CSLB General Building (B) Trade Practice Test
Frequently asked questions
How many Master Plumber (UPC/IPC) practice questions are here?+
A full bank of original Master Plumber (UPC/IPC) practice questions across the official content areas, weighted like the real exam, with explanations. Free, no signup.
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About 100 questions, 300 minutes, and you need 75% to pass. Practice by topic here, then take the full timed mock exam to gauge readiness.
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Sample practice questions
A few real questions from this free bank, with full explanations. Use the practice tool above for the whole set.
- 1. Design & Sizing
A residential branch serves the following fixtures with these water-supply fixture unit (WSFU) values: 8 water closets (tank) at 2.5 each, 8 lavatories at 1 each, and 8 showers at 2 each. What is the total demand load on the branch?
- a.52 WSFU
- b.36 WSFU
- c.44 WSFU
- d.60 WSFU
Answer: a
Explanation: Multiply each fixture count by its WSFU value and add: (8 x 2.5) + (8 x 1) + (8 x 2) = 20 + 8 + 16 = 52 WSFU. This total is what you carry into a Hunter-curve demand chart to convert fixture units to gpm. Using the wrong per-fixture value is the usual cause of a low answer such as 44.
Source: UPC §610.0
- 2. Design & Sizing
A vent must be sized at not less than one-half the diameter of the drain it serves, and never smaller than 1-1/4 in. What is the minimum vent size for a 3 in drain?
- a.1-1/4 in
- b.2 in
- c.3 in
- d.1-1/2 in
Answer: d
Explanation: Half of 3 in is 1-1/2 in, which is larger than the 1-1/4 in floor, so the minimum vent is 1-1/2 in. The half-diameter rule sets the size and the 1-1/4 in minimum only governs very small drains. A 4 in drain by the same rule would need at least a 2 in vent.
Source: UPC §904.1
- 3. Design & Sizing
A recirculation loop must deliver 6 gpm of hot water. Using v = 0.408 x Q / d^2, what inside diameter keeps the velocity at about 2 ft/s to limit erosion of the continuously circulated hot line?
- a.0.75 in
- b.1.50 in
- c.1.10 in
- d.2.00 in
Answer: c
Explanation: Solve for d: d = sqrt(0.408 x Q / v) = sqrt(0.408 x 6 / 2) = sqrt(1.224) = 1.11 in. Hot recirculation lines are held to a low velocity, near 2 to 3 ft/s, because constant flow at high velocity erodes copper. A larger diameter lowers velocity for the same flow.
Source: UPC §610.0
- 4. Systems & Code
A commercial kitchen installs a grease interceptor rated for a flow of 35 gpm. Using the common rule that grease capacity in pounds is about twice the gpm rating, what nominal grease retention does this unit provide, and what is its purpose?
- a.35 lb, to trap sand
- b.70 lb, to intercept fats, oils and grease
- c.150 lb, to neutralize acid
- d.300 lb, to settle solids
Answer: b
Explanation: A hydromechanical grease interceptor rated at 35 gpm provides roughly 70 lb of grease retention and its purpose is to intercept fats, oils, and grease before they enter and clog the building drain and public sewer. Interceptors are sized by fixture flow and required retention. Sand interceptors and acid neutralizers serve entirely different wastes.
Source: IPC §1003.4
- 5. Systems & Code
A water softener regenerates using 8 lb of salt per cubic foot of resin for a 3 cubic foot resin bed. How much salt is consumed per regeneration cycle?
- a.24 lb
- b.8 lb
- c.16 lb
- d.32 lb
Answer: a
Explanation: Salt per regeneration = dosage x resin volume = 8 lb/ft^3 x 3 ft^3 = 24 lb. The salt dose sets both the operating cost and the chloride load in the brine discharge, which must terminate through an air gap to a receptor. Higher salt doses increase capacity but also increase brine strength.
Source: UPC §611.0
- 6. Systems & Code
A boiler feed with chemical treatment connects to potable water. This is a high-hazard connection. Which assembly protects the potable supply against backpressure from the pressurized boiler?
- a.Atmospheric vacuum breaker
- b.Dual check valve
- c.Hose-bibb vacuum breaker
- d.Reduced-pressure principle backflow assembly
Answer: d
Explanation: A chemically treated boiler is a high health hazard under backpressure, so a reduced-pressure principle assembly is required because it alone protects against backpressure of a health hazard. Atmospheric vacuum breakers cannot be used under continuous pressure or against backpressure. The RP relief port provides a visible, fail-safe break.
Source: UPC §603.5.7
- 7. Gas & Fuel
A propane branch must deliver a 75,000 BTU/hr appliance at a longest length of 40 ft. Propane is 2,500 BTU/ft^3. The 40 ft table lists 1/2 in = 45 cfh and 3/4 in = 95 cfh. What is the required cfh and minimum pipe size?
- a.18 cfh, 1/2 in
- b.24 cfh, 1/2 in
- c.30 cfh, 1/2 in
- d.30 cfh, 3/4 in
Answer: c
Explanation: cfh = 75,000 / 2,500 = 30 cfh, which is within the 45 cfh capacity of 1/2 in pipe at 40 ft, so 1/2 in is adequate. Because propane carries 2.5 times the energy per cubic foot of natural gas, the required cfh and pipe size are smaller for the same BTU load. Always convert BTU to cfh using the correct heating value for the fuel.
Source: IFGC §402.4
- 8. Administration
A DWV rough-in is water tested. The test fills the system with water to create a 10 ft head at the lowest point. Using 0.433 psi per foot, what pressure does a 10 ft water column exert at the base, and what does the test prove?
- a.2.3 psi, that vents are clear
- b.4.33 psi, that joints hold under head with no leaks
- c.10 psi, that slope is correct
- d.0.43 psi, that traps are set
Answer: b
Explanation: A 10 ft column exerts 10 x 0.433 = 4.33 psi at the base, and holding that head for the required time proves every joint below the fill line is watertight. The water (or an equivalent air) test is applied before the piping is concealed. A dropping level indicates a leak to be located and repaired.
Source: UPC §712.0
- 9. Administration
An inspector finds that a backflow assembly was installed but never tested by a certified tester. What documentation closes this item?
- a.A passing test report from a certified backflow tester filed with the jurisdiction
- b.The installer's invoice
- c.A photo of the device
- d.The permit card alone
Answer: a
Explanation: A newly installed backflow assembly must be tested by a certified backflow tester and the passing test report filed with the water purveyor or jurisdiction to prove it functions. The device's presence alone is not sufficient; performance must be verified and recorded. Annual re-testing is typically required thereafter.
Source: UPC §103.5
- 10. Safety
A plumber replaces piping in a building constructed before 1978 and disturbs old painted surfaces and solder. What two legacy hazards require specific precautions?
- a.Asbestos and radon
- b.Silica and mold
- c.Formaldehyde and PCBs
- d.Lead (paint and old solder) and asbestos (pipe insulation and old sheet materials)
Answer: d
Explanation: Pre-1978 buildings commonly contain lead paint and lead solder plus asbestos in pipe insulation, transite, and floor and sheet materials, both of which require specific handling, containment, and disposal rules. Lead solder was banned for potable use in 1986, and asbestos insulation must not be disturbed without proper controls. Both are serious long-term health hazards.
Source: EPA/OSHA lead