A plumber is troubleshooting a toilet that continuously runs after flushing. Upon inspection, it is determined that the flapper valve is not sealing properly. Which of the following is the most likely cause of this issue?

Question: A plumber is troubleshooting a toilet that continuously runs after flushing. Upon inspection, it is determined that the flapper valve is not sealing properly. Which of the following is the most likely cause of this issue?

Answer options:

• The water level in the tank is too low.
• The fill valve is continuously allowing water into the tank.
• The flapper chain is too short, preventing full closure. ✅ Sediment or damage on the flapper or the flush valve seat.

Correct answer: Sediment or damage on the flapper or the flush valve seat.

Explanation: Continuous running of a toilet due to a flapper not sealing properly is most commonly caused by sediment build-up or damage on the flapper itself or the flush valve seat, preventing a tight seal. A low water level would not cause the flapper to fail, a faulty fill valve would cause overfilling, and a short chain would prevent complete opening, not proper closing.