Free practice questions for the California CSLB C-36 Plumbing trade exam — with a written explanation on every answer, in English, Spanish, and Russian.
The C-36 Plumbing exam is the trade exam California requires of plumbing contractor applicants, administered for the CSLB by PSI. The official CSLB study guide splits it into five weighted sections: planning and estimating, underground and rough systems, finish plumbing installations, service and repair, and safety. Practice it below — free, no sign-up, with a written explanation on every question. Every C-36 applicant also takes the CSLB Law and Business exam.
No account needed. Pick an answer to see whether it's right and read the explanation — the same explanations you get on every question in the full course.
Every question tells you why the correct answer is correct and defines the terms it uses — so you learn the rule, not just the answer.
Questions are written from scratch against the official codes and agency publications for this exam — never copied from the real exam.
Every question and explanation is fully translated, with the English exam term kept alongside — not a shallow machine translation.
LICENA is a practice tool, not a school. We don't promise a pass — we help you understand the material and walk in prepared.
The full C-36 Plumbing course is 500 questions across 5 blocks, drawn from these five official sections and weighted the way the exam weights them.
The C-36 is CSLB's trade exam for plumbing contractors: it assumes you can already do the work and checks whether you do it to California code, on budget, and safely. The official study guide splits it into five weighted sections, and a practice test worth your time follows those weights. Here is what each section asks, and where candidates slip.
Scope of work and code compliance, pipe sizing and venting, plans and specifications, jobsite inspections, coordination, water conservation, and cost estimation. Two things trip people up. The water-conservation numbers are California's, not the federal ones: the effective flush volume of a water closet may not exceed 1.28 gallons, and a wall-mounted urinal is capped at 0.125 gallons per flush — the 1.6-gallon figure many study sheets still print is the old federal limit. And the math is arithmetic, not algebra, but it punishes skipped steps: read whether a markup applies to materials only or to the whole bid. A calculator is provided at the test center.
Excavation and underground installation, piping layout, fuel gas piping, insulation, and testing. Deadlines and pressures dominate. Before you dig, Government Code §4216.2 requires you to delineate the area and notify the regional notification center — the 811 dig-alert service — at least two working days and not more than 14 calendar days ahead; the ticket is good for 28 days. Horizontal drainage runs at a uniform slope of not less than a quarter inch per foot, with an eighth of an inch allowed only on pipe 4 inches and larger, and only with local approval. Ordinary low-pressure gas piping is tested with air, carbon dioxide, or nitrogen at not less than 10 psi held at least 15 minutes; welded piping and systems above 14 inches water column jump to 60 psi for 30 minutes.
Fixtures and appliances, water heaters, shut-off valves, specialty work, and commercial or industrial sanitary piping. Water heaters carry the most trap-laden detail: California requires the tank strapped against earthquake movement, with restraint in the upper and lower third of the tank and the lower strap at least 4 inches above the controls. Temperature-and-pressure relief discharge piping runs full size and downward with no valve in it, and terminates outside between 6 inches and 2 feet above grade; discharging into the water heater's drain pan is specifically prohibited. Fixture setting has its own numbers: a water closet no closer than 15 inches from centerline to a side wall, with 24 inches of clear space in front.
Troubleshooting, isolating leaks, repairs, retrofits, and disposal of removed material. The exam favours diagnosis over parts lists, so learn the symptom-to-cause chains. Sewer-gas odour plus gurgling and slow drainage at a fixture used every day is a venting problem — the drain is siphoning the trap seal out because the vent is blocked — not evaporation, which only explains odour at an unused fixture. Remember the seal is 2 to 4 inches deep, and that S-traps, bell traps, and crown-vented traps may not be installed at all. Vents rise 6 inches above the fixture's flood-level rim before turning horizontal, and terminate 6 inches above the roof and 10 feet from, or 3 feet above, any openable window or air intake.
Personnel, jobsite, and environmental safety, drawn from Cal/OSHA's Construction Safety Orders. Trenching dominates. A protective system — shoring, shielding, or sloping — is required in any excavation 5 feet or deeper unless it is entirely in stable rock, and Cal/OSHA separately requires a permit for any trench 5 feet or deeper a person must enter. A trench 4 feet or deeper needs a ladder, ramp, or stairway within 25 feet of lateral travel, and spoil piles stay at least 2 feet back from the edge. If you are also preparing for the CSLB Law & Business exam or a companion trade such as C-10 Electrical, the same Cal/OSHA logic reappears there.
You take the C-36 on a computer at a PSI testing center, closed book, with 3.5 hours per exam — the limit published in CSLB's official Examinations FAQ. Every question is multiple choice with four options and one best answer; some require calculation, and a calculator is provided. There is no penalty for guessing, so never leave an item blank. You get a printed pass/fail report before you leave; a failing report shows your overall score and how many items you answered correctly. You may retake after 21 calendar days, paying PSI a re-examination fee, within your application's 18-month window. C-36 is one of the ten exams CSLB publishes in an official Spanish version.
The LICENA C-36 course is 500 questions across 5 blocks. At 30 questions a day that is about three weeks: two passes with time to re-drill your weakest block. Weight your effort as the exam does: planning and underground work are 22% each, noticeably more than safety at 17%. Read the explanation on every miss; the exam rewords facts, so memorising answer letters does nothing, while knowing why a relief line must terminate above grade and pointing down carries across any wording. Pair the practice with CSLB's free official C-36 study guide and the current California Plumbing Code, and treat any guaranteed-pass promise as a warning sign.
The full 500-question C-36 bank across 5 blocks, with a written explanation on every answer, weak-area practice and a timed final exam, in EN·ES·RU. California exam-prep schools list programs from about $250 to $1,200 — this is $20/month, on your phone, cancel anytime.
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LICENA provides online practice only. Registration, exam scheduling and licensing are handled by the CSLB and its exam vendor PSI — not by LICENA. LICENA is not affiliated with the CSLB or PSI.