CPD Plumbing Systems Design 2 — Questions and Answers
Question 1: According to the IPC, what is the minimum slope required for a 3-inch horizontal drain pipe?
- 1/8 inch per foot
- 1/4 inch per foot (Correct answer)
- 1/2 inch per foot
- 3/8 inch per foot
Correct answer: 1/4 inch per foot
The IPC requires horizontal drain pipes 3 inches and smaller to slope at a minimum of 1/4 inch per foot toward the point of discharge.
Question 2: Which type of water heater arrangement provides the highest first-hour delivery rating?
- Single tank storage unit
- Tankless on-demand heater
- Storage tank with indirect coil
- Multiple tank series arrangement (Correct answer)
Correct answer: Multiple tank series arrangement
Multiple tanks connected in series maximize first-hour delivery rating because successive tanks pre-heat water and increase total storage volume.
Question 3: In a sanitary drainage system, what is the purpose of a cleanout installed at the base of a stack?
- To provide air intake for the stack
- To allow rodding access to clear horizontal drain blockages (Correct answer)
- To prevent backflow from the building sewer
- To reduce noise transmission through the stack
Correct answer: To allow rodding access to clear horizontal drain blockages
A cleanout at the stack base allows maintenance personnel to rod out the horizontal building drain without dismantling pipe connections.
Question 4: What minimum air gap is required between a potable water supply outlet and the flood level rim of a lavatory under ASSE 1012 standards?
- 1 times the supply pipe diameter
- 2 times the supply pipe diameter (Correct answer)
- 3 times the supply pipe diameter
- 4 times the supply pipe diameter
Correct answer: 2 times the supply pipe diameter
ASSE 1012 and most plumbing codes require an air gap of at least twice the supply pipe diameter between the outlet and the flood level rim to prevent backflow.
Question 5: A designer is sizing a medical gas oxygen system. Which document is the primary standard governing the design?
- NFPA 99 (Correct answer)
- ASHRAE 90.1
- IPC Chapter 7
- ASME B31.3
Correct answer: NFPA 99
NFPA 99, Health Care Facilities Code, is the primary standard governing the design, installation, and testing of medical gas and vacuum piping systems.
Question 6: Which pipe material is most appropriate for conveying high-temperature condensate return lines above 200°F in a commercial steam system?
- CPVC Schedule 40
- PEX-A tubing
- Schedule 80 carbon steel (Correct answer)
- ABS DWV pipe
Correct answer: Schedule 80 carbon steel
Schedule 80 carbon steel is rated for high-temperature steam and condensate service and is the standard material for condensate return lines above 200°F.
Question 7: What is the primary function of a pressure-balancing valve in a shower system?
- To boost cold water pressure to the showerhead
- To maintain a constant mixed water temperature regardless of pressure fluctuations (Correct answer)
- To limit maximum flow rate to conserve water
- To prevent hot water from reaching the showerhead above 120°F
Correct answer: To maintain a constant mixed water temperature regardless of pressure fluctuations
A pressure-balancing valve senses pressure changes in the hot and cold supplies and adjusts the ratio to maintain a consistent mixed-water temperature, protecting against scalding or cold shock.
CPD Plumbing Systems Design 2
According to the IPC, what is the minimum slope required for a 3-inch horizontal drain pipe?