- PSI's CT-P2 bulletin organizes 70 scored questions across 16 named content areas, with 10 unscored items mixed in.
- Drain, Waste, and Vent is the single largest domain at 11 questions on the 150-minute exam.
- Isometric Analysis and Developed length together make up nine questions, so pipe-sizing math is unavoidable.
- A 70% score (49 of 70 scored questions) is required, and the exam is open-book with approved code references.
How the 16 Domains Fit Into the PSI Exam Blueprint
The Connecticut P-2 Unlimited Journeyperson Plumber exam is built and delivered by PSI Services LLC under contract with the Connecticut Department of Consumer Protection and the Plumbing and Piping Work Examining Board. Unlike a generic trade quiz, the CT-P2 test follows a published content outline that organizes every scored item into one of 16 defined domains. Candidates see 70 scored questions in 150 minutes, plus up to 10 additional unscored questions mixed in without identification - meaning every item on screen deserves full attention.
Because the exam is computer-based and open-book, the domains aren't just abstract categories - they map directly to the code books and reference manuals you're permitted to bring into the testing center. Understanding which domain a question belongs to helps you know which reference to flip to, and how fast you need to move to finish within the time limit.
Domain-by-Domain Breakdown
Below is what each of the 16 named content areas actually tests, based on the scope of practice for a P-2 Unlimited Journeyperson working under a licensed contractor in Connecticut.
Domain 1: General Plumbing Regulations
Covers Connecticut licensing structure, scope of work for a P-2 journeyperson, and how state statute interacts with adopted code editions.
- Know that P-2 holders may only work as employees of properly licensed contractors, not as independent operators.
Domain 2: Gas Systems
Fuel gas piping sizing, venting, appliance connections, and LP-gas specific rules drawn from NFPA 54 and NFPA 58.
- Distinguish natural gas requirements (NFPA 54) from LP-gas requirements (NFPA 58 2014 edition).
Domain 3: Cleanouts
Placement, sizing, and access requirements for cleanouts along drainage piping runs as required by the adopted plumbing code.
Domain 4: Fixtures and Equipment
Fixture unit values, minimum fixture requirements, and installation clearances for common residential and commercial fixtures.
Domain 5: Water Heaters
Sizing, venting, relief valve requirements, and installation clearances for water heating equipment.
Domain 6: Piping, Valves, Controls
Material selection, valve types, and control device placement across supply and distribution systems.
Domain 7: Water Supply
Sizing water distribution piping, pressure requirements, and demand calculations for supply systems.
Domain 8: Hangers and Supports
Spacing intervals and support methods for various pipe materials, both horizontal and vertical runs.
Domain 9: Drain, Waste, and Vent
The largest single domain on the CT-P2 exam at 11 scored questions. Covers DWV sizing, slope, venting methods, and fixture unit loading.
- Because this is the heaviest-weighted domain, allocate proportionally more review time here than any other single area.
Domain 10: Backflow
Cross-connection control, backflow preventer types, and where each device is required by code.
Domain 11: Traps and Interceptors
Trap seal requirements, venting relationships, and interceptor sizing for grease and other waste streams.
Domain 12: Developed length
Calculating actual pipe run length including fittings, used for venting and drainage sizing decisions. Combined with Isometric Analysis, this accounts for nine scored questions.
Domain 13: Isometric Analysis
Reading and interpreting isometric drawings to identify piping layout, fixture connections, and venting paths.
- Practice reading isometric drawings under time pressure - this pairs directly with Developed length questions.
Domain 14: Joints and Connections
Approved joining methods for various pipe materials, including solvent-welded, threaded, soldered, and mechanical connections.
Domain 15: Safety and Excavation
Trenching, shoring, and general jobsite safety principles, drawn largely from OSHA 29 CFR 1926.
Domain 16: Water Treatment
Water conditioning and processing systems for residential, commercial, and light industrial applications.
For a deeper walkthrough of how to sequence your review across all 16 areas, see the CT-P2 Study Guide 2026: How to Pass on Your First Attempt.
Which Domains Carry the Most Weight
PSI does not publish an exact question count for every one of the 16 domains, but two data points from the bulletin stand out clearly and should shape your priorities.
| Domain | Known Weight | Study Priority |
|---|---|---|
| Drain, Waste, and Vent | 11 scored questions | Highest - largest single domain |
| Isometric Analysis + Developed length (combined) | 9 scored questions | High - math and drawing interpretation |
| Remaining 13 domains | Split across remaining scored questions | Moderate - build steady coverage |
Key Takeaway
Drain, Waste, and Vent alone accounts for roughly one in seven of your scored questions. Treat it as the anchor domain of your entire study plan, not just one topic among sixteen.
If you're still gauging how challenging this exam is relative to your current trade knowledge, the breakdown in How Hard Is the CT-P2 Exam? Complete Difficulty Guide 2026 walks through where most candidates lose points across these domains.
