The C-36 plumbing trade exam is a closed-book, computer-based, multiple-choice exam with four choices per question, and you get 3½ hours to finish it. To get the license you also have to pass the Law and Business exam, on the same 3½ hours. CSLB does not publish a passing percentage: its own licensing guide says to ask CSLB, because the percentage needed to pass "varies for each exam." So when a website tells you the C-36 has "115 questions" or that you need "72% to pass," know that the number did not come from CSLB.
This page puts every official fact in one place, each one quoted from a CSLB document with a link, so you can stop reading five sites that disagree with each other.
Key facts
| Fact | Value | As of | Source |
|---|---|---|---|
| Time limit | 3½ hours for each exam | 2026-10-15 | CSLB Examinations FAQ |
| Format | Multiple choice, four choices per question, one BEST answer | 2026-10-15 | CSLB C-36 study guide |
| Open or closed book | Closed book. No reference materials may be used | 2026-10-15 | CSLB C-36 study guide |
| Calculator | A calculator will be provided | 2026-10-15 | CSLB C-36 study guide |
| Penalty for guessing | None | 2026-10-15 | CSLB C-36 study guide |
| Passing percentage | Not published; it "varies for each exam" | 2026-10-15 | CSLB, Get Licensed to Build |
| Wait to retake after failing | 21 calendar days | 2026-10-15 | CSLB Examinations FAQ |
| Deadline to pass | 18 months from the day your application is accepted | 2026-10-15 | CSLB Examinations FAQ |
| How long a passed exam counts | Five years | 2026-10-15 | CSLB, Get Licensed to Build |
| Spanish version | Yes, for C-36 and for Law and Business | 2026-10-15 | CSLB Examinations FAQ |
What is on the C-36 trade exam
CSLB's study guide splits the trade exam into five sections and gives each an approximate weight. This is where your study time should go.
| Section | Weight | What it covers |
|---|---|---|
| Planning and Estimating | 22% | Scope of work and code compliance, pipe sizing and venting, plans and specs, inspections, water conservation, cost estimation |
| Underground and Rough Systems | 22% | Excavation and underground installations, piping layout, fuel gas piping, insulation and system testing |
| Finish Plumbing Installations | 20% | Fixtures and appliances, water heaters, shut-off valves, specialty installations, industrial and commercial piping |
| Service, Repair, and Remodel Plumbing Systems | 19% | Troubleshooting, isolating leaks and damage, repair, retrofit, disposal of plumbing materials |
| Safety | 17% | Personnel safety, job site safety, environmental safety |
The study guide's reference list names the 2025 California Plumbing Code, the 2025 California Mechanical Code, the 2025 California Building Code, the 2025 California Green Building Standards Code, the Cal/OSHA safety orders, and the Underground Service Alert rules. You cannot bring any of them into the exam. It is closed book, so what you know is what you have.
What is on the Law and Business exam
Every applicant takes this one too, whatever the trade. It has seven sections:
| Section | Weight |
|---|---|
| Business Organization and Licensing | 13% |
| Business Finances | 15% |
| Employment Requirements | 20% |
| Insurance and Liens | 12% |
| Contract Requirements and Execution | 21% |
| Public Works | 5% |
| Safety | 14% |
How exam day works
- Where: in person at a PSI test center. You cannot take it online. CSLB says PSI has 20 locations in California and 21 locations nationwide that give contractor exams.
- Trade exam location rule: the Law and Business exam can be taken out of state, but all trade exams must be completed in California or Oregon.
- Arrive early: CSLB tells applicants to arrive 30 minutes before the scheduled exam time.
- Bring ID: a valid, government-issued photo ID. Without it, the exam counts as a missed appointment.
- Leave everything else: phones, notes, reading materials, your own calculator and even drinks (including water) are on the prohibited list. A calculator is provided.
- Cancelling: you keep your fee if your cancellation notice reaches PSI two days prior to the scheduled exam date.
Results, retakes and the deadline
You get your result before you leave. At the end of the exam you are given a printed report showing whether you passed or failed.
- If you pass, the report does not show your score. CSLB mails you a Bond and Fee letter with the steps to get the license issued. The pass report is not a license.
- If you fail, the report shows your overall score, including the number of items answered correctly, and you see how well you did on each section. Write those sections down. They match the sections in the tables above.
- Retake wait: candidates who fail are eligible to retake the exam after 21 calendar days, as long as they are not past their 18-month void date. You pay PSI each time you reschedule.
- The deadline: all applications are given 18 months from the day they are accepted to pass the exams. Miss it and the application is void. You submit a new application with new fees.
- Pass one, fail the other: exam results are good for five years, so you only retake the one you failed.
Taking it in Spanish
CSLB offers Spanish versions of 10 exams, and both the C-36 – Plumbing exam and the Law and Business exam are on that list. Candidates who request a translator for those exams are required to take the Spanish versions instead.
Who can sit for the C-36
The person who qualifies the license must be at least 18 years old and have four years of at least journey-level work experience in the last 10 years in the classification applied for. Someone other than you has to verify that experience, such as an employer, a fellow employee or a contractor who observed the work.
What it costs to get licensed
- Application fee: $450 for an original license in a single classification (Business and Professions Code section 7137).
- Exam fees: paid to PSI, not CSLB, and each exam is a separate fee.
- Initial license fee: $200 for a sole owner or $350 for a non-sole owner (good for two years).
- Bond: contractors must post a $25,000 surety bond or cashier's check with CSLB before the license is issued.
What CSLB does not tell you
None of CSLB's study guides, its exam FAQ, or its Get Licensed to Build guide states how many questions are on either exam. Prep companies and forums quote counts and pass marks, but those are their numbers, not the board's. The honest way to prepare is to cover every section in the weights above until you are not guessing.
CSLB also says plainly that there are no schools or application preparation organizations that are affiliated with or agents of CSLB. That includes us. Any school that implies a special line to the board is selling you something.
Common questions
How long is the C-36 exam?
You get 3½ hours to complete the C-36 trade exam, and another 3½ hours for the Law and Business exam. Each is a separate exam with a separate fee. You can take them on the same day or on different days.
What score do you need to pass the C-36?
CSLB does not publish one. Its Get Licensed to Build guide says applicants can ask CSLB about the percentage needed to pass, because it "varies for each exam." If you pass, your report does not show a score at all.
Is the C-36 exam open book?
No. The CSLB study guide says it is a closed-book examination and no reference materials may be used. A calculator will be provided, and you may not bring your own.
How soon can I retake the C-36 if I fail?
After 21 calendar days, as long as you are still inside the 18 months your application gives you to pass. You pay PSI each time you reschedule, and you only retake the exam you failed.
Can I take the C-36 exam online?
No. CSLB says your qualifying examination must be taken in person at one of its PSI locations. The trade exam must be taken in California or Oregon.
Can I take the C-36 exam in Spanish?
Yes. CSLB offers a Spanish version of the C-36 – Plumbing exam and of the Law and Business exam.
Sources
- CSLB Examinations Frequently Asked Questions
- CSLB License Examination Study Guide: Plumbing (C-36)
- CSLB License Examination Study Guide: Law and Business
- CSLB, Get Licensed to Build
- CSLB, Fast Facts: License Bond
- California Business and Professions Code: Contractors State License Law