- CO-MP Exam Overview: What You're Actually Facing
- Domain-by-Domain Breakdown and Question Weights
- Registration, Fees, and Scheduling Mechanics
- The PSI-Supplied Code Books: 2021 IPC and IRC Rules
- Experience Hours and the Order of Operations
- A CO-MP-Specific Study Timeline
- Test Day Logistics and On-Screen Tools
- After You Pass: CE and Renewal Cycles
- Frequently Asked Questions
- You need 84 of 120 scored questions correct (70%) to pass, per the June 18, 2026 PSI bulletin.
- Sanitary Drainage Systems (22 questions) and Vents (20 questions) carry the most weight - study them first.
- Initial exam cost is $78; a retake costs $73, and payment stays valid for one year.
- The exam uses PSI-supplied 2021 IPC and IRC books - you cannot bring your own references or write in the provided copies.
CO-MP Exam Overview: What You're Actually Facing
The Colorado Master Plumber License Exam (CO-MP) is administered through PSI Services LLC on behalf of the Colorado State Plumbing Board within DORA. It's a computer-based, multiple-choice exam built around 120 scored questions delivered in 270 minutes, with an additional pool of up to 10 unscored questions and 30 extra minutes tacked on for those. You won't know which questions are scored and which are unscored, so every item on screen deserves full attention.
This is not a generic contractor's exam wearing a plumbing costume. It's a code-application test built specifically around Colorado's adopted plumbing standards, and it rewards candidates who can navigate the code book quickly under time pressure rather than candidates who simply memorized isolated facts. If you're still deciding whether this credential is the right target, our ROI analysis of CO-MP certification and salary guide are good starting points before you commit study hours.
Domain-by-Domain Breakdown and Question Weights
The CO-MP exam blueprint spans 11 domains, and the scored-item allocation is fixed and published: 16, 20, 10, 6, 6, 12, 22, 6, 10, 4, and 8 questions respectively. Knowing this distribution changes how you allocate study hours - spending equal time on all 11 domains is a mistake when two of them make up nearly 35% of your score.
Domain 7: Sanitary Drainage Systems (22 questions)
This is the single largest domain on the exam. Expect deep questions on pipe sizing, slope requirements, cleanout placement, and drainage fixture unit calculations pulled directly from the 2021 IPC/IRC.
- Master drainage fixture unit tables and how they scale with pipe diameter
Domain 2: Vents (20 questions)
Second-largest domain. Candidates must distinguish vent types (individual, common, wet, circuit, island) and correctly size vent piping relative to drain connections.
- Practice identifying vent configurations from isometric-style diagrams
Domain 1: Water Supply (16 questions)
Covers pipe sizing for supply lines, water demand calculations, and backflow prevention requirements - a heavily tested area that overlaps with real fieldwork.
- Be fluent in fixture supply demand and water hammer arrestor placement
Domain 6: Storm Drainage Systems (12 questions)
Focuses on roof drainage sizing, area calculations, and secondary drainage provisions - smaller than Sanitary Drainage but still worth dedicated review time.
- Know the difference between primary and secondary storm drain sizing methods
The remaining domains - Fixtures and Equipment (10), General Regulations (6), Traps/Interceptors/Separators (6), Indirect and Special Waste Piping (6), Isometric Analysis (10), Residential Fire Sprinklers (4), and Water Heaters (8) - round out the blueprint. Residential Fire Sprinklers is the lightest domain at just 4 questions, so while you shouldn't ignore it, it shouldn't consume disproportionate study time either. For a full walkthrough of every domain with study priorities, read our complete guide to all 11 content areas.
| Domain | Scored Questions |
|---|---|
| Sanitary Drainage Systems | 22 |
| Vents | 20 |
| Water Supply | 16 |
| Storm Drainage Systems | 12 |
| Fixtures and Equipment | 10 |
| Isometric Analysis | 10 |
| Water Heaters | 8 |
| General Regulations | 6 |
| Traps, Interceptors, and Separators | 6 |
| Indirect and Special Waste Piping | 6 |
| Residential Fire Sprinklers | 4 |
Registration, Fees, and Scheduling Mechanics
The initial CO-MP exam fee is $78. If you don't pass on the first attempt, a retake costs $73. Once you've paid, that payment stays valid for one year, so plan your retake window accordingly rather than letting it lapse. These numbers matter when budgeting for licensure - see our full certification cost breakdown for how this fits into the total investment.
Scheduling is handled through PSI, and both English and Spanish testing are available. If you need accommodations, PSI supports ESL candidates with time-and-a-half extended time and a qualifying translation dictionary - arrange these before your scheduled date, not the week of. For specific testing windows and deadlines, check our exam dates and scheduling guide.
Key Takeaway
Because retake payments are cheaper ($73 vs. $78) and remain valid for a year, a failed first attempt isn't catastrophic financially - but it does cost you time toward licensure, so treat your first sitting as the one to prepare for seriously.
