- How the 100-Question Blueprint Is Built
- Domain 1: Plumbing Fundamentals and Safety
- Domain 2: Materials, Uses, and Specifications
- Domain 3: Traps, Interceptors, and Backwater Valves
- Domain 4: Plumbing Fixtures, Fixture Fittings, and Plumbing Appliances
- Domain 5: Water Supply Systems
- Domain 6: Backflow Prevention
- Domain 7: Drain, Waste, and Vent Systems
- Domain 8: Gas Appliances and Piping
- Domain 9: Plumbing Mathematics
- Scheduling Your Review Around the Two Heaviest Domains
- Who Sits for This Exam and Why the Domains Matter
- Frequently Asked Questions
- The Maryland Journey Plumber/Gas Fitter exam covers 100 scored questions across 9 domains in 240 minutes.
- Gas Appliances and Piping carries the largest allocation, followed by Drain, Waste, and Vent Systems and Backflow Prevention.
- PSI may add 5-10 unscored experimental questions with extra time outside the 240-minute base allowance.
- You need 70% to pass, per the PSI candidate bulletin and COMAR 09.20.02.03.
How the 100-Question Blueprint Is Built
The Maryland State Board of Plumbing, under the Maryland Department of Labor, defines nine content domains for the combined Journey Plumber/Gas Fitter examination administered by PSI Services LLC. Every version of the base exam draws from these same nine areas to produce 100 scored multiple-choice questions delivered in a 240-minute computer-based session. PSI may also insert five to ten additional unscored, experimental questions that are not counted toward your final score, and candidates are given extra time outside the 240-minute base allowance to accommodate them - so don't panic if your seat time looks slightly longer than expected.
Passing requires a 70% score, a figure confirmed both in the PSI candidate bulletin and in COMAR 09.20.02.03. If you want the full breakdown of how that number is calculated and why it matters more than raw question count, see MD-JP Passing Score 2026: Exactly What You Need to Pass.
Of the nine domains, Gas Appliances and Piping receives the largest share of questions, with Drain, Waste, and Vent Systems and Backflow Prevention close behind as the next-heaviest areas. That weighting alone should shape how you divide study time - a candidate who spends equal hours on all nine domains is almost certainly under-preparing for the sections that will decide the outcome.
Domain 1: Plumbing Fundamentals and Safety
Plumbing Fundamentals and Safety
This domain establishes the baseline knowledge every journeyman is expected to carry onto a jobsite: general safety practices, jobsite hazard recognition, and the foundational vocabulary used throughout the rest of the exam.
- Personal protective equipment and general jobsite hazard controls
- Basic terminology used across code references
- General responsibilities tied to licensed practice in Maryland
Questions here tend to read straightforward, but they set the tone for the open-book format - you're expected to know when to look something up versus when to answer from memory. For a broader look at how this domain fits into overall exam difficulty, see How Hard Is the MD-JP Exam? Complete Difficulty Guide 2026.
Domain 2: Materials, Uses, and Specifications
Materials, Uses, and Specifications
Covers pipe, fitting, and fixture materials, along with correct application by system type and location.
- Approved materials for water supply, drainage, and gas piping
- Compatibility and joining methods between dissimilar materials
- Specification limits tied to use, temperature, and pressure
Expect scenario questions that ask which material is permitted in a given application rather than pure definitions - this is where a well-tabbed reference book earns its keep during the exam.
Domain 3: Traps, Interceptors, and Backwater Valves
Traps, Interceptors, and Backwater Valves
Focuses on trap seal protection, grease and oil interceptor sizing and placement, and backwater valve installation to prevent sewage backflow into fixtures.
- Trap seal depth and siphonage prevention
- When interceptors are required and how they're sized
- Backwater valve placement relative to fixture elevation
Domain 4: Plumbing Fixtures, Fixture Fittings, and Plumbing Appliances
Plumbing Fixtures, Fixture Fittings, and Plumbing Appliances
Tests knowledge of fixture types, required fittings, and the appliances connected to them, including installation clearances and connection requirements.
- Fixture unit assignments and minimum clearances
- Required fittings and shutoff valve placement
- Appliance connections that intersect with water or drainage systems
Domain 5: Water Supply Systems
Water Supply Systems
Covers distribution piping design, sizing principles, water hammer control, and protection of potable water quality throughout the supply system.
- Pipe sizing logic based on fixture demand
- Water hammer arrestor placement and function
- Protection of the potable supply from contamination points
Because water supply questions often overlap with backflow concepts, candidates who study these two domains together tend to retain the material better than those who treat them as unrelated topics.
Domain 6: Backflow Prevention
Backflow Prevention
One of the two second-largest domains on the exam, this section tests assembly types, application, and testing principles tied directly to Maryland's licensing structure.
- Backflow assembly types and where each is required
- Cross-connection hazard identification
- Testing concepts tied to the 32-hour backflow-prevention device testing course required for eligibility
Key Takeaway
The 32-hour backflow-prevention device testing course isn't just an eligibility checkbox - it directly supports one of the exam's heaviest-weighted domains, so treat that coursework as exam prep, not a separate task.
Domain 7: Drain, Waste, and Vent Systems
Drain, Waste, and Vent Systems
The other second-largest domain, DWV questions test system design logic more than memorization - slope, venting method, and fixture unit loading all interact.
- Drainage pipe slope and sizing by fixture unit load
- Vent system types and when each is permitted
- Cleanout placement and access requirements
Because Drain, Waste, and Vent Systems and Backflow Prevention together make up a large share of the exam alongside Gas Appliances and Piping, mastering these three domains should be the backbone of any study plan. The MD-JP Study Guide 2026: How to Pass on Your First Attempt walks through how to sequence review across all nine areas.
