- The MI-MP exam covers 11 domains across 130 questions in 180 minutes, with a 75% minimum passing score.
- PSI's bulletin (effective April 29, 2026) makes the 2021 Plumbing Code Book the exam reference - bring a bound copy with chapter tabs only.
- One computer-administered section is a drawing-based material takeoff covering back-to-back restrooms, fitting quantities, and drain/vent sizing.
- Domain 11 tests the Skilled Trades Regulation Act, 2016 PA 407, which is supplied onscreen - you don't need to memorize the statute cold.
MI-MP Exam Format Overview
The Michigan Master Plumber License Exam is administered by PSI Services LLC on behalf of the Michigan Department of Licensing and Regulatory Affairs (LARA), Bureau of Construction Codes. Candidates answer 130 questions in 180 minutes and need a minimum score of 75% to pass. Unlike a purely knowledge-recall test, the exam blends multiple-choice code and theory questions with a computer-administered drawing-based material takeoff, meaning some domains are tested through applied calculation rather than simple recall.
Understanding exactly how the 11 domains are organized - and which ones lean heavily on the 2021 Plumbing Code Book versus onscreen statutory references - is the foundation of an efficient prep plan. For a broader walkthrough of preparation strategy, see the MI-MP Study Guide 2026, and for the exact score mechanics behind that 75% threshold, check the MI-MP Passing Score guide.
All 11 MI-MP Exam Domains
PSI's official candidate bulletin lists eleven content areas for the Michigan Master Plumber License Exam. Below is what each one actually demands from a working journey plumber preparing for the master-level test.
Domain 1: Drainage Systems
Covers sizing and layout of building drains, sanitary sewers, and drainage piping under the 2021 Plumbing Code. Expect questions on pipe sizing tables, slope requirements, cleanout placement, and material compatibility.
- Drain sizing based on fixture unit loads
- Cleanout spacing and access requirements
Domain 2: General Knowledge
A broad category covering plumbing definitions, code administration, permit and inspection basics, and foundational terminology used throughout the code book. This domain rewards familiarity with how the code is organized as much as specific numbers.
- Code chapter organization and cross-references
- Definitions that affect how later questions are interpreted
Domain 3: Fixtures
Focuses on required fixture clearances, minimum fixture counts for occupancy types, fixture connections, and installation standards. Master-level questions often combine fixture requirements with drainage or venting scenarios.
- Minimum fixture requirements by occupancy
- Clearance and accessibility dimensions
Domain 4: Water Distribution
Tests sizing of water supply piping, pressure requirements, and material selection for potable water systems. Expect scenario-based questions requiring you to work through supply demand and pipe sizing charts.
- Water supply fixture unit calculations
- Pipe material and pressure-loss considerations
Domain 5: Backflow Protection
Covers cross-connection control, backflow preventer selection, and where different devices are required based on hazard level. This domain is a common weak spot for candidates who haven't recently installed backflow assemblies in the field.
- Device selection by hazard classification
- Installation clearance and testing access requirements
Domain 6: Storm Drains
Addresses roof drainage, storm sewer sizing, and separation from sanitary systems. Questions typically require applying rainfall-based sizing tables from the code book.
- Roof drain and leader sizing
- Secondary (overflow) drainage requirements
Domain 7: Special Waste
Covers handling of chemical, corrosive, or otherwise non-sanitary waste streams that require special piping materials or neutralization before entering the sanitary system.
- Acceptable materials for special waste piping
- Neutralization and dilution requirements
Domain 8: Testing
Focuses on required tests for drainage, water, and gas piping systems - pressures, durations, and acceptable methods before a system can be approved.
- Test pressures and hold times by system type
- Acceptable testing media
Domain 9: Inspections
Covers the inspection process itself: what must be visible or accessible at each inspection stage, and what triggers a failed inspection under Michigan's adopted code.
- Rough-in vs. final inspection requirements
- Documentation and access expectations
Domain 10: Venting
One of the most calculation-heavy domains, covering vent sizing, distance limitations, and acceptable venting methods - including concepts tested directly in the material takeoff exercise.
- Vent sizing relative to drain size
- Maximum trap-to-vent distances
Domain 11: Knowledge of the Skilled Trades Regulation Act, 2016 PA 407
Tests understanding of the statute governing skilled trades licensure in Michigan. The Act is supplied onscreen during the exam alongside the State Construction Code Act, 1972 PA 230, so this domain is more about applying provisions than memorizing statutory text.
- Licensure structure and enforcement provisions
- How the Act interacts with Bureau of Construction Codes authority
Key Takeaway
Because Domain 11 references are provided onscreen, spend your memorization energy on Domains 1, 4, 6, and 10 - the numerically heavy domains where you'll be doing sizing calculations under time pressure rather than reading provided text.
The Drawing-Based Material Takeoff
A distinctive feature of the Michigan Master Plumber License Exam is its computer-administered material takeoff component. Rather than answering isolated multiple-choice questions, candidates work from a drawing - commonly involving back-to-back restrooms - and must determine fitting quantities, drain and vent sizing, and appropriate venting methods based on what the drawing shows.
This section effectively blends Domains 1, 3, and 10 into a single applied exercise. You're not just recalling a sizing table; you're reading a layout, identifying fixture groupings, and working out the correct pipe and fitting counts the way you would on an actual job set of plans.
