C-36 Plumbing exam questions, with answers

10 practice questions for the CSLB Plumbing trade exam, each with the answer, a plain explanation and the source it rests on.

From our free C-36 test · Updated 14 October 2026

These are not real exam questions. CSLB does not release its test questions or answer keys, and nobody else has them. We write our own questions from the C-36 outline and the codes, standards and references CSLB lists for the exam. Each answer names its source so you can check it.

The C-36 exam has 5 sections. The questions below are grouped by section, with the share of the exam each one carries. Read the question, pick an answer, then open “Show the answer”. The other questions of the free test, scored section by section, are in the free 25-question C-36 test.

Planning and Estimating · 22% of the exam

Scope of work and code compliance; pipe sizing and venting requirements; shop drawings, plans and specifications; job site inspections; coordination of projects; water conservation; cost estimation for materials, equipment, labor and overhead.

1. A new commercial building has three water systems: drinking water, a nonpotable process water line, and recycled water for toilet flushing. Under the California Plumbing Code, which pipe-marking background colors go with those three systems, in that order?

  1. Green, yellow and purple
  2. Green, purple and yellow
  3. Green, yellow and orange
  4. Blue, yellow and purple
Show the answer

Answer: A. Potable water is marked with white letters on green, nonpotable water with black letters on yellow, and alternate water sources such as recycled water, gray water and rainwater with black letters on purple. Blue is the color stripe for Type L copper tube, not a pipe-marking color, and swapping yellow and purple confuses the two nonpotable systems.

Source: CPC 601.3.1, 601.3.2, 601.3.3, 2025 California Plumbing Code, Title 24 Part 5

2. You are the plumbing contractor on a new office building, and the permanent restrooms will not work for months. The general contractor asks what the plumbing code says about restrooms for the crews until then. Under the California Plumbing Code, what applies?

  1. Nothing applies until the permanent toilets pass final inspection
  2. Facilities are needed only on jobs lasting more than 90 days
  3. Toilet facilities must be provided for workers and kept sanitary
  4. Crews may use the new fixtures once the rough-in passes its test
Show the answer

Answer: C. The plumbing code itself requires toilet facilities for workers during construction and requires that they be kept sanitary. It does not wait for the permanent fixtures to be finished, and it sets no minimum job length. Roughed-in fixtures are not a substitute.

Source: CPC 422.5, 2025 California Plumbing Code, Title 24 Part 5

Underground and Rough Systems · 22% of the exam

Excavation and underground installations; piping layout and installation; fuel gas piping; insulation and system testing.

3. A building sewer made of pipe that is approved for sewers but not for use inside buildings will cross a rural lot that has a private water well and a creek. Which layout meets the California Plumbing Code clearance rules?

  1. 1 ft from the house, 50 ft from the well, 50 ft from the creek
  2. 2 ft from the house, 50 ft from the well, 50 ft from the creek
  3. 2 ft from the house, 50 ft from the well, 25 ft from the creek
  4. 2 ft from the house, 25 ft from the well, 50 ft from the creek
Show the answer

Answer: B. Sewer pipe not approved for use inside buildings must stay at least 2 ft from the building, and the clearance table requires 50 ft from a water well and 50 ft from a stream. The 25-ft well clearance applies only when the sewer is built of pipe approved for use inside buildings, and no reduced distance is given for streams.

Source: CPC 718.3, Table 721.1, 2025 California Plumbing Code, Title 24 Part 5

4. You are checking the drainage fittings on a DWV rough-in before the inspector arrives. Which connection meets the California Plumbing Code?

  1. A double sanitary tee on a stack the same size as its two inlets
  2. A sanitary tee turning the base of a stack into a horizontal drain
  3. A sanitary tee bringing a horizontal branch into a vertical stack
  4. A sanitary tee laid on its back joining two horizontal drains
Show the answer

Answer: C. A sanitary tee is allowed where a horizontal drain enters a vertical one. Horizontal-to-horizontal and vertical-to-horizontal changes need a 45-degree wye or a combination wye and 1/8 bend instead. A double sanitary tee is allowed only when its barrel is at least two pipe sizes larger than the largest inlet.

Source: CPC 706.2, 706.3, 706.4, 2025 California Plumbing Code, Title 24 Part 5

Finish Plumbing Installations · 20% of the exam

Plumbing fixtures and appliances; water heaters; shut-off valves; specialty installations; industrial and commercial piping and sanitary systems.

5. A water heater tank is 60 in tall, and the top of its gas control valve is 10 in above the floor. Under the California Plumbing Code seismic strapping rule, between what heights above the floor may the lower strap go?

  1. From 10 in to 20 in
  2. From 14 in to 30 in
  3. From 14 in to 20 in
  4. From 4 in to 20 in
Show the answer

Answer: C. The lower strap must be in the lower third of the tank height (0 to 60 / 3 = 20 in) and at least 4 in above the controls (10 + 4 = 14 in). That leaves 14 to 20 in. Measuring 4 in from the floor, or using the tank's midpoint, misses one of the two limits.

