- The Exact Passing Score: 84 of 120
- How the Five-Hour Clock and Unscored Questions Work
- Where the Points Live: Domain Weighting Breakdown
- Registration, Fees, and Scheduling Mechanics
- What You Can and Cannot Bring Into the Testing Room
- A Study Timeline Built Around the Score You Need
- What Happens If You Fall Short
- FAQ
- You need 84 correct answers out of 120 scored questions on the C-1 trade exam - exactly 70%.
- PSI may slip in 1-10 unscored experimental items that still count against your five-hour clock.
- Drain, Waste, and Vents carries the most weight at 10 items; four domains tie for second at 8 items each.
- The exam is open-book, but only five named references - UPC 2018, UMC 2018, NFPA 54 (2012), NFPA 58 (2014), and NFPA 13 (2019) - are permitted in the room.
The Exact Passing Score: 84 of 120
The Nevada Plumbing and Heating Contractor (C-1) Trade Exam is scored on a simple threshold: 120 scored questions, five-hour limit, 84 correct answers required to pass. That 84/120 works out to 70%, and it is a fixed number - there is no curve, no rounding in your favor, and no partial credit for questions you leave blank. Missing 37 questions still lets you pass; missing 37 caps you out with a single question to spare, which is why domain-by-domain preparation matters more than general familiarity with plumbing and heating trade practice.
It's worth being precise about which exam this passing standard applies to. This article covers the full C-1 Plumbing and Heating Contractor trade examination administered through PSI Services LLC on behalf of the Nevada State Contractors Board - not the narrower C-1d plumbing-only exam, and not the separate Contractor Management Survey (CMS) business-and-law exam, which uses its own 75% passing standard. If you're bundling both exams into one testing appointment, keep your CMS studying and your trade-exam studying in separate lanes; blending the two content sets is a common way candidates lose points on both.
How the Five-Hour Clock and Unscored Questions Work
The C-1 trade exam is computer-administered and open-book, and PSI may add between 1 and 10 unscored experimental questions to any given form. These experimental items look identical to scored questions - you won't know which ones count - and they still consume your five-hour testing window. Practically, that means your real pacing target isn't "120 questions in 300 minutes" but closer to "up to 130 questions in 300 minutes," so budgeting roughly two minutes per question, with slack for the harder isometric and mathematics problems, keeps you from running out of time on the back end.
Because the format is open-book, some candidates assume the exam is easier than a closed-book test. It isn't. Flipping through the UPC or UMC to locate a table or code section under time pressure can burn more minutes than simply knowing the material cold. The candidates who finish comfortably are the ones who've pre-tabbed their references and only open the books to confirm a number, not to learn a concept for the first time. For a deeper look at why the open-book format doesn't translate into an easy exam, see How Hard Is the NV-C1 Exam? Complete Difficulty Guide 2026.
Key Takeaway
Plan your pacing for roughly 125-130 questions, not exactly 120, since unscored experimental items are indistinguishable from scored ones and still eat exam time.
Where the Points Live: Domain Weighting Breakdown
The passing score is a single number, but it's built from 23 unevenly weighted domains. Based on the official PSI bulletin allocation, here's how the 120 scored questions break down by content area:
| Domain | Scored Items |
|---|---|
| Drain, Waste, and Vents | 10 |
| Gas Systems | 8 |
| Water Supply | 8 |
| Traps and Interceptors | 8 |
| Isometric Analysis/Plumbing Mathematics | 8 |
| General Plumbing Requirements | 7 |
| Water Heaters/Venting | 6 |
| Chilled Water Piping | 6 |
| Hangers and Supports | 5 |
| Safety | 5 |
| Fire Sprinklers | 5 |
| Storm Drainage | 5 |
| Boilers | 4 |
| Cleanouts | 4 |
| Fixtures and Equipment | 4 |
| Backflow | 4 |
| Joints and Connections | 4 |
| Solar | 4 |
| Hydronics | 3 |
| Piping, Valves, and Controls | 3 |
| Sheet Metal | 3 |
| Industrial Piping | 3 |
| Breathing Systems for Firefighters | 3 |
Four domains - Gas Systems, Water Supply, Traps and Interceptors, and Isometric Analysis/Plumbing Mathematics - sit right behind Drain, Waste, and Vents at 8 items apiece. Together with DWV, these five domains account for 42 of the 120 scored questions, more than a third of the entire exam. If you only have time to master a handful of domains cold, these are the five that move your score the most. For a full walkthrough of what each domain actually tests, cross-reference NV-C1 Exam Domains 2026: Complete Guide to All 23 Content Areas.
Drain, Waste, and Vents
The single largest domain at 10 items. Expect questions on sizing, slope, venting configurations, and code-based sizing tables from the UPC.
- Know how to read and apply UPC sizing tables without hesitation
- Practice vent stack and relief vent scenarios, not just definitions
Isometric Analysis/Plumbing Mathematics
Tied for second-largest at 8 items. This domain rewards candidates who can read an isometric drawing and run the math under time pressure, not just recognize terminology.
- Practice converting isometric layouts into pipe-sizing calculations
- Bring a silent, nonprinting, nonprogrammable calculator with no alphabetic keyboard
Registration, Fees, and Scheduling Mechanics
Passing the exam is only one gate. Before you can even schedule with PSI, the Nevada State Contractors Board has to approve your application, which includes verifying that you meet the experience requirement - ordinarily four full years of qualifying journeyman, supervisory, or contractor experience within the preceding 15 years, with Board-approved education able to substitute for up to three of those years. Financial, bond, and applicable insurance requirements are reviewed at this stage too. The NV-C1 Requirements 2026: Eligibility, Prerequisites & How to Qualify guide breaks down exactly how the Board evaluates that experience.
