- Exam Snapshot: The Numbers That Matter
- Domain Weighting Cheat Sheet
- Registration and Fee Mechanics
- Eligibility Checklist
- Approved References and Open-Book Rules
- Gas Appliances and Piping: The Heavyweight Domain
- A Four-Week Domain-by-Domain Countdown
- After You Pass: Licensing and Insurance
- Jurisdiction Notes: Baltimore County and WSSC
- FAQ
- The exam is 100 scored multiple-choice questions in 240 minutes, passing score 70%.
- Gas Appliances and Piping carries 40 of 100 questions - nearly half your score.
- Applications are online-only, and the exam fee is $65 per attempt.
- Eligibility needs a journey license held 2+ years and 3,750 supervised hours under a master.
Exam Snapshot: The Numbers That Matter
If you only remember one section of this cheat sheet, make it this one. The Maryland Master Plumber License Exam (MD-MP) is administered through the Maryland State Board of Plumbing under the Maryland Department of Labor, with PSI Examination Services delivering the computer-based test. The selected examination is the combined Master Plumber/Gas Fitter format, which means gas-related content is baked into your score from question one.
- Format: Computer-based, multiple choice
- Scored questions: 100
- Time allowed: 240 minutes
- Passing score: 70%
- Unscored items: PSI may insert 5-10 experimental questions; time spent on these is excluded from your four-hour allowance
- Exam fee: $65 per attempt
Because unscored experimental questions look identical to scored ones, you cannot skip questions you assume are "just testing" - treat every item as real. For a deeper walkthrough of how these numbers translate into a study plan, see the MD-MP Study Guide 2026, and for a full explanation of the passing threshold itself, check MD-MP Passing Score 2026.
Domain Weighting Cheat Sheet
The MD-MP exam is built from ten content domains, and the official question allocations are dramatically uneven. Memorize this table before you memorize anything else - it tells you where to spend your study hours.
| 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, is worth as much as the next three largest domains combined. Domains 3, 4, and 8 together account for only 11 questions. A full breakdown of what each domain actually tests - not just the weight - lives in MD-MP Exam Domains 2026: Complete Guide to All 10 Content Areas.
Backflow Prevention (Domain 6, 10 questions)
This domain connects directly to a licensing prerequisite: PSI requires candidates to hold a current, approved 32-hour backflow prevention device testing certificate before they can sit for the exam. Study the same content you certified on - it reappears on the test.
- Device types and required air-gap/relief-valve configurations
- Installation clearances and testing sequences
Registration and Fee Mechanics
Registration for MD-MP is straightforward but has firm procedural rules that trip up unprepared candidates.
- Examination applications have been online-only since March 31, 2025 - there is no paper fallback.
- The exam fee is $65 per attempt, charged every time you sit, including retakes.
- Under the fee schedule effective July 1, 2025, the initial master license and each renewal are $87.50.
- If you fail, you may not retest sooner than every 30 days.
- Once you pass, you must apply for the license within one year of your passing date, or you risk having to retest.
These figures - and how they stack against total prep costs - are broken down further in MD-MP Certification Cost 2026: Complete Pricing Breakdown. If you want the scheduling side, including how the 30-day retest rule affects your calendar, see MD-MP Exam Dates 2026: Testing Windows, Deadlines & Scheduling.
Key Takeaway
Budget for the possibility of a retake. At $65 per attempt with a mandatory 30-day gap, a failed exam costs both money and calendar time - study the 40-question Gas Appliances and Piping domain hardest to avoid this.
Eligibility Checklist
Before you can even book a seat, standard eligibility requires:
- A journey (journeyman) plumber 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
- Documented work records and identification submitted to PSI
None of these are optional add-ons - PSI verifies work records and identification as part of the application review before you're approved to test. Candidates who are still accumulating supervised hours or who need the backflow certificate should start that process well before target-testing season. A full prerequisite walkthrough, including how supervised hours are documented, is available at MD-MP Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Approved References and Open-Book Rules
MD-MP is an open-book exam, but "open book" comes with strict limits candidates frequently misunderstand.
- Allowed: permanent tabs, highlighting, and underlining in your reference books
- Prohibited: handwritten notes, loose additional papers, and separate study guides
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 code editions are in flux. Always confirm the booked examination's reference edition directly with the board or PSI before purchasing books - don't assume last year's approved list still applies.
Gas Appliances and Piping: The Heavyweight Domain
With 40 of 100 questions, Domain 9 - Gas Appliances and Piping - is functionally its own mini-exam inside the MD-MP test, and the combined Master Plumber/Gas Fitter format makes this unavoidable. Candidates who under-prepare here often pass every other domain and still miss 70% overall because this single domain carries so much weight.
