PC Preventive Maintenance Procedures 3

Question 1

A plumber performing preventive maintenance notices a gas water heater pilot light frequently extinguishes. What component should be inspected first?

Accepted Answer

The thermocouple

Answer

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?

Accepted Answer

When combined grease and solids depth reaches 25% of total liquid depth

Answer

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?

Accepted Answer

To ensure the pre-charge matches system cold-fill pressure and prevent pressure relief valve discharge

Answer

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?

Accepted Answer

Visible corrosion, bulging, or braided wire fraying

Answer

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?

Accepted Answer

Check valve No. 2 is leaking and differential pressure is lost

Answer

Continuous relief valve discharge in an RPZ indicates that check valve No. 2 is fouled or leaking, collapsing the differential pressure zone.

(PC) Plumber Certification Practice Test

(PC) Plumber Certification Practice Test

PC Preventive Maintenance Procedures 3