Source: CPC 507.2, 2025 California Plumbing Code, Title 24 Part 5

6. You are setting a new storage water heater. Which valve arrangement meets the California Plumbing Code?

  1. A shutoff on the cold supply; a gate valve on the T&P discharge pipe
  2. A shutoff on the hot outlet only; no valve on the T&P discharge pipe
  3. A shutoff on the hot outlet; a ball valve on the T&P discharge pipe
  4. A shutoff on the cold supply; no valve on the T&P discharge pipe
Show the answer

Answer: D. The code requires a shutoff valve on the cold water supply to each water heater, and it allows no valve or obstruction in the T&P discharge pipe. A valve on the hot side alone does not meet the shutoff rule, and any valve on the discharge pipe could trap the relief flow.

Source: CPC 606.2, 608.5, 2025 California Plumbing Code, Title 24 Part 5

Service, Repair, and Remodel Plumbing Systems · 19% of the exam

Troubleshooting plumbing issues; isolating leaks and damage; repairing plumbing; retrofitting plumbing; disposal of plumbing materials.

7. A customer complains of banging pipes and dripping faucets. With nothing running, your gauge on a hose bibb reads 95 psi static, and the house has no pressure regulator. What does the California Plumbing Code call for?

  1. A regulator set to 80 psi or less, with an expansion tank ahead of it
  2. A regulator set to 80 psi or less, with an expansion tank after it
  3. A regulator set to 100 psi or less, with an expansion tank after it
  4. No regulator, since 95 psi is under the 150-psi relief valve setting
Show the answer

Answer: B. Static pressure over 80 psi calls for a pressure regulator that brings it to 80 psi or less, and an expansion tank (or engineered relief valve) on the downstream side of the regulator. The 150-psi figure is the maximum relief valve setting, not an allowed working pressure.

Source: CPC 608.2, 608.4, 2025 California Plumbing Code, Title 24 Part 5

8. You are replacing a lavatory P-trap, and the new trap arm comes up a little short. Your helper wants to add a second slip-joint coupling on the outlet side of the trap to make up the length. Under the California Plumbing Code, is that acceptable?

  1. No; only one slip joint is allowed on the trap's outlet side
  2. Yes, as long as both slip joints get new washers and new nuts
  3. Yes, if the added outlet-side slip joint stays exposed and accessible
  4. No; slip joints are allowed only on the inlet side of the trap
Show the answer

Answer: A. The code allows at most one slip joint on the outlet side of a trap, so the arm must be made up another way, for example with a longer arm or a solvent-welded joint. Being accessible or using new washers does not make a second outlet-side slip joint acceptable.

Source: CPC 1003.2, 2025 California Plumbing Code, Title 24 Part 5

Safety · 17% of the exam

Personnel safety; job site safety; environmental safety.

9. In a building's mechanical room, your crew lifts the cover off a floor manhole to reach a sewage vault, and it will stay open while they work below. Under §1632, how must the manhole opening be protected while the cover is off?

  1. With a toeboard only, since the opening is level with the floor
  2. With standard railings around it until the cover goes back on
  3. With cones and caution tape set at least 6 ft back from the edge
  4. With a cover hinged in place so it can be dropped shut quickly
Show the answer

Answer: B. Manhole floor openings are guarded by standard covers, which need not be hinged. While the cover is off, the opening must be protected by standard railings. Cones and tape are not a guard, and a toeboard alone does not stop a person from falling in.

Source: 8 CCR §1632(f), Cal/OSHA Title 8 §1632 Floor, Roof, and Wall Openings to Be Guarded

10. Your service van has no rear windows and no back-up alarm. At a job, plumbers on foot work behind it while it backs up to the pipe rack. Under §1592, which of these meets the rule for this vehicle?

  1. Backing slowly with the hazard flashers turned on the whole time
  2. A single tap of the horn by the driver just before backing
  3. A quick check of the side mirrors before the van starts moving
  4. A spotter in the driver's clear view who directs the backing
Show the answer

Answer: D. For vehicles whose rear view is blocked where workers on foot are exposed, §1592 accepts an automatic back-up alarm, an automatic brake, or administrative controls such as a spotter in clear view of the driver, having the driver walk around the vehicle first, or keeping foot traffic out. A horn, flashers or a mirror check are not on that list.

Source: 8 CCR §1592(b), Cal/OSHA Title 8 §1592 Warning Methods

Where to go from here

How the license works, from experience to fees: how to get a C-36 license. Everything about the course: the C-36 exam page.

Questions from our free C-36 test, written from CSLB License Examination Study Guide, Plumbing (C-36), form 13E-36 (03-2026), for examinations scheduled on or after March 1, 2025. CSLB notes that the percentages are approximate. Reviewed 14 October 2026. Study guidance only; we are not affiliated with CSLB or PSI.

The C-36 exam pageOutline, sample question, course and prices. Free C-36 test25 questions, scored by section. How to get a C-36 licenseExperience, exams, fees and pass rate. What a license costsEvery fee from application to renewal.