Practice Test Geeks(PC) Plumber Certification Practice Test
← All PC Flashcard Decks

Troubleshooting & Diagnostics Flashcards

7 cards from real PC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Troubleshooting & Diagnostics flashcards as text

  1. A newly installed backflow preventer on an irrigation system repeatedly loses prime and allows water to back-siphon. The MOST likely cause is:

    Answer: Debris in the check valve seats

    Debris lodged in the check valve seats of a backflow preventer prevents the valves from sealing, allowing back-siphonage under low or negative pressure conditions.

  2. A gas-fired boiler short-cycles (turns on and off rapidly). After confirming correct thermostat settings, the MOST likely cause is:

    Answer: Oversized boiler for the heating load

    An oversized boiler satisfies the thermostat set point before completing a proper burn cycle, causing rapid short-cycling that wastes energy and stresses components.

  3. A plumber pressure-tests a newly installed gas line at 10 PSI with a manometer and observes a slow steady pressure drop over 15 minutes. This indicates:

    Answer: A leak in the system that must be found and repaired

    Any sustained pressure drop during a gas line pressure test indicates a leak; the system must not be put in service until the leak is located and repaired.

  4. After replacing a toilet wax ring, a customer reports the toilet still rocks side to side. The MOST likely cause is:

    Answer: Damaged or uneven closet flange below floor level

    A broken, corroded, or recessed closet flange cannot provide a stable base for the toilet, causing it to rock regardless of wax ring replacement.

  5. A customer has intermittent low hot water pressure only at the kitchen sink. Cold pressure at the same faucet is normal. This MOST likely indicates:

    Answer: Partially blocked hot water port in the faucet cartridge or aerator

    A localized restriction in the hot water side of the faucet — such as a clogged cartridge port or aerator — reduces hot pressure at only that fixture.

  6. A cleanout plug is removed to diagnose a drain blockage. Sewage immediately backs up out of the cleanout opening. This indicates the blockage is located:

    Answer: Downstream of the cleanout toward the municipal sewer

    Sewage backing up at the cleanout confirms the blockage is downstream (toward the street), as wastewater has nowhere to flow and reverses direction.

  7. A building's water pressure is measured at 95 PSI at the meter. Fixtures throughout the building show damage and leaks. The CORRECT corrective measure is to:

    Answer: Install a pressure reducing valve (PRV) set to 60-80 PSI

    Pressure above 80 PSI damages fixtures, valves, and appliances; installing a PRV and setting it within the 60-80 PSI range protects the entire system.