- IN-JP Domain Breakdown at a Glance
- Domain 1: Developed Length/Isometric Analysis
- Domain 2: Fixtures
- Domain 3: General Requirements
- Domain 4: Indiana Business
- Domain 5: Sanitary Drainage
- Domain 6: Storm Water Systems
- Domain 7: Vents
- Domain 8: Water Heaters
- Domain 9: Water Supply and Distribution
- What You Can Bring Open-Book
- Sequencing Your Prep Around the Weight
- FAQ
- The IN-JP exam has 90 questions across 9 domains, with Vents weighted heaviest at 17 questions.
- Sanitary Drainage (15) and Water Supply and Distribution (14) are the next two largest domains.
- Indiana Business contributes only 6 questions but covers licensing rules unique to Indiana.
- The June 24, 2026 Prov bulletin governs which code editions and amendments you can bring open-book.
IN-JP Domain Breakdown at a Glance
The Indiana Journeyman Plumber License Exam (IN-JP), administered through the Indiana Plumbing Commission and the Indiana Professional Licensing Agency with Prov, Inc. delivering the test, is built from 90 multiple-choice questions spread across nine content areas. Unlike exams that weight every topic evenly, IN-JP concentrates roughly a third of its questions in just two domains - Vents and Sanitary Drainage - while treating others like Storm Water Systems and Indiana Business as smaller but still scoreable sections.
Knowing exactly how many questions come from each domain lets you allocate study hours proportionally instead of guessing. Below is the official question allocation in domain order.
| Domain | Questions | Share of 90 |
|---|---|---|
| 1. Developed Length/Isometric Analysis | 8 | ~9% |
| 2. Fixtures | 10 | ~11% |
| 3. General Requirements | 7 | ~8% |
| 4. Indiana Business | 6 | ~7% |
| 5. Sanitary Drainage | 15 | ~17% |
| 6. Storm Water Systems | 6 | ~7% |
| 7. Vents | 17 | ~19% |
| 8. Water Heaters | 7 | ~8% |
| 9. Water Supply and Distribution | 14 | ~16% |
If you haven't yet reviewed the mechanics of the test itself - timing, delivery format, and attempt limits - the IN-JP Study Guide 2026: How to Pass on Your First Attempt walks through the full test-day picture before you dive into domain content.
Domain 1: Developed Length/Isometric Analysis
What This Domain Covers
This is the drawing-interpretation domain. Expect isometric piping diagrams where you must calculate developed length, identify fitting allowances, and trace a system from fixture to stack. With 8 of 90 questions, it's a moderate slice, but it's also one of the few domains that tests spatial reasoning rather than pure code lookup.
- Reading isometric drawings and converting them to actual pipe runs
- Accounting for fitting take-offs when calculating total developed length
- Identifying missing or incorrectly sized segments on a diagram
Because these questions require you to work through a diagram rather than recall a single code section, practicing with sample isometrics before test day is more valuable here than in code-lookup-heavy domains.
Domain 2: Fixtures
What This Domain Covers
At 10 questions, Fixtures covers the installation, spacing, and connection requirements for the plumbing fixtures a journeyman installs day to day - sinks, water closets, tubs, showers, and similar equipment.
- Minimum clearances and spacing between fixtures
- Trap and vent connection requirements at the fixture
- Fixture unit values used elsewhere in drainage and supply calculations
Fixture unit values you learn here carry directly into Domain 5 (Sanitary Drainage) and Domain 9 (Water Supply and Distribution) calculations, so treat this domain as foundational rather than standalone.
Domain 3: General Requirements
What This Domain Covers
General Requirements (7 questions) is the administrative and code-application layer - permit-related provisions, inspection expectations, and the baseline definitions that the rest of the exam assumes you already know.
- Scope and applicability sections of the adopted code
- Definitions that recur across other domains
- Materials and workmanship standards
This domain rewards familiarity with how the code book is organized more than memorization of a single fact - knowing where to look matters as much as knowing the answer.
Domain 4: Indiana Business
What This Domain Covers
Indiana Business contributes 6 questions within this examination and is the one domain that is entirely Indiana-specific rather than derived from the national plumbing code. It reflects licensing structure, scope of practice, and regulatory administration under the Indiana Plumbing Commission.
- Licensing categories and the Commission's oversight role
- Scope-of-work boundaries for a journeyman versus a contractor license
- Administrative rules referenced in 860 IAC provisions
Because this domain is small, some candidates under-study it - but skipping it outright risks leaving easy points on the table. For a deeper look at how eligibility and licensing rules intersect with this domain, see IN-JP Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Domain 5: Sanitary Drainage
What This Domain Covers
Sanitary Drainage is the second-largest domain at 15 questions. It covers the design and sizing of drain, waste, and stack systems that carry sewage and wastewater away from fixtures.
- Drainage fixture unit (DFU) sizing for horizontal and vertical piping
- Slope, cleanout placement, and offset requirements
- Building drain and building sewer sizing criteria
Key Takeaway
Sanitary Drainage and Vents are conceptually linked - every drainage system you size also needs a vent path. Study them back-to-back rather than as isolated topics.
Domain 6: Storm Water Systems
What This Domain Covers
Storm Water Systems is tied with Indiana Business for the smallest domain at 6 questions, focused on roof drainage, gutters, leaders, and storm sewer sizing rather than sanitary waste.