Open-Book Reality: How References Map to Domains
One of the most distinctive features of the CT-P2 exam is that it's open-book. You bring your own approved references into the testing center, and PSI allows prior highlighting, underlining, annotation, and permanent tabs - but not question-and-answer notes, loose papers, temporary tabs, or writing during the exam itself. A silent, nonprinting, nonprogrammable calculator is also permitted.
Knowing which domain draws from which book lets you tab your references strategically before test day:
- Domains 3, 4, 6, 7, 9, 11, 14: International Plumbing Code (2015, 2018, or 2021 edition, your choice)
- Domain 2 (natural gas): NFPA 54 National Fuel Gas Code or Handbook, 2012
- Domain 2 (LP-gas): NFPA 58 Liquefied Petroleum Gas Code, 2014
- Domain 15: OSHA 29 CFR 1926 with latest amendments or PSI-listed selections
- Domain 16: Water Processing: Residential, Commercial, Light Industrial, third edition, 2000, and NFPA 56
Two additional titles - Mathematics for Plumbers and Pipefitters and Plumbing Design and Installation - are useful for building skills in Domains 12 and 13, but they are study-only resources and cannot be brought into the exam room.
Building a Domain-Focused Study Schedule
A generic study calendar won't respect how unevenly weighted these 16 domains actually are. Instead, sequence your weeks around the exam's real point distribution.
Drain, Waste, and Vent + Traps and Interceptors
- Work sizing problems from the IPC edition you'll bring to the exam
- Drill fixture unit tables until recall is automatic
Isometric Analysis + Developed length
- Practice reading isometric drawings against a timer
- Use Mathematics for Plumbers and Pipefitters for sizing calculations
Gas Systems, Water Supply, Backflow, Water Heaters
- Cross-reference NFPA 54, NFPA 58, and IPC water supply chapters
- Tab your code books for these sections now
Remaining domains + full timed practice
- Cover General Plumbing Regulations, Cleanouts, Fixtures, Hangers, Piping/Valves, Joints, Safety, Water Treatment
- Run full-length timed sets to build 150-minute pacing
This sequencing isn't a rigid template - adjust it based on which domains feel weakest for you personally. What matters is that the heaviest-weighted domains get the earliest and most repeated exposure, not equal time with the lightest ones.
Who Uses These Domains on the Job
Every one of these 16 domains reflects real field work a P-2 Unlimited Journeyperson performs daily while employed by a licensed plumbing contractor. DWV and Traps and Interceptors show up on nearly every residential and commercial rough-in. Gas Systems and Water Heaters come into play on service calls and new installs alike. Isometric Analysis is exactly what a journeyperson reads off a set of plans before running pipe, and Safety and Excavation reflects OSHA obligations on any trench or utility work.
Because P-2 is an employee-only license - holders cannot contract independently - the domains are scoped to the knowledge a working journeyperson needs under supervision of a licensed contractor, not the business and legal knowledge required of a P-1 contractor license. If you're weighing what this credential unlocks in terms of employment and pay, see CT-P2 Salary Guide 2026: Complete Earnings Analysis and CT-P2 Jobs for more on where this license is used.
For candidates still confirming eligibility before scheduling with PSI - including the DCP equivalency pathway of 8,000 on-the-job hours and 576 classroom hours - review CT-P2 Requirements 2026: Eligibility, Prerequisites & How to Qualify before you commit to a study timeline built around these domains.
You can also practice questions organized by these exact 16 domains at CT-P2 Exam Prep, and track your readiness domain-by-domain before scheduling your official PSI appointment through the main practice test platform.
Frequently Asked Questions
PSI publishes exact counts for only two areas: Drain, Waste, and Vent (11 questions) and the combined Isometric Analysis plus Developed length pairing (9 questions). The remaining 50 scored questions are distributed across the other 13 domains without a published per-domain breakdown.
Yes. All 70 scored questions plus any unscored items are open-book, drawing from your approved IPC edition, NFPA 54, NFPA 58, OSHA 29 CFR 1926, Water Processing third edition, and NFPA 56 - depending on which domain the question falls under.
You need to know where to find information fast, not memorize it word-for-word. With 150 minutes covering up to 80 total questions, candidates who haven't practiced navigating their references under time pressure often run short on time.
You need 70% overall, equal to 49 of the 70 scored questions correct. There's no requirement to pass each domain individually - it's one combined score. See CT-P2 Passing Score 2026: Exactly What You Need to Pass for more detail.
Your DCP-approved eligibility lasts one year with unlimited exam attempts during that period, so you can retake the $59 PSI exam and focus your review on the domain that cost you points. Check CT-P2 Certification Cost 2026: Complete Pricing Breakdown for full fee details before scheduling a retake.