- MD-MP is the combined Master Plumber/Gas Fitter exam run through the Maryland State Board of Plumbing and PSI.
- 100 scored questions in 240 minutes, split across 10 domains, with a 70% passing score.
- Gas Appliances and Piping carries 40 of 100 questions - nearly half the exam.
- Applications are online-only since March 31, 2025, and retesting is limited to once every 30 days.
What Is the MD-MP, Exactly?
MD-MP stands for the Maryland Master Plumber License Exam, the state credentialing test that Maryland journey plumbers must pass before they can hold a master plumber license. In Maryland, the master license is administered as a combined Master Plumber/Gas Fitter examination, meaning a single test covers both plumbing systems and gas piping/appliance knowledge rather than splitting them into two separate credentials.
This is a state regulatory exam, not a private industry certification. Passing it is the gateway to running your own plumbing business, pulling permits as a licensed master, and supervising journey plumbers and apprentices under Maryland law. If you're still mapping out what this exam covers at a high level, our companion piece What Is MD-MP? and the related MD-MP Meaning page walk through the terminology from a slightly different angle.
Who Administers the MD-MP
Two organizations run the show. The Maryland State Board of Plumbing, operating under the Maryland Department of Labor, sets eligibility rules, approves reference materials, and issues the actual master plumber license once you pass. PSI Examination Services is the testing vendor - they build and deliver the computer-based exam, manage scheduling, and enforce testing-center rules like what materials you're allowed to bring in.
Because the Board and PSI split responsibilities, some questions about eligibility belong to the Board's published requirements, while questions about test-day logistics belong to PSI's candidate bulletin. If you're not sure which prerequisites apply to you, the dedicated breakdown at MD-MP Requirements 2026: Eligibility, Prerequisites & How to Qualify untangles both sources in one place.
Exam Format and Question Style
The MD-MP is delivered as a computer-based, multiple-choice exam with 100 scored questions to be completed in 240 minutes. A passing score is 70%. PSI may also insert five to 10 unscored experimental questions into your test session - these are used to evaluate future exam items, and the time you spend on them does not count against your four-hour scored allowance, so don't panic if the test feels slightly longer than 100 questions.
It is an open-book exam, which changes how you should study. Permanent tabs, highlighting, and underlining inside your approved reference books are allowed. Handwritten notes, loose papers, and outside study guides are explicitly prohibited at the testing center. That means your prep time is better spent learning how to navigate the code books quickly than memorizing every clause from scratch.
The 10 MD-MP Content Domains
The 100 scored questions are distributed across 10 domains, and the allocation is far from even. Understanding this weighting is the single most important planning step before you open a study guide - a deep dive on this exact topic lives at MD-MP Exam Domains 2026: Complete Guide to All 10 Content Areas.
| 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 |
Domain 9: Gas Appliances and Piping
This single domain accounts for 40 of the 100 scored questions - nearly half the entire exam. It exists because the MD-MP is a combined Master Plumber/Gas Fitter test, not a plumbing-only exam.
- Gas piping sizing, sizing tables, and material selection
- Venting requirements for gas-fired appliances
- Appliance connection, shutoff placement, and code-required clearances
Domain 7: Drain, Waste, and Vent Systems
The second-largest domain at 13 questions. Expect coverage of pipe sizing, slope, venting configurations, and how DWV systems interact with fixtures and traps.
- Vent sizing and connection rules
- Trap arm distances and cleanout placement
- Interaction with backwater valves covered in Domain 3
Domain 6: Backflow Prevention
At 10 questions, backflow prevention is tested seriously - and it also has real-world teeth beyond the exam, since PSI requires candidates to hold a current approved 32-hour backflow prevention device testing certificate just to sit for the test.
- Device types and appropriate applications
- Testing and certification requirements
- Cross-connection control concepts
The remaining domains - Plumbing Fundamentals and Safety, Materials, Traps and Interceptors, Fixtures and Fittings, Water Supply Systems, Special Topics, and Plumbing Mathematics - carry fewer questions individually but still require solid command, since missing several small-domain questions can be the difference between passing and retesting. A full domain-by-domain study plan is covered in MD-MP Study Guide 2026: How to Pass on Your First Attempt.
Eligibility to Sit for the MD-MP
Standard eligibility for the MD-MP 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 requirement, PSI requires candidates to present a current approved 32-hour backflow prevention device testing certificate, work records documenting hours, and valid identification at application and/or check-in.
Since March 31, 2025, examination applications have been online-only - paper applications are no longer accepted. Build in extra lead time if you're gathering supervisor sign-offs or backflow certificates, since digital submission doesn't speed up the paperwork itself.
