- What MD-MP Actually Means
- Who Administers the MD-MP Exam
- Exam Format and Question Structure
- The 10 Domains Behind the Acronym
- Eligibility and Registration Mechanics
- Fees and Cost Schedule
- What You Can Bring Into the Test
- After You Pass: Licensing Timeline
- Local Jurisdiction Wrinkles
- Turning the Meaning Into a Study Plan
- FAQ
- MD-MP refers specifically to the Maryland Master Plumber License Exam, a combined Master Plumber/Gas Fitter test administered via PSI.
- The exam has 100 scored questions across 10 domains, delivered in 240 minutes, with a 70% passing score.
- Gas Appliances and Piping carries 40 of the 100 questions, making it the single most important domain by far.
- Applications are online-only since March 31, 2025, and retesting is capped at once every 30 days.
What MD-MP Actually Means
MD-MP stands for the Maryland Master Plumber License Exam - the state licensing test that a journey-level plumber in Maryland must pass to become a licensed master plumber. It is not a generic industry certification and it is not tied to any national trade body; it is a state credential issued through the Maryland State Board of Plumbing under the Maryland Department of Labor. The exam itself is delivered as a combined Master Plumber/Gas Fitter examination, meaning a single test covers both plumbing system knowledge and gas piping/appliance competency in one sitting.
Because "MD-MP" is a compact abbreviation, it's easy to confuse with similarly named credentials in unrelated fields. On this site, MD-MP always means the Maryland trade license exam described above - nothing else. If you found this page while researching plumbing licensure in Maryland, you're in the right place.
Who Administers the MD-MP Exam
Two entities sit behind the MD-MP name. The Maryland State Board of Plumbing, operating under the Maryland Department of Labor, sets eligibility rules, approves reference materials, and issues the license once you pass. PSI Examination Services is the third-party testing vendor that builds and proctors the computer-based exam, verifies your submitted documents, and enforces testing-day rules.
This two-party structure matters practically: your application and supervised-hours documentation go through the board's process, while your test-day logistics - scheduling, ID checks, reference material rules - are governed by PSI. If you want the full breakdown of what qualifies you to sit for the exam in the first place, see MD-MP Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Exam Format and Question Structure
The MD-MP is a computer-based, multiple-choice exam consisting of 100 scored questions to be completed in 240 minutes. PSI may insert five to 10 additional unscored experimental questions into your form; the time you spend on those doesn't count against your four-hour allowance, so the extra questions are essentially "free" from a time-budget perspective, though you won't know which ones they are.
A passing result requires a raw score of 70%. There is no partial credit weighting disclosed beyond the raw percentage, so the practical strategy is straightforward: answer every scored question, flag uncertain ones for review if the interface allows it, and manage your time against the heaviest-weighted domains first.
Key Takeaway
Because unscored experimental questions don't shrink your effective time, don't waste energy trying to guess which questions are "test" questions - just answer steadily through all of them.
For a deeper look at how difficult candidates actually find this pacing and content load, read How Hard Is the MD-MP Exam? Complete Difficulty Guide 2026, and for the exact scoring mechanics see MD-MP Passing Score 2026: Exactly What You Need to Pass.
The 10 Domains Behind the Acronym
The content of the MD-MP exam is organized into 10 domains, each with a fixed number of scored questions out of the 100-question total. Understanding this allocation is the single most useful thing you can do before opening a study guide, because it tells you exactly where your preparation time should go.
| Domain | Questions |
|---|---|
| 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 |
Gas Appliances and Piping
At 40 of 100 questions, this domain alone accounts for nearly half your score - a direct result of the exam's combined Master Plumber/Gas Fitter design.
- Sizing and sizing charts for gas piping runs
- Appliance venting and connection requirements
- Code-based limits drawn from the approved gas fitting reference
Drain, Waste, and Vent Systems
The second-largest domain at 13 questions, covering the core DWV knowledge every master plumber applies daily.
- Vent sizing and venting configurations
- Waste pipe slope and sizing rules
- Cleanout placement and access requirements
Backflow Prevention
Worth 10 questions, and also tied to a hard eligibility requirement - PSI requires proof of a current approved 32-hour backflow prevention device testing certificate just to sit for the exam.
- Device types and where each is required
- Cross-connection control principles
- Testing and certification documentation rules
A full walkthrough of every domain with the reasoning behind each question count is in MD-MP Exam Domains 2026: Complete Guide to All 10 Content Areas.
Eligibility and Registration Mechanics
Standard eligibility for the MD-MP exam requires holding a journey plumber license for at least two years and completing 3,750 supervised training hours under a licensed master plumber. On top of that experience threshold, PSI's registration process requires:
- A current, approved 32-hour backflow prevention device testing certificate
- Documented work records showing your supervised hours
- Valid identification matching your application
Since March 31, 2025, applications for this exam have been online-only - there is no paper application path anymore. Build this into your planning timeline, since document gathering (work records especially) tends to take longer than candidates expect. For the full eligibility checklist and how to assemble your paperwork, see MD-MP Requirements 2026, and for scheduling windows and deadlines check MD-MP Exam Dates 2026: Testing Windows, Deadlines & Scheduling.