- Practice reading back-to-back restroom layouts and identifying shared drain/vent runs
- Rehearse counting fittings (elbows, tees, wyes) directly from a plan view
- Cross-check vent sizing decisions against drain sizing on the same drawing
Because this component rewards familiarity with plan-reading under time pressure, it's worth running through simulated takeoff exercises well before exam day rather than relying solely on textual review. The MI-MP Cheat Sheet condenses the sizing tables most relevant to this exercise into a single-page reference for quick drills.
Registration, Eligibility & Fees
Before you can sit for any of the 11 domains, LARA requires that you meet specific eligibility criteria and receive approval to test:
- At least 18 years old
- 4,000 hours working as a journey plumber, accumulated over at least the two years immediately preceding your application
- No lapse in journey licensure during that qualifying period
- LARA approval before PSI will schedule your exam
Once approved, PSI charges $100 per attempt, and that fee applies to retakes as well - so a candidate who fails on a weak domain pays the full fee again to retest. Testing is available at PSI test centers or via remote proctoring, with remote master-level testing having begun February 11, 2026. For the complete eligibility breakdown, see MI-MP Requirements 2026, and for a full cost picture including renewal fees, see MI-MP Certification Cost 2026.
It's worth remembering that the Master Plumber License is distinct from the plumbing contractor license - passing all 11 domains qualifies you at the master trade level, not automatically as a licensed contractor. Once licensed, renewal occurs every three years by April 30, with a $300 renewal fee, and code-update training is required within one year after Michigan adopts a new plumbing code.
| Exam Element | Detail |
|---|---|
| Total questions | 130 |
| Time allowed | 180 minutes |
| Passing score | 75% |
| PSI fee per attempt | $100 (retakes included) |
| Code reference | 2021 Plumbing Code Book (bound, tabbed only) |
| Delivery options | Test center or remote proctored |
Mapping a Study Schedule to the Domains
Rather than studying the 11 domains in the order PSI lists them, it makes sense to schedule the calculation-heavy domains earlier, when you have more mental bandwidth, and the reference-supported domains later, closer to exam day, since they require less rote memorization.
Drainage, Venting & Water Distribution
- Drill pipe and vent sizing tables from the 2021 code book
- Practice back-to-back restroom takeoff scenarios
Fixtures, Storm Drains & Special Waste
- Review fixture count requirements by occupancy
- Work through roof drain and storm sewer sizing problems
Backflow Protection, Testing & Inspections
- Match backflow device types to hazard classifications
- Memorize test pressures and hold times by system
General Knowledge, PA 407 & Final Review
- Skim the Skilled Trades Regulation Act sections available onscreen
- Run full-length timed practice covering all 11 domains
This sequencing works because the domains tested most heavily through calculation and the material takeoff (Domains 1, 4, 6, and 10) benefit from repetition spread across weeks, while Domain 11's onscreen statutory references mean it needs recognition, not memorization. For a deeper look at how difficult candidates typically find each domain in practice, see How Hard Is the MI-MP Exam?
Exam-Day Rules for References and Tools
The MI-MP exam is open book, but the rules around what "open book" means are strict and domain-agnostic - they apply across all 11 content areas:
- You may bring a bound 2021 Plumbing Code Book with chapter tabs only - no loose papers, sticky notes, highlighting, underlining, or indexing added during the exam
- The State Construction Code Act, 1972 PA 230, and the Skilled Trades Regulation Act, 2016 PA 407 (Domain 11) are supplied onscreen; personal paper copies of these are prohibited
- Personal calculators must be stored outside the examination room under PSI test-center security rules; you'll use whatever calculator PSI provides
Because you can't annotate your code book during the exam itself, any tabbing or organization needs to happen beforehand, based on how you expect to navigate between domains like drainage, venting, and water distribution under time constraints. Building this navigation skill is part of what separates confident first-attempt passes from candidates who burn time flipping pages. For more on how these testing conditions affect overall pass outcomes, see MI-MP Pass Rate 2026, and for scheduling logistics around test centers and remote proctoring windows, see MI-MP Exam Dates 2026.
Key Takeaway
Tab your code book by domain before exam day - since you cannot add tabs or notes during the test itself, your organization scheme has to be finalized in advance and tested against practice questions from every one of the 11 domains.
Once licensed, many master plumbers use the credential to qualify for supervisory roles, pull permits independently, or move into positions listed under MI-MP Jobs. If you're still weighing whether the time and fee investment make sense relative to career upside, Is the MI-MP Certification Worth It? walks through that decision, and the MI-MP Salary Guide 2026 looks at earnings considerations for licensed master plumbers. You can also start practicing domain-specific questions right now on our MI-MP practice test platform.
Frequently Asked Questions
The drawing-based material takeoff primarily draws on drainage systems, fixtures, and venting concepts, since it centers on back-to-back restroom layouts, fitting quantities, and drain/vent sizing.
The Skilled Trades Regulation Act, 2016 PA 407, along with the State Construction Code Act, 1972 PA 230, is supplied onscreen during the exam, so you need working familiarity rather than word-for-word memorization.
No. Only a bound 2021 Plumbing Code Book with chapter tabs is permitted, and you cannot add highlighting, underlining, indexing, or loose papers during the exam.
PSI's bulletin lists all 11 domains as the official content areas but does not publish a public per-domain question breakdown, so candidates should prepare thoroughly across every domain rather than assuming any one is minor.
You would need to retake the full exam and pay the $100 PSI fee again, since the Michigan Master Plumber License Exam is scored as a whole rather than by individual domain retake.