Which statement best describes the action of a check valve?

• A. It allows flow in one direction and prevents reverse flow.
• B. It increases system pressure.
• C. It vents gas to atmosphere.
• D. It regulates flow rate.

Answer: (A)

A check valve is a one-way gate in a line. It opens to allow flow when the fluid moves in the forward direction and automatically closes if flow tries to go backward, preventing reverse flow. This keeps pumps, tanks, and downstream equipment safe from backflow and potential damage. It doesn’t by itself raise system pressure, vent gas to the atmosphere, or regulate how much fluid flows; its purpose is simply to block reverse flow while permitting forward flow.