Key Takeaway
Don't wait until you're ready to schedule the exam to start your backflow certification - the 32-hour course requirement is a prerequisite for applying, not something you can complete after registering.
Registration, Fees, and Retesting
The MD-MP exam fee is $65 per attempt. This is separate from licensing fees: under the fee schedule effective July 1, 2025, both the initial master license and its renewal cost $87.50 each. Candidates who don't pass on their first attempt can retest, but retesting is allowed no more often than every 30 days, so plan your study runway with that cooldown in mind rather than assuming you can rebook the next week.
For a full breakdown of every fee a candidate is likely to encounter - exam fee, licensing fee, and renewal costs - see MD-MP Certification Cost 2026: Complete Pricing Breakdown. If you're trying to figure out testing windows and how the online-only application timeline affects when you can actually sit for the exam, MD-MP Exam Dates 2026: Testing Windows, Deadlines & Scheduling lays out the scheduling mechanics in detail.
After You Pass: Licensing and Insurance
Passing the exam is not the finish line - you must apply for the license within one year of passing, or you risk having to retest. Once issued, a Maryland master plumber license runs for two years, and general plumbing-license renewal carries no continuing education requirement, which is worth knowing if you're comparing this credential to other trades that mandate CE hours.
To be considered "insured-to-contract," Maryland requires master plumbers to carry at least $300,000 in general liability coverage and $100,000 in property-damage coverage per occurrence. This is a business-operations requirement layered on top of the license itself, not something tested on the exam, but it's essential to budget for if you plan to contract independently.
One more regional nuance: Baltimore County and the WSSC service area maintain their own separate licensing authorities, distinct from the statewide Board of Plumbing process. If you plan to work in either jurisdiction, verify their local requirements in addition to your state MD-MP credential.
Who Needs the MD-MP and Who Hires For It
The MD-MP matters most to journey plumbers who want to move up into ownership, supervisory, or contracting roles. Master plumbers pull permits, supervise apprentices and journey workers, and - because this is a combined license - sign off on gas piping and gas appliance work that a journey-only license typically can't cover independently.
Plumbing and mechanical contractors, property management companies with in-house maintenance divisions, and independent contracting businesses all look for the master designation when hiring for lead roles or when a business needs a named master to hold its license. If you're weighing whether pursuing this credential fits your career plans, Is the MD-MP Certification Worth It? Complete ROI Analysis 2026 and MD-MP Salary Guide 2026: Complete Earnings Analysis go deeper into the career upside, while MD-MP Jobs surveys the kinds of roles that specifically require the license.
Preparing for the MD-MP the Right Way
Because the exam is open-book but prohibits outside notes, your prep should focus on two things: knowing the material well enough to locate it fast in your approved 2018 IPC and IFGC references (subject to the 2024-code revisions being discussed in June 2026 board minutes), and practicing under realistic time pressure so 240 minutes for 100-plus questions feels comfortable rather than rushed.
Gas Appliances and Piping, plus Drain, Waste, and Vent Systems
- Start with Domain 9 since it's 40% of the exam by question count
- Layer in Domain 7 concepts, noting overlap with trap and vent rules
- Tab your code book sections for gas sizing tables and DWV requirements
Backflow Prevention and Water Supply Systems
- Review backflow device types alongside your 32-hour certificate coursework
- Cover Domain 5 water supply sizing and material rules
Remaining domains and full timed practice
- Finish Fundamentals, Materials, Traps/Interceptors, Fixtures, Special Topics, and Math
- Run full-length timed practice sets to build stamina for the 240-minute window
- Practice navigating your tabbed references quickly rather than re-reading full chapters
If you want a condensed reference for last-minute review, MD-MP Cheat Sheet 2026: One-Page Review of Must-Know Facts distills the key numbers - fees, timing, passing score, and domain weights - onto a single page. And for a candid assessment of how challenging the exam actually is relative to other trade licenses, How Hard Is the MD-MP Exam? Complete Difficulty Guide 2026 is worth reading before you commit to a study timeline. Once you're ready to test your knowledge under exam-like conditions, our practice test platform mirrors the domain weighting and question style described here so you're not just studying blind.
FAQ
MD-MP refers to 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. See What Does MD-MP Stand For? for more on the terminology.
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.
Gas Appliances and Piping, worth 40 of 100 questions, is by far the largest domain since the MD-MP is a combined plumbing and gas fitter exam. Drain, Waste, and Vent Systems at 13 questions is the next largest.
No. The exam is open-book for approved references with permanent tabs, highlighting, and underlining allowed, but handwritten notes, loose papers, and outside study guides are prohibited.
You must apply for the master plumber license within one year of passing the MD-MP, or you may need to retest before applying.