Master Plumber Exam Plumbing Fixtures and Appliances 4 — Questions and Answers
Question 1: Under the International Plumbing Code, what is the minimum clearance from the centerline of a water closet to a side wall or obstruction?
- 12 inches
- 15 inches (Correct answer)
- 18 inches
- 21 inches
Correct answer: 15 inches
The IPC requires a minimum 15-inch clearance from the water closet centerline to any side wall or obstruction.
Question 2: A tankless (on-demand) water heater differs from a storage water heater primarily because it:
- Operates only on natural gas
- Heats water only as it flows through the unit with no storage tank (Correct answer)
- Requires a larger gas supply line than storage heaters
- Cannot supply multiple fixtures simultaneously
Correct answer: Heats water only as it flows through the unit with no storage tank
Tankless water heaters heat water on demand as it flows through a heat exchanger, eliminating standby heat loss associated with storage tanks.
Question 3: A relief valve on a water heater must be set to open at or below which temperature?
- 160°F
- 180°F (Correct answer)
- 200°F
- 212°F
Correct answer: 180°F
Temperature and pressure relief (TPR) valves on water heaters must be set to open at or below 210°F (some codes say 200°F) to prevent dangerous steam buildup.
Question 4: What fitting is NOT permitted for use as the sole trap for a bathtub under most US plumbing codes?
- P-trap
- Deep-seal trap
- Drum trap installed vertically
- S-trap (Correct answer)
Correct answer: S-trap
S-traps are prohibited because they tend to self-siphon due to the downward flow geometry, destroying the water seal.
Question 5: A solar water heating system's backup electric element is classified under plumbing codes as a:
- Potable water appliance requiring no special venting
- Pressure vessel subject to TPR valve requirements (Correct answer)
- Non-potable appliance exempt from plumbing code
- Gray water system component
Correct answer: Pressure vessel subject to TPR valve requirements
Solar water heater storage tanks are pressure vessels and must be equipped with temperature and pressure relief valves per plumbing code.
Question 6: Which urinal type uses little or no water and relies on a chemical sealant trap to block sewer gases?
- Blowout urinal
- Siphon-jet urinal
- Waterless urinal (Correct answer)
- Wall-hung washout urinal
Correct answer: Waterless urinal
Waterless urinals use a floating chemical sealant liquid in the trap that allows urine to pass through but blocks sewer gases from rising.
Question 7: When installing a pedestal lavatory, the supply rough-in height from the finished floor is typically:
- 16 inches
- 20 inches (Correct answer)
- 24 inches
- 30 inches
Correct answer: 20 inches
Supply rough-in for a pedestal lavatory is typically at 20 inches AFF to align with the fixture's internal supply connection.
Master Plumber Exam Plumbing Fixtures and Appliances 4
Under the International Plumbing Code, what is the minimum clearance from the centerline of a water closet to a side wall or obstruction?