A valve condition that can cause backflow through a pump is described as which of the following?

• A. Siphon valve
• B. Stuck valve stem
• C. Vent valve
• D. Faulty check valve

Answer: (D)

Backflow through a pump happens when the one-way valve that normally stops reverse flow doesn’t work. A check valve is designed to close automatically to block fluid moving backward from the discharge side into the pump and suction side. If that valve is faulty, it may fail to close properly, allowing backflow and potentially losing prime or causing contamination. The other valves aren’t intended to prevent backflow in normal operation—siphon and vent valves serve different roles, and a stuck valve stem is a general mechanical fault that doesn’t specifically describe a check-valve leakage path. So, the condition described is a faulty check valve because it directly removes the protection against reverse flow.