What is a clapper valve?

• A. Opens when the system flows water from the supply side and also opens the pumping to retard the chamber
• B. Remains closed under normal operation and opens only on demand
• C. Vent air from the system as needed
• D. Blocks water flow until manual release

Answer: (A)

A clapper valve is a one-way valve with a hinged disc (the clapper) that swings open to allow forward flow and closes to prevent reverse flow. It opens when water moves in the intended direction from the supply into the system, and then closes to block any backflow, helping keep the pump primed and preventing water from returning into the pumping chamber. This behavior matches the idea that it opens with forward flow from the supply and prevents backflow into the pump, which is the defining function of a clapper (check) valve. The other options describe devices or functions (venting, manual release, or a normally closed/only-on-demand mechanism) that do not capture the single-direction flow control of a clapper valve.