- CO-MP is the Colorado Master Plumber License Exam, administered by DORA's State Plumbing Board via PSI Services.
- You need 84 of 120 scored questions correct (70%) to pass, per the June 18, 2026 PSI bulletin.
- The exam draws from the PSI-supplied 2021 IPC and IRC - no personal codebooks, notes, or highlighting allowed.
- Master licensure requires 8,500 verified practical-experience hours that someone else must confirm, not the applicant.
What Is a CO-MP?
CO-MP stands for the Colorado Master Plumber License Exam - the credentialing test that Colorado requires plumbers to pass before they can be licensed to design, supervise, and take full legal responsibility for plumbing systems at the master level. It is not a generic industry certification you can pursue independently of state regulation; it is a regulatory exam tied directly to Colorado's licensing statute and administered as a gateway to master-level plumbing authority in the state.
If you've landed here after seeing "CO-MP" used to describe something else online, be careful: that abbreviation is reused by other unrelated credentialing programs elsewhere. On this site, and in this article, CO-MP refers exclusively to the Colorado Master Plumber License Exam described in the official PSI candidate bulletin and Colorado's plumbing regulations. For a deeper dive into terminology and how the acronym is used across contexts, see CO-MP Meaning and What Does CO-MP Stand For?.
Who Administers the Exam
The exam is overseen by the Colorado State Plumbing Board, part of the Department of Regulatory Agencies (DORA). Actual test delivery - scheduling, proctoring, scoring, and bulletin publication - is handled by PSI Services LLC, a third-party testing vendor used by many state licensing boards. The regulatory authority behind Master Plumber licensure sits in 3 CCR 720-1, the state's plumbing rules, while PSI's candidate bulletin governs the day-to-day mechanics of the exam itself.
This two-party structure matters for candidates: eligibility, experience-hour verification, and license issuance run through DORA, while exam content, format, and scoring rules run through PSI. When you register, you're dealing with PSI's system; when you apply for the license itself, you're dealing with DORA. For a full walkthrough of what's required before you can even sit for the exam, see CO-MP Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Exam Format and Scoring
The CO-MP is delivered as a computer-based, multiple-choice exam. Candidates answer 120 scored questions in 270 minutes, with the possibility of up to 10 additional unscored (pretest) questions tacked on with 30 extra minutes. You won't know which items are scored and which are unscored, so every question should be treated as if it counts.
According to the June 18, 2026 PSI bulletin, the passing standard is 70%, or 84 out of 120 scored questions, based on overall performance across the exam rather than domain-by-domain minimums. That means you can afford to be weaker in a low-weight domain like Isometric Analysis if you're strong across the higher-weight ones - but you still need a broad base of competency because no single domain carries enough weight to carry the whole score. For the exact numeric breakdown and what it means for your study plan, see CO-MP Passing Score 2026: Exactly What You Need to Pass.
Key Takeaway
Because passing is based on overall performance, not per-domain thresholds, don't ignore small domains entirely - a handful of easy points in a 4- or 6-question domain still moves your total score.
Reference Materials Allowed During Testing
The CO-MP has a dedicated reference section built into the testing environment. Candidates use a PSI-supplied 2021 IPC and IRC - you cannot bring your own codebooks, and you cannot write in, highlight, underline, or index the copies provided at the test center. Personal reference books and formula sheets are prohibited outright. An on-screen calculator is provided for any math-based questions, so you don't need to bring one.
One nuance worth flagging: the bulletin's introductory language still references 2018 codes in places, even though the dedicated reference section specifies the 2021 IPC and IRC. Colorado amendments to the code are not tested. Because code editions and passing standards can shift between bulletin updates, always confirm the current supplied edition and passing score directly with PSI when you schedule your seat.
The 11 Exam Domains
The CO-MP tests 11 distinct content domains, each with an official scored-item allocation. Understanding these weights is the single most useful thing you can do before you start studying, because it tells you exactly where your time pays off.
| Domain | Scored Questions |
|---|---|
| 1. Water Supply | 16 |
| 2. Vents | 20 |
| 3. Fixtures and Equipment | 10 |
| 4. General Regulations | 6 |
| 5. Traps, Interceptors, and Separators | 6 |
| 6. Storm Drainage Systems | 12 |
| 7. Sanitary Drainage Systems | 22 |
| 8. Indirect and Special Waste Piping | 6 |
| 9. Isometric Analysis | 10 |
| 10. Residential Fire Sprinklers | 4 |
| 11. Water Heaters | 8 |
Sanitary Drainage Systems is the largest domain at 22 questions, followed closely by Vents at 20. Together these two domains account for nearly 35% of the entire scored exam, which makes them non-negotiable study priorities. For a domain-by-domain breakdown of what each content area actually covers on test day, see CO-MP Exam Domains 2026: Complete Guide to All 11 Content Areas.
Sanitary Drainage Systems (22 questions)
This is the exam's heaviest domain and covers how waste and drain lines are sized, sloped, connected, and vented into the sanitary system as a whole.
- Sizing drainage piping based on fixture units
- Proper slope and grade requirements
- Cleanout placement and access requirements
Vents (20 questions)
The second-largest domain, testing your understanding of how venting systems prevent trap siphonage and maintain proper drainage flow.
- Vent sizing and distance-to-trap limits
- Wet venting, common venting, and combination waste-and-vent systems
- Vent termination requirements
The remaining domains - Water Supply, Fixtures and Equipment, Storm Drainage Systems, Isometric Analysis, and Water Heaters among them - are lighter in point value individually, but collectively they still represent well over half the exam. Skipping any of them because they seem "small" is a common mistake; see How Hard Is the CO-MP Exam? Complete Difficulty Guide 2026 for a closer look at where candidates typically underestimate the material.
