A pilot-operated check valve consists of a standard check valve design with a third port and ____________.

• A. Spool
• B. Adjustable knob
• C. Solenoid
• D. Piston

Answer: (D)

A pilot-operated check valve adds a pilot path that uses pressure from a third port to move a piston, which in turn unseats the main valve. The main valve acts like a regular check valve, blocking flow in one direction, but when pilot pressure arrives through the extra port, the piston receives that force and shifts the valve open so flow can pass. This arrangement lets you control when the valve opens, often at a lower cracking pressure or under remote control, instead of relying solely on the main flow pressure to pop the valve open. The piston is the actuator element that converts the pilot pressure into the movement needed to operate the check valve.