Master Plumber Exam Plumbing System Design 2 — Questions and Answers
Question 1: When designing a drainage system for a multi-story building, which factor primarily determines the required diameter of a vertical stack?
- The number of fixture units connected to the stack (Correct answer)
- The height of the building in stories
- The water pressure at the base of the stack
- The material used for the stack pipe
Correct answer: The number of fixture units connected to the stack
Drainage fixture units (DFUs) connected to a stack determine its required diameter per code tables.
Question 2: In a low-pressure hot water heating system, the expansion tank is sized based on which primary factor?
- The BTU output of the boiler only
- The total water volume of the system and temperature rise (Correct answer)
- The pipe diameter of the supply main
- The number of radiators in the system
Correct answer: The total water volume of the system and temperature rise
Expansion tank size is calculated from total system water volume and the expected temperature differential to accommodate thermal expansion.
Question 3: A horizontal drainage branch serving multiple fixtures must have a minimum slope of how many inches per foot according to the IPC for pipes 3 inches and smaller?
- 1/16 inch per foot
- 1/8 inch per foot
- 1/4 inch per foot (Correct answer)
- 1/2 inch per foot
Correct answer: 1/4 inch per foot
The IPC requires a minimum slope of 1/4 inch per foot for horizontal drainage pipes 3 inches in diameter and smaller.
Question 4: Which venting method allows multiple fixtures on the same horizontal branch to share a single vent without individual fixture vents?
- Wet venting
- Air admittance valve venting
- Circuit venting (Correct answer)
- Crown venting
Correct answer: Circuit venting
Circuit venting serves a battery of fixtures on a horizontal branch with one vent at the upstream end, provided certain conditions are met.
Question 5: What is the maximum developed length of a trap arm between the trap weir and the vent pipe for a 1-1/2 inch drain?
- 3 feet
- 5 feet (Correct answer)
- 6 feet
- 8 feet
Correct answer: 5 feet
Per IPC, the maximum trap arm length for a 1-1/2 inch pipe is 5 feet from the trap weir to the vent.
Question 6: In designing a water distribution system using the fixture unit method, a residential lavatory is assigned how many water supply fixture units (WSFU)?
- 0.5 WSFU
- 1 WSFU (Correct answer)
- 2 WSFU
- 4 WSFU
Correct answer: 1 WSFU
A residential lavatory is assigned 1 WSFU per the IPC demand load tables for sizing supply piping.
Question 7: A pressure-reducing valve (PRV) should be installed when the municipal supply pressure exceeds which threshold per the IPC?
- 60 psi
- 80 psi (Correct answer)
- 100 psi
- 120 psi
Correct answer: 80 psi
The IPC requires a PRV when supply pressure exceeds 80 psi to protect fixtures and piping from over-pressurization.
Master Plumber Exam Plumbing System Design 2
When designing a drainage system for a multi-story building, which factor primarily determines the required diameter of a vertical stack?