High-value topics to master under Domain 9 typically include:
- Gas pipe sizing methods and demand load calculations
- Venting requirements for gas-fired appliances
- Appliance connection, shutoff valve placement, and clearance requirements
- Combustion air supply and makeup air rules
Because this domain draws heavily from the IFGC, keep your fuel-gas code reference tabbed by chapter and cross-reference it constantly during practice questions. If you're unsure how difficult this domain feels relative to the rest of the exam, How Hard Is the MD-MP Exam? Complete Difficulty Guide 2026 discusses domain-level difficulty in more depth.
A Four-Week Domain-by-Domain Countdown
Generic study techniques only matter when mapped to MD-MP's specific weighting. Here's one way to sequence a final month of prep around the domain table above.
Foundation and Math
- Review Domain 1 (Fundamentals and Safety) and Domain 10 (Plumbing Mathematics) - smaller domains you can lock in quickly
- Practice pipe sizing and load calculations daily
Water Supply and Backflow
- Work through Domain 5 (Water Supply Systems) and Domain 6 (Backflow Prevention) - 18 combined questions
- Cross-check against your 32-hour backflow certification material
Gas Appliances and Piping Deep Dive
- Spend the majority of the week on Domain 9 alone - it's worth 40 questions
- Drill sizing tables, venting, and clearance rules with practice questions
DWV, Remaining Domains, and Full Simulation
- Finish Domain 7 (Drain, Waste, and Vent Systems), then Domains 2, 3, 4, and 8
- Run a full 240-minute timed practice exam to test pacing across all 100 questions
For a longer-horizon plan that starts further out, see the MD-MP Study Guide 2026: How to Pass on Your First Attempt. You can also run timed, domain-weighted practice sets on our main practice test platform to simulate the real question distribution before test day.
After You Pass: Licensing and Insurance
Passing the exam is not the finish line. A few post-exam mechanics matter as much as your score:
- You must apply for the license within one year of passing the exam.
- Licenses run two years from issuance, and general plumbing-license renewal carries no continuing education requirement.
- Renewal fees follow the same fee schedule as the initial license: $87.50.
- To operate as insured-to-contract, you need at least $300,000 general liability and $100,000 property-damage coverage per occurrence.
These aren't exam-day facts, but candidates who plan their career move immediately after certifying should read them now. If you're evaluating whether the license is worth pursuing at all given the cost and time commitment, Is the MD-MP Certification Worth It? Complete ROI Analysis 2026 and MD-MP Salary Guide 2026: Complete Earnings Analysis cover the career-side calculus, and MD-MP Jobs looks at who actually hires master-licensed plumbers in Maryland.
Jurisdiction Notes: Baltimore County and WSSC
One detail that surprises out-of-state or newly transferred candidates: Baltimore County and the WSSC (Washington Suburban Sanitary Commission) service area maintain separate licensing authorities from the statewide Maryland Board of Plumbing process. Holding your MD-MP master license does not automatically grant you working authority in every local jurisdiction - confirm requirements with the specific county or service area where you intend to contract before assuming statewide licensure covers you everywhere.
Key Takeaway
Master licensure through the state board is the credential tested by this exam, but local jurisdictions like Baltimore County and WSSC may layer on their own registration steps - plan for both.
If you're still getting oriented to the credential itself before diving into exam mechanics, background pieces like What Is MD-MP?, MD-MP Meaning, and MD-MP Certification cover the basics, while MD-MP Training outlines how candidates typically accumulate the 3,750 supervised hours before applying. You can also start practicing domain-weighted questions right away on the practice test homepage.
FAQ
There are 100 scored multiple-choice questions with a 240-minute time limit. PSI may add 5-10 unscored experimental questions, but the time spent on those doesn't count against your four hours.
Domain 9, Gas Appliances and Piping, carries 40 of the 100 questions - by far the largest single domain - followed by Domain 7 (Drain, Waste, and Vent Systems) at 13 and Domain 6 (Backflow Prevention) at 10.
No. The exam is open book, but only permanent tabs, highlighting, and underlining in approved reference books are allowed. Handwritten notes, loose additional papers, and separate study guides are prohibited.
Retesting is allowed no more often than every 30 days, and each attempt costs the $65 exam fee again.
A September 1, 2024 board-linked bulletin lists the 2018 IPC and 2018 IFGC as approved references, but June 2026 board minutes discuss 2024-code revisions. Confirm the exact reference edition for your booked exam before purchasing books.