The PSI-Supplied Code Books: 2021 IPC and IRC Rules
One of the most misunderstood parts of CO-MP prep is the reference material policy. PSI supplies the 2021 International Plumbing Code (IPC) and 2021 International Residential Code (IRC) at the testing center. You are not allowed to bring your own copies, formula sheets, or personal notes, and you cannot write in, highlight, underline, or index the provided books in any way.
This means your study strategy needs to build genuine navigation speed inside a clean, unmarked code book. If your only prep method has been flipping through a heavily tabbed personal copy, you'll be caught off guard on test day. Practice locating sections cold, using only the table of contents and index that ship with the book.
Because the code edition and passing standard are both things PSI has updated before, don't rely on secondhand summaries floating around forums. Cross-check details against the official bulletin every time you schedule, and lean on resources like our one-page cheat sheet of must-know facts only as a supplement, not a substitute, for the bulletin.
Experience Hours and the Order of Operations
A detail that trips up many candidates: passing the CO-MP exam does not, by itself, establish your experience eligibility for licensure. Master licensure requires 8,500 verified practical-experience hours, and critically, you cannot verify your own experience - someone else (typically a supervising licensed plumber or employer) has to sign off on those hours.
The recommended order of operations is to take the examination before applying for the license, then separately satisfy the experience verification requirement. Don't assume that passing the exam means you're automatically eligible to apply - the two tracks run in parallel, not in sequence tied to the test itself. Full eligibility mechanics, including how the 8,500 hours get documented, are covered in our CO-MP requirements guide.
A CO-MP-Specific Study Timeline
Generic study techniques like spaced repetition or timed practice blocks only help if they're pointed at the right material in the right order. Given the domain weighting, here's how to structure a multi-week runway toward your exam date.
Sanitary Drainage Systems & Vents
- Drill drainage fixture unit tables and vent sizing charts from the 2021 IPC - these two domains alone are 42 of 120 questions
- Practice unmarked-book navigation for drainage and venting chapters
Water Supply & Isometric Analysis
- Work through water demand calculations and backflow prevention scenarios
- Practice reading isometric diagrams to identify pipe runs, vents, and fixture connections
Storm Drainage, Fixtures, Water Heaters
- Cover roof drain sizing and secondary drainage provisions
- Review fixture and water heater installation clearances and code requirements
Smaller Domains & Timed Practice
- Cover General Regulations, Traps/Interceptors/Separators, Indirect Waste Piping, and Fire Sprinklers
- Run full-length timed practice sessions to build stamina for the 270-minute window
If you want a general sense of how difficult candidates find this exam relative to the time invested, our difficulty guide and pass rate analysis give useful context without inflating expectations. You can also run realistic timed practice on our practice test platform to simulate the pacing of 120 questions across 270 minutes.
Test Day Logistics and On-Screen Tools
On exam day, you'll have access to an on-screen calculator - you don't need to bring your own, and personal calculators aren't permitted anyway. Combined with the prohibition on personal formula sheets, this means all your calculation methods need to be internalized, not looked up.
Budget your 270 minutes across 120 scored questions realistically: that's roughly 2.25 minutes per question, but drainage and venting problems involving table lookups will eat more time than straightforward regulation questions. If unscored pretest items are mixed in, they'll extend your session by up to 30 minutes, so don't panic if your allotted time feels longer than expected once you're seated.
Key Takeaway
Practice every code-lookup calculation using only the on-screen calculator and an unmarked code book copy - that's exactly what you'll have in the testing room.
After You Pass: CE and Renewal Cycles
Passing the CO-MP exam is a milestone, not the finish line for staying licensed. Renewal requires 8 continuing education hours each year, totaling 16 hours across the March 1, 2025 to February 28, 2027 cycle. If you're a first-time licensee by examination, you're exempt from CE requirements until your first renewal - a helpful grace period while you get established.
Looking further ahead, three-year renewal terms begin March 1, 2027, which changes the CE cadence going forward. Keep this on your radar so you're not caught off guard by a compliance deadline shortly after licensure.
If you're still mapping out what this credential means for your career trajectory or how it compares across naming conventions people search for, our companion pieces - What Is CO-MP?, CO-MP Meaning, and What Does CO-MP Stand For? - cover the fundamentals. For training pathway options before you sit the exam, see CO-MP Training.
Frequently Asked Questions
There are 120 scored questions with 270 minutes to complete them, plus up to 10 unscored questions that add 30 additional minutes if included in your session.
You need 70%, or 84 correct out of 120 scored questions, based on overall performance rather than domain-specific minimums, per the June 18, 2026 PSI bulletin.
No. PSI supplies the 2021 IPC and IRC at the testing center, and you cannot write in, highlight, underline, or index them. Personal reference books and formula sheets are prohibited.
Not automatically. Master licensure also requires 8,500 verified practical-experience hours verified by someone other than yourself. Take the exam before applying for the license, since passing alone doesn't establish experience eligibility.
The initial exam fee is $78, and a retake costs $73. Payment remains valid for one year from when it's made.