10 exam-style questions with answers and explanations, straight from our 1,030-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.
The CPDT exam has 100 questions and runs 3 hours 30 minutes.
These 10 free CPDT questions are organized by exam domain, so you can see how each part of the Certified Plumbing Design Technician blueprint is tested. Reveal the answer and explanation under each question.
Domain 1: Set up small projects or a portion of large projects 12% of exam
Question 1
An office renovation may reuse a capped 4-inch branch shown as sanitary drainage on an old record drawing. A site visit confirms the visible stub's size and location, but its destination, invert, and existing connected load have not been verified. The owner wants reuse included in the preliminary basis of design. How should that assumption be recorded?
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Correct answer: A - Carry reuse as conditional on verifying the branch's service, invert, and available capacity.
Domain 2: Collect utility data prior to layout 7% of exam
Question 2
A restaurant's utility-water analysis reports total hardness of 210 mg/L as calcium carbonate. No other water-quality results are included. What conclusion belongs in the equipment-design record?
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Correct answer: C - The water is very hard; heater scale-control and maintenance requirements warrant review.
Domain 4: Lay out general systems 16% of exam
Question 3
After a backflow assembly is added to an office building's water service, downstream pressure rises gradually from 55 to 96 psi during water-heater recovery when no fixtures are used. Opening a faucet promptly returns the pressure to 55 psi. With the heater off, pressure remains steady. Which condition best explains this pattern?
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Correct answer: B - Uncontrolled thermal expansion of water confined downstream of the backflow assembly
Question 4
A hydronic loop requires a direct, pressurized makeup connection from potable water. Its treatment chemical is classified as a health hazard, and a process pump can raise loop pressure above the potable supply pressure. Which device is suitable for both the hazard and the possible backflow mechanisms?
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Correct answer: C - Reduced-pressure-principle backflow prevention assembly
Domain 5: Coordinate with other disciplines 16% of exam
Question 5
An adult wheelchair-accessible public toilet room is being coordinated under the 2010 ADA Standards. All other required clearances and contact protections have been checked. Which recorded dimension requires revision?
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Correct answer: A - Lavatory rim/counter height: 35 inches above the finished floor
Domain 6: Perform sizing calculations 16% of exam
Question 6
A building's controlling outlet requires 30 psi while flowing. At the service connection, static pressure is 78 psi, but the utility confirms a minimum of 57 psi at the 40-gpm design demand. The outlet is 46 ft higher. At that demand, pipe friction consumes 9 psi, the meter 3 psi, and the backflow assembly 7 psi. Use 0.433 psi per foot of water elevation. With the layout and losses unchanged, approximately how much pressure must a booster add at 40 gpm?
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Correct answer: D - About 12 psi at 40 gpm.
Question 7
A natural-gas branch serves a water heater rated at 120,000 Btu/h input with 80% thermal efficiency and a range rated at 80,000 Btu/h input. A separate 60,000-Btu/h oven connects upstream of this branch. The gas heating value is 1,000 Btu/ft3. For the project's governing sizing-table row, capacities are 125 ft3/h for 3/4-inch pipe, 240 ft3/h for 1-inch pipe, and 410 ft3/h for 1-1/4-inch pipe. No diversity allowance applies. Which branch load and smallest listed size should appear in the calculation?
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Correct answer: D - 200 ft3/h; 1-inch pipe
Domain 7: Select equipment 12% of exam
Question 8
A basement toilet group requires a sewage ejector delivering 60 gpm at 28 ft of total dynamic head, with at least 2-inch solids passage. Approved balancing can absorb modest excess head, and electrical and installation requirements are otherwise satisfied. Which offering documents suitable pumping performance and solids handling?
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Correct answer: D - Sewage ejector: 60 gpm at 32 ft of head; 2-inch solids passage
Domain 8: Prepare documentation for submission 5% of exam
Question 9
A permit submission for a parapeted roof shows separate primary and secondary drain inlets and leaders. Inside the building, the leaders join before a single buried storm outlet. The calculations demonstrate adequate inlet and pipe capacities. Under the 2024 IPC secondary-drainage provisions, what correction is still required?
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Correct answer: A - Keep the secondary system separate, discharging above grade where its flow is observable.
Domain 9: Support construction administration 7% of exam
Question 10
During a pre-startup inspection governed by the 2024 IPC, a technician finds a ball valve in a storage water heater's temperature-and-pressure relief discharge line. It was installed for temporary testing and is closed. The heater has not been energized. The installer offers to lock the valve open. What should the technician recommend before startup?
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Correct answer: B - Withhold energization until the valve is removed and the relief discharge path is verified.