Eligibility and Experience Hours
Passing the CO-MP is a necessary step toward Master Plumber licensure, but it is not sufficient on its own. Colorado requires 8,500 verified practical-experience hours for master-level licensure, and critically, applicants cannot verify their own experience - someone else with standing to attest to your work history has to sign off on those hours.
Also important: you're expected to take the examination before applying for the license, but passing the exam does not by itself establish that you're experience-eligible. In other words, passing CO-MP and satisfying the hours requirement are two separate tracks that both need to be cleared before DORA will issue a Master Plumber license. Candidates sometimes assume a passing score is the finish line - it isn't. The full eligibility picture, including how experience hours get documented and verified, is covered in CO-MP Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Fees, Scheduling, and Testing Rules
The initial CO-MP exam attempt costs $78. If you don't pass on the first try, a retake costs $73. Payment for an exam attempt is valid for one year, so candidates who register but delay scheduling need to keep that expiration window in mind. For a complete cost breakdown, including how retake fees stack up if you need multiple attempts, see CO-MP Certification Cost 2026: Complete Pricing Breakdown.
Scheduling is done through PSI's testing system, and since bulletins get updated periodically - including changes to code editions and passing standards - it's worth double-checking the current bulletin at scheduling time rather than relying on older information. Details on testing windows and how far in advance to book are covered in CO-MP Exam Dates 2026: Testing Windows, Deadlines & Scheduling.
Licensure, CE, and Renewal Cycles
Once licensed, Master Plumbers in Colorado must complete continuing education to maintain their license. The requirement is eight CE hours each year, which totals 16 hours across the March 1, 2025 to February 28, 2027 cycle. There's a helpful exemption built in: first-time licensees who obtained their license by examination are exempt from CE until their first renewal, giving newly licensed plumbers some breathing room before the clock starts.
Looking ahead, Colorado is shifting toward longer renewal terms - three-year renewal cycles begin March 1, 2027. This is a structural change candidates should be aware of if they're timing their licensure around renewal deadlines, since the CE math and renewal cadence will look different after that transition point.
Who Actually Needs This Credential
The CO-MP matters to anyone pursuing Master Plumber status in Colorado - typically experienced journeyman plumbers who have accumulated enough verified field hours and are ready to take on the legal and supervisory responsibilities that come with a master license, including pulling permits, supervising crews, and signing off on plumbing designs. Employers in commercial construction, mechanical contracting, and plumbing design frequently require or strongly prefer Master Plumber licensure for senior roles, project oversight, and business ownership paths.
If you're weighing whether pursuing this license is worth the time and cost relative to staying at journeyman level, it helps to look at the bigger career picture rather than just the exam itself. See Is the CO-MP Certification Worth It? Complete ROI Analysis 2026 and CO-MP Salary Guide 2026: Complete Earnings Analysis for context, and CO-MP Jobs for a sense of what roles typically call for this license.
How to Approach Preparation
Preparation for the CO-MP works best when it's mapped directly to the domain weights rather than treated as a generic "study the whole codebook" exercise. Since Sanitary Drainage Systems and Vents together make up 42 of the 120 scored questions, those two domains deserve the earliest and heaviest attention in any study calendar.
Sanitary Drainage Systems and Vents
- Work through drainage sizing, slope, and cleanout rules using the 2021 IPC/IRC
- Master vent sizing, wet venting, and termination requirements
- Practice questions exclusively from these two domains before moving on
Water Supply, Storm Drainage, and Fixtures
- Cover mid-weight domains (16, 12, and 10 questions respectively)
- Build fluency reading isometric drawings for the related domain
- Mix in review of the earlier heavy domains to prevent forgetting
Remaining Domains and Full Simulations
- Finish General Regulations, Traps/Interceptors/Separators, Indirect Waste Piping, Fire Sprinklers, and Water Heaters
- Run full-length timed practice exams under the 270-minute limit
- Review any domain where accuracy consistently lags
Because you won't have access to your own notes or a formula sheet on exam day, your practice should mimic real conditions: working problems using only the 2021 IPC/IRC and an on-screen-style calculator, not a personal binder of tabbed references. For a structured, week-by-week plan built specifically around this exam's domain weighting, see CO-MP Study Guide 2026: How to Pass on Your First Attempt. And if you want a fast final review before test day, the CO-MP Cheat Sheet 2026: One-Page Review of Must-Know Facts condenses the highest-yield facts into one page.
Running full-length timed practice sessions is one of the most reliable ways to gauge readiness, since it exposes both content gaps and pacing issues before they cost you on exam day. You can build that familiarity using realistic practice questions on the CO-MP Exam Prep practice test platform, which mirrors the domain distribution and question style of the real exam.
Key Takeaway
Don't split study time evenly across all 11 domains. Allocate time roughly in proportion to scored-question counts - Sanitary Drainage Systems and Vents first, smaller domains last.
Frequently Asked Questions
On this site, CO-MP refers to the Colorado Master Plumber License Exam, administered by PSI Services on behalf of Colorado's DORA State Plumbing Board. For more on the terminology itself, see What Is CO-MP? and What Does CO-MP Mean?.
There are 120 scored multiple-choice questions administered in 270 minutes, plus up to 10 unscored questions with an additional 30 minutes allowed.
Per the June 18, 2026 PSI bulletin, you need 70%, or 84 out of 120 scored questions correct, based on overall performance rather than per-domain minimums.
No. PSI supplies a 2021 IPC and IRC at the testing center for reference. You cannot write in, highlight, underline, or index these copies, and personal reference books or formula sheets are not permitted.
No. Passing the exam is one requirement, but Master Plumber licensure also requires 8,500 verified practical-experience hours confirmed by someone other than yourself. Passing the exam does not establish experience eligibility on its own.