Domain 8: Gas Appliances and Piping
Gas Appliances and Piping
As the largest domain on the combined Journey Plumber/Gas Fitter exam, this section reflects the "Gas Fitter" half of the license and deserves proportionally more study hours than any other area.
- Gas piping sizing and material selection
- Appliance venting and combustion air requirements
- Shutoff valve placement and pressure testing concepts
Because this domain is tied to the 2018 IFGC reference (pending confirmation of any 2024-code update), make sure your tabbed reference copy matches the edition PSI assigns for your scheduled test date.
Domain 9: Plumbing Mathematics
Plumbing Mathematics
Applies calculation skills across pipe sizing, slope, volume, and pressure conversions rather than testing formulas in isolation.
- Slope and grade calculations for drainage runs
- Volume and capacity conversions
- Pressure and elevation relationships
Remember that only a silent, nonprinting, nonprogrammable calculator without an alphabetic keyboard is permitted during the exam - verify your device meets this standard well before test day, since a disallowed calculator can cause delays at check-in.
Scheduling Your Review Around the Two Heaviest Domains
Generic weekly study templates don't hold up well against a nine-domain, unevenly weighted exam. Instead, build your schedule around the actual point distribution: start with Gas Appliances and Piping since it carries the most questions, move into Drain, Waste, and Vent Systems and Backflow Prevention next, and treat the remaining six domains as a second pass once the top three are solid.
Gas Appliances and Piping
- Review gas piping sizing tables and appliance venting rules
- Practice questions specific to combustion air and shutoff placement
Drain, Waste, and Vent Systems & Backflow Prevention
- Work through slope and venting scenario questions
- Cross-study backflow assembly types with water supply protection concepts
Remaining Six Domains
- Cover Materials, Fixtures, Traps, Water Supply, Fundamentals, and Mathematics
- Run full-length timed practice sets under open-book conditions
If you're unsure how much total time to allocate before your scheduled test date, cross-reference your plan against MD-JP Exam Dates 2026: Testing Windows, Deadlines & Scheduling so your review timeline lines up with your actual registration window.
Who Sits for This Exam and Why the Domains Matter
Candidates reach this exam after four years as a licensed apprentice and 7,500 hours working under a licensed Master, with up to 1,500 approved school hours allowed to count toward that experience total. A current, approved 32-hour backflow-prevention device testing course is also required before you're eligible to sit. If you haven't confirmed you meet every prerequisite, review MD-JP Requirements 2026: Eligibility, Prerequisites & How to Qualify before scheduling with PSI.
Registration itself runs through PSI's online-only application process (required since March 31, 2025), with a $65 examination fee. Passing candidates then have one year to apply for the license, and the initial license plus each biennial renewal costs $43.50 under the July 1, 2025 Board fee schedule - with no routine continuing education requirement for an ordinary Journey license. A full cost breakdown, including how these fees compare across the licensing lifecycle, is available in MD-JP Certification Cost 2026: Complete Pricing Breakdown.
It's worth noting that WSSC and Baltimore County maintain separate licensing arrangements outside the standard Board process, so candidates working primarily in those jurisdictions should verify which pathway applies to them before assuming the statewide domain structure covers every local requirement.
Passing this exam opens doors across residential, commercial, and gas-service contracting roles throughout Maryland. If you're weighing whether the license pays off relative to the time invested in these nine domains, Is the MD-JP Certification Worth It? Complete ROI Analysis 2026 and MD-JP Salary Guide 2026: Complete Earnings Analysis look at that question directly, while MD-JP Jobs covers where licensed journeymen typically find work.
| Domain | Relative Weight | Core Focus |
|---|---|---|
| Gas Appliances and Piping | Largest | Sizing, venting, combustion air, pressure testing |
| Drain, Waste, and Vent Systems | Second-largest | Slope, venting method, fixture unit loading |
| Backflow Prevention | Second-largest | Assembly types, cross-connection hazards |
| Remaining six domains | Smaller, combined | Fundamentals, materials, traps, fixtures, water supply, math |
Because the Board's reported outcomes are monthly cohort figures rather than annual or first-attempt statistics, don't try to reverse-engineer a difficulty score from a single month's numbers. For the full context behind the Board's most recent reported results, see MD-JP Pass Rate 2026: What the Data Shows. And if a retest is needed, remember candidates may retest once per 30 days.
For a condensed reference you can review the night before your test, the MD-JP Cheat Sheet 2026: One-Page Review of Must-Know Facts distills the domain weights and key numbers covered here. You can also start building domain-specific familiarity right now with timed practice questions on the main MD-JP practice test platform, which mirrors the same nine-domain structure used by PSI.
Frequently Asked Questions
The Board publishes relative allocations rather than a fixed count per domain for every form. Gas Appliances and Piping is the largest domain, with Drain, Waste, and Vent Systems and Backflow Prevention as the next-heaviest, while the remaining six domains fill out the rest of the 100 scored questions.
No. PSI may include five to ten unscored experimental questions mixed into the exam with additional time provided outside the 240-minute base allowance, but candidates cannot identify which questions are scored versus experimental.
The public PSI bulletin lists the 2018 IFGC, but June 2026 Board minutes discuss a 2024-code update. Confirm the exact edition assigned to your test date directly with PSI before purchasing or tabbing reference material.
The 32-hour approved backflow-prevention device testing course is an eligibility requirement, and its content directly supports the concepts tested in the Backflow Prevention domain, so treat it as genuine exam preparation.
Candidates may retest once per 30 days, and the domain structure and weighting remain the same across retest attempts since both draw from the same Board-defined blueprint.