PC Preventive Maintenance Procedures 3 — Questions and Answers
Question 1: A plumber performing preventive maintenance notices a gas water heater pilot light frequently extinguishes. What component should be inspected first?
- The gas supply pressure regulator
- The thermocouple (Correct answer)
- The flue draft hood
- The dip tube
Correct answer: The thermocouple
A faulty thermocouple fails to sense the pilot flame and signals the gas valve to shut off, causing the pilot to go out.
Question 2: During preventive maintenance of a grease trap, what measurement determines when it must be pumped?
- When water temperature drops below 60°F
- When combined grease and solids depth reaches 25% of total liquid depth (Correct answer)
- When flow rate decreases by 10%
- When odors become detectable
Correct answer: When combined grease and solids depth reaches 25% of total liquid depth
The 25% rule—combined FOG and solids equaling one-quarter of the trap's liquid depth—is the standard threshold for required pumping.
Question 3: What is the purpose of checking the expansion tank pressure in a closed hydronic system during preventive maintenance?
- To balance flow rates between radiators
- To ensure the pre-charge matches system cold-fill pressure and prevent pressure relief valve discharge (Correct answer)
- To verify boiler fuel consumption rates
- To test the circulator pump capacity
Correct answer: To ensure the pre-charge matches system cold-fill pressure and prevent pressure relief valve discharge
If the expansion tank pre-charge pressure is incorrect, system pressure cannot be absorbed properly, causing the relief valve to discharge.
Question 4: When inspecting flexible supply lines under sinks as part of preventive maintenance, what condition is grounds for immediate replacement?
- Lines that are more than 5 years old regardless of appearance
- Visible corrosion, bulging, or braided wire fraying (Correct answer)
- Lines installed with compression fittings
- Any line longer than 18 inches
Correct answer: Visible corrosion, bulging, or braided wire fraying
Corrosion, bulging, or fraying on braided supply lines indicates imminent failure risk and the line must be replaced immediately.
Question 5: During preventive maintenance, a plumber tests a reduced pressure zone (RPZ) backflow preventer and finds the relief valve discharging continuously. What does this indicate?
- Excessive upstream water pressure
- Check valve No. 2 is leaking and differential pressure is lost (Correct answer)
- The device is functioning normally under high demand
- The relief valve orifice is too small
Correct answer: Check valve No. 2 is leaking and differential pressure is lost
Continuous relief valve discharge in an RPZ indicates that check valve No. 2 is fouled or leaking, collapsing the differential pressure zone.
Question 6: How should a plumber properly dispose of water flushed from a water heater during preventive maintenance that contains high levels of sediment?
- Discharge directly to the nearest storm drain
- Route to a sanitary sewer drain in accordance with local codes (Correct answer)
- Spread on landscaping as fertilizer
- Collect in drums for hazardous waste disposal
Correct answer: Route to a sanitary sewer drain in accordance with local codes
Sediment-laden flush water must be discharged to the sanitary sewer system, not storm drains, to prevent environmental contamination.
Question 7: What is the correct sequence for bleeding air from a hydronic baseboard heating system during preventive maintenance?
- Start at the highest radiator and work downward
- Start at the lowest point and bleed each zone progressively toward the boiler
- Start at the boiler expansion tank and work outward
- Start at the furthest radiator from the boiler and work backward (Correct answer)
Correct answer: Start at the furthest radiator from the boiler and work backward
Bleeding starts at the radiator farthest from the boiler and works back toward it, systematically purging air trapped throughout the system.
PC Preventive Maintenance Procedures 3
A plumber performing preventive maintenance notices a gas water heater pilot light frequently extinguishes.
What component should be inspected first?