40% of your score
Drain, Waste, and Vent Systems and Backflow Prevention
- Pair these two domains since both hinge on system layout and code cross-references
- Re-check your backflow certificate is current and matches PSI's application requirements
Water Supply Systems and Plumbing Mathematics
- Focus on calculation-heavy questions; practice under timed conditions
- Review Traps, Interceptors, and Backwater Valves and Plumbing Fixtures, Fixture Fittings, and Plumbing Appliances briefly
Full Simulation and Special Topics
- Take a full 240-minute practice run to build stamina against the real time limit
- Clean up Special Topics and any remaining weak spots identified in practice
For a compressed version of everything above that you can review the night before your exam, keep the one-page review of must-know facts handy. And if you want a broader sense of how demanding this exam is compared to what candidates expect going in, read the complete difficulty guide.
After You Pass: Licensing, Insurance, and Renewal
Passing the exam is not the finish line - it's a one-year clock. You must apply for the actual license within one year of passing, or you risk having to retest. Once issued, the license runs for two years, and general plumbing-license renewal has no continuing education requirement, which is worth knowing if you're comparing this credential to trades that mandate ongoing CE hours.
If you plan to work as an insured-to-contract master plumber, you'll need at least $300,000 in general liability coverage and $100,000 in property-damage coverage per occurrence. Build this into your post-exam budget alongside the $87.50 initial license fee - it's a real cost of actually using the license commercially, not just holding it.
Employers across residential, commercial, and municipal plumbing work look specifically for this state credential when hiring for lead and supervisory roles. If you're mapping out where a Master Plumber license fits into your career path, the job market overview and general training pathway guide are good next stops. For quick definitional context to share with coworkers or apprentices, see what MD-MP is, what the term means, and what the acronym stands for.
Once you're ready to test your recall against exam-style questions across all ten domains, practicing on realistic timed sets on the main practice test platform is one of the most direct ways to find your weak spots before test day rather than after it. Running a full-length simulation on the practice test site at least once before your real exam date will also help you calibrate your pacing against the 240-minute limit.
FAQ
The exam has 100 scored multiple-choice questions with a 240-minute time limit. PSI may add five to 10 unscored experimental questions, but their response time is excluded from your four-hour allowance.
Gas Appliances and Piping, which accounts for 40 of the 100 scored questions - by far the largest domain. Drain, Waste, and Vent Systems (13 questions) and Backflow Prevention (10 questions) are the next priorities.
No. The exam is open book with permanent tabs, highlighting, and underlining allowed in approved references, but handwritten notes, loose papers, and separate study guides are prohibited.
Retesting is allowed no more often than every 30 days, and each attempt costs $65, so thorough first-attempt preparation is the more efficient path.
A September 1, 2024 bulletin lists the 2018 IPC and 2018 IFGC as approved references, but June 2026 board minutes discuss 2024-code revisions. Confirm the exact edition tied to your scheduled exam date before buying or tabbing books.