- What the MD-MP Certification Actually Covers
- Who Administers MD-MP and Why It Matters
- Eligibility: Journey Time, Hours, and Backflow Certification
- Exam Format, Fees, and Scoring
- The 10 Domains and Question Allocations
- Open-Book References and Allowed Materials
- After You Pass: Licensing, Renewal, and Insurance
- Scheduling Your Prep Around the Domain Weights
- Frequently Asked Questions
- MD-MP is the combined Master Plumber/Gas Fitter exam: 100 scored questions in 240 minutes, 70% to pass.
- Gas Appliances and Piping alone carries 40 of 100 questions - the largest domain by far.
- Eligibility requires two years as a journey licensee plus 3,750 supervised training hours.
- Exam fee is $65 per attempt; applications have been online-only since March 31, 2025.
What the MD-MP Certification Actually Covers
The Maryland Master Plumber License Exam (MD-MP) is the credentialing exam administered through the Maryland State Board of Plumbing, part of the Maryland Department of Labor, with delivery handled by PSI Examination Services. The exam Maryland candidates sit for is specifically the combined Master Plumber/Gas Fitter examination - meaning a single test covers both plumbing systems and gas fitting knowledge rather than splitting them into separate credentials.
This matters for how you prepare. A candidate who studies plumbing fundamentals but treats gas work as an afterthought will be surprised by how much of the exam is dedicated to gas appliances and piping. We break down exactly how the content is weighted in the MD-MP Exam Domains 2026: Complete Guide to All 10 Content Areas, but the short version is: this is not a generic plumbing test, and it rewards candidates who study it as its own exam.
Who Administers MD-MP and Why It Matters
Because the Maryland State Board of Plumbing owns the licensing requirements while PSI Examination Services delivers the computer-based test, candidates deal with two sets of rules simultaneously. The board sets eligibility, fees, and renewal policy. PSI sets test-day logistics - what you can bring, how experimental questions are handled, and how scores are reported.
This split administration explains why some candidates get confused about documentation. PSI's own candidate bulletin requires proof of a current approved 32-hour backflow prevention device testing certificate, along with work records and identification, separate from anything the board reviews during licensing. If you're unclear on how these pieces fit together, the MD-MP Requirements 2026: Eligibility, Prerequisites & How to Qualify guide walks through each document you'll need before you can even sit for the test.
It's also worth noting that Baltimore County and the WSSC service area maintain separate licensing authorities from the statewide board. If you plan to work in those jurisdictions, confirm locally whether additional licensing steps apply beyond the state Master Plumber credential.
Eligibility: Journey Time, Hours, and Backflow Certification
Standard eligibility for the MD-MP exam requires:
- A journey 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 submitted to PSI
- Supporting work records and identification documents
Applications have been online-only since March 31, 2025, so paper submissions are no longer accepted. Build in time to gather your supervised-hours documentation before your intended application date - missing paperwork is one of the most common reasons candidates delay their exam date. For a full walkthrough of the qualification path, see MD-MP Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Key Takeaway
Start collecting your 3,750-hour supervised training documentation early. The board reviews these records as part of eligibility, and incomplete files are a common cause of delayed exam scheduling.
Exam Format, Fees, and Scoring
The MD-MP exam is computer-based and multiple choice, consisting of 100 scored questions to be completed within 240 minutes. The passing score is 70%. PSI may insert five to 10 additional unscored experimental questions into the test; these do not count toward your score, and the time allowance for the four-hour window excludes response time for those experimental items - meaning your effective time budget for scored content isn't shortened by their presence.
Fee structure, per the schedule effective July 1, 2025:
| Item | Cost |
|---|---|
| Exam attempt fee | $65 per attempt |
| Initial master license | $87.50 |
| License renewal | $87.50 |
For a complete cost breakdown including how these fees stack up across an initial licensing cycle, read MD-MP Certification Cost 2026: Complete Pricing Breakdown. And if you're wondering exactly what 70% means in practice - how many questions you can miss per domain - the MD-MP Passing Score 2026: Exactly What You Need to Pass article covers that in detail.
The 10 Domains and Question Allocations
MD-MP content is organized into 10 domains, and the official question counts out of 100 are far from evenly distributed. Understanding this weighting is the single most important strategic decision you'll make in your prep.
Domain 1: Plumbing Fundamentals and Safety - 5 questions
Covers core safety practices and foundational plumbing principles that underpin the rest of the exam.
Domain 2: Materials, Uses, and Specifications - 6 questions
Focuses on correct material selection and specification requirements across plumbing applications.
Domain 3: Traps, Interceptors, and Backwater Valves - 4 questions
Tests knowledge of drainage protection components and where each device type is required.
Domain 4: Plumbing Fixtures, Fixture Fittings, and Plumbing Appliances - 4 questions
Covers fixture installation requirements, fitting compatibility, and appliance connections.
Domain 5: Water Supply Systems - 8 questions
Addresses distribution, sizing, and supply system design principles.
Domain 6: Backflow Prevention - 10 questions
Given that PSI already requires a 32-hour backflow testing certificate for eligibility, this domain rewards candidates who treat backflow devices as a distinct specialty area, not a side note.
Domain 7: Drain, Waste, and Vent Systems - 13 questions
One of the heavier domains - covers DWV layout, venting requirements, and waste system design.
Domain 8: Special Topics - 3 questions
A smaller, catch-all domain; don't over-invest study time here relative to its weight.