Once approved, exam-related costs are straightforward:
- PSI charges $95 to sit for one examination portion (the C-1 trade exam alone).
- PSI charges $140 if you pair the trade exam with the CMS business-and-law exam in the same sitting.
- The Board application fee is $300.
- An initial two-year license runs $600, and biennial renewal is also $600, alongside ongoing bond and applicable insurance compliance.
A full accounting of every dollar in this process - application, testing, licensing, and renewal - is laid out in NV-C1 Certification Cost 2026: Complete Pricing Breakdown. If you're mapping out when to schedule relative to Board approval timelines, NV-C1 Exam Dates 2026: Testing Windows, Deadlines & Scheduling covers the sequencing in more detail.
What You Can and Cannot Bring Into the Testing Room
Because this is an open-book exam, the rules around materials matter as much as the rules around content. Exactly five references are approved in the testing room:
- UPC 2018 (Uniform Plumbing Code)
- UMC 2018 (Uniform Mechanical Code)
- NFPA 54 (2012)
- NFPA 58 (2014)
- NFPA 13 (2019)
These are the only admitted books - other study references you may use during preparation are not permitted at the testing center, so don't confuse a study resource with an exam-room resource. Advance highlighting, underlining, and permanent tabs on the approved books are allowed, which means you should prepare your copies well before test day. Handwritten notes, loose papers, and temporary tabs are prohibited, so any sticky flag that isn't permanently affixed will likely be pulled before you sit down. A silent, nonprinting, nonprogrammable calculator without an alphabetic keyboard is also allowed, which matters directly for the Isometric Analysis/Plumbing Mathematics domain. If you're still assembling your reference set, Nevada C-1 exam books and study materials should be sourced and tabbed weeks in advance, not the night before.
Key Takeaway
Tab your five approved references permanently before test day - temporary tabs and loose notes get rejected at check-in, wasting time you need for the actual exam.
A Study Timeline Built Around the Score You Need
Generic study advice rarely accounts for the fact that Drain, Waste, and Vents is worth two and a half times as many points as Hydronics. A smarter approach allocates study weeks proportionally to domain weight, front-loading the five heaviest domains before spreading remaining time across the rest.
Heavy Domains, Round One
- Drain, Waste, and Vents (10 items) and Gas Systems (8 items)
- Build UPC and NFPA 54 tab systems as you go
Heavy Domains, Round Two
- Water Supply, Traps and Interceptors, and Isometric Analysis/Plumbing Mathematics (8 items each)
- Practice calculator-based problems under a timed clock
Mid-Weight Domains
- General Plumbing Requirements, Water Heaters/Venting, Chilled Water Piping
- Cross-reference UMC and NFPA 58 sections as they come up
Remaining Domains and Full Simulations
- Cover Boilers, Backflow, Safety, Fire Sprinklers, and the remaining lighter domains
- Run at least two full five-hour timed simulations with only the five approved references
A structured walkthrough of this kind of weighted plan, including which domains pair well for review sessions, is available in NV-C1 Study Guide 2026: How to Pass on Your First Attempt. For a quick-reference version once you're closer to test day, NV-C1 Cheat Sheet 2026: One-Page Review of Must-Know Facts condenses the highest-yield facts into a single page.
What Happens If You Fall Short
If you don't reach 84 correct answers, you're not locked out permanently, but the retake process has real friction built in. Failed attempts require a two-week wait before you can sit again, and three failures void the application entirely - meaning you'd need to restart the Board approval process from scratch, not just rebook a PSI appointment. That structure rewards candidates who treat their first attempt seriously rather than as a diagnostic run.
If you want a realistic sense of how candidates generally perform against this passing standard, NV-C1 Pass Rate 2026: What the Data Shows puts the scoring threshold in context. And if you're weighing whether the licensing investment is worthwhile relative to the work it opens up, Is the NV-C1 Certification Worth It? Complete ROI Analysis 2026 and NV-C1 Salary Guide 2026: Complete Earnings Analysis look at the license from a career-outcomes angle rather than a pure exam-mechanics one.
Running realistic, timed practice sets is the most direct way to know where you stand relative to 84/120 before you're sitting in the PSI testing center with the clock running. Working through domain-weighted question sets on the main practice test site lets you simulate the five-hour pressure and the open-book reference lookups together, rather than studying content and timing as separate skills.
FAQ
You need 84 correct answers out of 120 scored questions, which equals 70%. This applies to the full C-1 Plumbing and Heating Contractor trade exam, not the separate CMS business-and-law exam, which uses a 75% standard.
No. PSI may add 1-10 unscored experimental questions to your form, but only the 120 designated scored questions count toward your 84-correct passing requirement. The experimental items still consume your five-hour time limit, though.
No. Only five references are approved in the testing room: UPC 2018, UMC 2018, NFPA 54 (2012), NFPA 58 (2014), and NFPA 13 (2019). Other study materials, handwritten notes, loose papers, and temporary tabs are not permitted at the testing center.
Drain, Waste, and Vents is the single largest domain at 10 items. Gas Systems, Water Supply, Traps and Interceptors, and Isometric Analysis/Plumbing Mathematics each contribute 8 items, together making up more than a third of the 120 scored questions.
Each failed attempt requires a two-week wait before you can retest. If you fail three times, your application is voided and you must restart the Board approval process before scheduling with PSI again.