- Roof drain and secondary (overflow) drain requirements
- Leader and conductor sizing based on roof area and rainfall rate
- Combined versus separate storm and sanitary systems
Because it's a small domain, a focused review session rather than a multi-week study block is usually sufficient once the larger domains are solid.
Domain 7: Vents
What This Domain Covers
Vents is the single largest domain on IN-JP at 17 of 90 questions - nearly one in five questions on the exam. It covers how drainage systems are protected from siphonage and back-pressure through proper venting.
- Individual, common, wet, circuit, and combination venting configurations
- Vent sizing based on drainage fixture units and developed length
- Vent termination location and height requirements
Domain 8: Water Heaters
What This Domain Covers
Water Heaters carries 7 questions and covers installation, venting, and safety-device requirements for water heating equipment installed by a journeyman plumber.
- Temperature and pressure relief valve requirements and discharge piping
- Combustion air and venting for fuel-fired water heaters
- Seismic strapping and clearance requirements
Domain 9: Water Supply and Distribution
What This Domain Covers
Water Supply and Distribution is the third-largest domain at 14 questions, covering how potable water is sized, distributed, and protected from contamination throughout a building.
- Water supply fixture unit (WSFU) sizing methods
- Backflow prevention device selection and placement
- Pipe material, sizing, and pressure requirements for distribution systems
Together, Vents, Sanitary Drainage, and Water Supply and Distribution account for 46 of the 90 questions - over half the exam. Any realistic prep plan has to put these three domains at the center, a point covered in more depth in How Hard Is the IN-JP Exam? Complete Difficulty Guide 2026.
What You Can Bring Open-Book
IN-JP is an open-book exam, but the allowed materials are tightly defined by the June 24, 2026 Prov candidate information bulletin. Getting this wrong doesn't just cost you points - it can get materials confiscated at check-in.
- Code editions allowed: the 2006 IPC, second printing, Indiana 2012 edition, or the listed 2006 substitutions, plus the 2012 Indiana Amendments and the 2014 Indiana legal compilation or Indiana Plumbing Supplement
- Reference list: use the journeyman reference list specifically - not the plumbing-contractor list, which allows different materials
- Tabs and notes: permanent tabs and highlighting are allowed; handwritten formulas in ink are the specific notes exception
- Printouts: authorized printouts of listed amendments and statutes are allowed
- Not allowed: movable tabs, copied books, and practice-question materials
- Calculators: simple four-function calculators are permitted at test centers; remote Examroom testing has its own separate equipment and workspace rules
Key Takeaway
Tab your journeyman reference books by domain - especially Vents, Sanitary Drainage, and Water Supply and Distribution sections - before test day, since permanent tabs are allowed but must be placed in advance, not improvised mid-exam.
Sequencing Your Prep Around the Weight
Because domain weight is so uneven on IN-JP, a generic week-by-week template doesn't serve candidates well. Instead, sequence study blocks by question count, starting with the domains that can move your score the most.
Vents and Sanitary Drainage (32 questions combined)
- Work through venting configurations alongside DFU sizing tables
- Practice isometric-style problems that combine drainage and venting
Water Supply and Distribution and Fixtures (24 questions combined)
- Drill WSFU sizing and backflow device placement
- Connect fixture unit values back to Domain 5 and Domain 9 calculations
Developed Length/Isometric Analysis, General Requirements, Water Heaters
- Practice reading and calculating from isometric drawings
- Review relief valve, venting, and clearance rules for water heaters
Storm Water Systems, Indiana Business, and full open-book drills
- Confirm your reference book tabs match the journeyman reference list
- Run timed practice using only your permitted code editions and notes
Adjust the timeline to how much runway you have before your test date - see IN-JP Exam Dates 2026: Testing Windows, Deadlines & Scheduling for scheduling mechanics, including the three-business-day reschedule rule and the requirement that your first attempt occur within one year of Commission approval.
Once you've mapped out domain weight and reference materials, it helps to see how these details connect to the bigger picture of what a passing score actually requires - covered in IN-JP Passing Score 2026: Exactly What You Need to Pass - and how the overall cost of licensure breaks down in IN-JP Certification Cost 2026: Complete Pricing Breakdown. If you're still weighing whether pursuing the license makes sense for your career, Is the IN-JP Certification Worth It? Complete ROI Analysis 2026 and IN-JP Salary Guide 2026: Complete Earnings Analysis put the domain content in context against the broader payoff. For hands-on practice organized by these exact nine domains, the question sets on the main practice test platform mirror the official allocation so you spend more time on Vents and Sanitary Drainage and less on lower-weight areas.
Frequently Asked Questions
Vents is the largest domain with 17 of 90 questions, followed by Sanitary Drainage at 15 and Water Supply and Distribution at 14.
Yes. Six questions is still nearly seven percent of the exam, and the content - licensing scope and Commission administration - is distinct from anything covered in the code-based domains, so it can't be picked up by osmosis while studying the others.
No. IN-JP candidates must use the journeyman reference list specifically, not the plumbing-contractor list, since the two lists permit different materials.
You still need to know where each table lives and how to apply it quickly, since 180 minutes for 90 questions leaves limited time to search an unfamiliar reference during domains like Sanitary Drainage and Water Supply and Distribution.
Yes, the content domains and question allocation are identical; only the equipment and workspace rules differ between in-person test centers and remote Examroom delivery.