Domain 9: Gas Appliances and Piping - 40 questions
By far the largest domain, accounting for 40% of the entire scored exam. This reflects the combined Master Plumber/Gas Fitter scope of the test. Candidates who under-prepare gas piping sizing, appliance venting, and code requirements put their entire pass at risk.
- Prioritize this domain above all others in your study schedule
Domain 10: Plumbing Mathematics - 7 questions
Covers calculations relevant to sizing, pressure, and layout - practice problems here, don't just read theory.
For a domain-by-domain study strategy that mirrors this exact weighting, see MD-MP Exam Domains 2026: Complete Guide to All 10 Content Areas. If you want a condensed, one-page version of these facts for last-minute review, the MD-MP Cheat Sheet 2026: One-Page Review of Must-Know Facts is built for that purpose.
Open-Book References and Allowed Materials
The MD-MP exam is open book, but the rules on what you can bring are specific. Permanent tabs, highlighting, and underlining in your reference books are allowed. Handwritten notes, additional loose papers, and outside study guides are prohibited during the test.
A board-linked bulletin dated September 1, 2024 lists the 2018 IPC (International Plumbing Code) and 2018 IFGC (International Fuel Gas Code) among the approved candidate-supplied references. However, June 2026 board minutes discuss code revisions tied to the 2024 code cycle - so before you purchase or tab any code book, confirm the exact edition tied to your scheduled examination. Booking with the wrong edition of tabbed references wastes both money and prep time.
After You Pass: Licensing, Renewal, and Insurance
Passing the exam is not the finish line. You must apply for the master license within one year of passing the exam, or you risk having to retest. Once issued, licenses run for two years, and general plumbing-license renewal carries no continuing education requirement - a detail that surprises candidates coming from other trades with mandatory CE hours.
If you intend to hold "insured-to-contract" status, Maryland requires at least $300,000 in general liability coverage and $100,000 in property-damage coverage per occurrence. Confirm this coverage is in place before you plan to independently contract jobs.
Renewal fees match the initial license fee of $87.50 under the schedule effective July 1, 2025. For the complete financial picture across initial licensing, renewal, and insurance, see MD-MP Certification Cost 2026: Complete Pricing Breakdown.
Scheduling Your Prep Around the Domain Weights
Generic study techniques - timed review blocks, spaced repetition of flashcards, self-explanation of code sections - work well for MD-MP, but only when applied against the actual domain weighting, not spread evenly across all 10 areas.
Gas Appliances and Piping (Domain 9)
- Work through IFGC sizing and venting problems daily
- Tab your gas code sections first, since this domain alone is 40% of the exam
Drain, Waste, and Vent Systems (Domain 7) and Backflow Prevention (Domain 6)
- Review venting configurations and backflow device categories together, since both interact with water supply design
Water Supply Systems (Domain 5), Plumbing Mathematics (Domain 10), and remaining smaller domains
- Practice sizing calculations under timed conditions
- Do a final pass through Materials, Traps/Interceptors, Fixtures, Fundamentals, and Special Topics
This isn't a one-size-fits-all study calendar - it's built specifically around MD-MP's lopsided domain weights, where one domain outweighs six others combined. For a more detailed week-by-week plan, see MD-MP Study Guide 2026: How to Pass on Your First Attempt. You can also run realistic practice questions across all 10 domains at our MD-MP practice test platform to gauge where your weak spots actually are before test day.
Key Takeaway
Don't split study time evenly across 10 domains. Domain 9 alone equals the combined weight of six smaller domains - prioritize accordingly.
Who Hires Master Plumbers and Why the Credential Matters
Holding an MD-MP license opens doors to supervisory roles, independent contracting (with proper insurance), and gas fitting work that journey-level licensees cannot legally perform unsupervised. Employers across residential, commercial, and municipal plumbing contractors in Maryland look for the Master Plumber/Gas Fitter credential specifically when hiring for lead technician and supervisory positions. If you're evaluating whether the investment in exam fees, licensing, and prep time pays off for your career stage, Is the MD-MP Certification Worth It? Complete ROI Analysis 2026 lays out the considerations, and MD-MP Salary Guide 2026: Complete Earnings Analysis covers earnings potential. For active listings and role types, see MD-MP Jobs.
Candidates new to the terminology sometimes start with basic definitional questions before diving into exam mechanics. If that's you, our companion pieces - What Is MD-MP?, MD-MP Meaning, and What Does MD-MP Stand For? - cover the fundamentals before you commit to a study plan. You can start practicing right away at the main MD-MP practice test site regardless of where you are in the process.
Frequently Asked Questions
The MD-MP exam has 100 scored multiple-choice questions to complete within 240 minutes. PSI may add five to 10 unscored experimental questions, but the time spent on those doesn't count against your four-hour allowance for scored content.
You need 70% to pass. Full guidance on how that translates to missed questions per domain is available in MD-MP Passing Score 2026: Exactly What You Need to Pass.
Gas Appliances and Piping (Domain 9), which carries 40 of the 100 scored questions - by far the largest single domain on the exam.
No. Retesting is allowed no more often than every 30 days, so it's worth preparing thoroughly rather than planning on a quick retry.
No. General plumbing-license renewal in Maryland has no continuing education requirement. Licenses run two years from issuance, and renewal costs $87.50 under the fee schedule effective July 1, 2025.