Fees and Cost Schedule
Under the fee schedule effective July 1, 2025, the MD-MP exam costs $65 per attempt. If you don't pass on your first try, that $65 applies each time you retest - there is no discounted retake rate. Once you pass, the initial master license fee is $87.50, and renewal is also $87.50 under the same schedule.
Licenses run for two years from the date of issuance, and general plumbing-license renewal carries no continuing education requirement - a detail worth knowing if you're comparing Maryland's structure against other states' trade licenses. A complete breakdown of every fee a candidate will encounter, from exam attempt to license renewal, is covered in MD-MP Certification Cost 2026: Complete Pricing Breakdown.
What You Can Bring Into the Test
The MD-MP exam is open book, but the rules around what "open book" means are specific. A board-linked bulletin dated September 1, 2024 lists the 2018 IPC and 2018 IFGC among the approved candidate-supplied references. You're allowed to bring permanent tabs, and you may highlight and underline directly in your code books. What's prohibited: handwritten notes, additional loose papers, and separate study guides brought into the test room.
One important caveat: June 2026 board minutes discuss revisions tied to the 2024 code cycle. If your scheduled exam date falls anywhere near a code transition period, confirm the exact reference edition tied to your specific booked exam before you buy books - buying the wrong edition wastes both money and study time.
Key Takeaway
Tab and highlight your code books early so navigation becomes automatic - with 100 questions in 240 minutes, fumbling through an un-tabbed reference book costs real time.
After You Pass: Licensing Timeline
Passing the exam is not the end of the process. You must apply for the license within one year of passing - miss that window and you may need to retest. Once issued, the master plumber license is valid for two years before renewal is required.
If you don't pass on your first attempt, Maryland allows retesting no more often than every 30 days. That cooling-off period is worth planning around: it's enough time to seriously revisit your weakest domain (almost always Gas Appliances and Piping, given its weight) without losing momentum entirely. For a data-grounded look at how attempts and outcomes actually play out, see MD-MP Pass Rate 2026: What the Data Shows.
Local Jurisdiction Wrinkles
Passing the state MD-MP exam and holding a master plumber license doesn't automatically clear every local hurdle in Maryland. Baltimore County and the WSSC service area (Washington Suburban Sanitary Commission) each maintain their own separate licensing authorities layered on top of the state credential. If your intended work territory touches either of these jurisdictions, plan to research their specific registration steps in addition to the state board process - don't assume state licensure alone is sufficient everywhere in Maryland.
Turning the Meaning of MD-MP Into a Study Plan
Once you understand what MD-MP actually tests - a combined plumbing and gas fitting exam weighted heavily toward one domain - your study plan should mirror that weighting rather than treating all 10 domains equally.
Gas Appliances and Piping
- Work through sizing tables and appliance venting rules first, since this domain alone is 40% of your score
- Cross-reference every practice question against your tabbed 2018 IFGC
Drain, Waste, and Vent Systems + Backflow Prevention
- These two domains combine for 23 questions - the second-heaviest block on the test
- Review your backflow prevention certificate material alongside this section since it's tested directly
Remaining Domains and Full Timed Runs
- Cover Water Supply Systems, Plumbing Mathematics, Materials, Fixtures, Fundamentals, and Special Topics
- Run full 240-minute practice sets to build stamina against the 100-question format
This sequencing isn't generic exam advice - it follows directly from the official question allocation. For a step-by-step first-attempt strategy built around this same weighting, see MD-MP Study Guide 2026: How to Pass on Your First Attempt, and for quick-reference review material close to test day, use MD-MP Cheat Sheet 2026: One-Page Review of Must-Know Facts. You can also run timed practice questions on our main practice test platform to get comfortable with the exam's pacing before test day.
Frequently Asked Questions
MD-MP stands for the Maryland Master Plumber License Exam - the combined Master Plumber/Gas Fitter test administered through the Maryland State Board of Plumbing and PSI Examination Services. For a broader overview, see What Does MD-MP Stand For?
Maryland's selected examination is a combined Master Plumber/Gas Fitter test, and Gas Appliances and Piping is the single largest domain at 40 of 100 questions, so gas fitting knowledge is essential, not optional.
There are 100 scored multiple-choice questions to complete in 240 minutes, with a possible five to 10 additional unscored experimental questions whose time doesn't count against your allowance.
Yes, the exam is open book. Permanent tabs, highlighting, and underlining are allowed in approved references like the 2018 IPC and 2018 IFGC, but handwritten notes, loose papers, and outside study guides are not permitted.
Retesting is allowed no more often than every 30 days, and each attempt costs $65 under the fee schedule effective July 1, 2025.