What is a check valve?

• A. Used to regulate temperature
• B. Used to drain water from the system
• C. Used to limit the flow in one direction
• D. Used to measure pressure

Answer: (C)

A check valve is a one-way valve that lets flow move in the forward direction but automatically blocks it if the flow would go backward. It uses a movable element (such as a disk or ball) that is pushed open by forward pressure and then seals to stop reverse flow when pressure reverses. This protects the system from backflow, keeps water from contaminating the source, and helps maintain proper pressure in the line. It isn’t used to regulate temperature, drain water, or measure pressure—that would be the job of other devices.