What component feeds fuel to the drain?

• A. Ball valve
• B. Shut-off valve
• C. Spring loaded inlet check valve
• D. Needle valve

Answer: (C)

Feeding fuel to the drain relies on a device that allows flow in only one direction toward the drain while preventing any backflow toward the fuel source. A spring-loaded inlet check valve fits this role because it opens when the upstream pressure pushes fuel into the drain line and closes when pressure on the drain side tries to push fuel back or when flow stops. The spring ensures the valve stays shut when backflow is possible, keeping the fuel from returning to the pump or supply line.

This setup is ideal for purge or drain circuits in fuel systems, where you need a reliable one-way path to the drain without risking contamination or backflow. Ball valves or shut-off valves can block flow entirely but don’t inherently prevent reverse flow. A needle valve meters flow precisely but doesn’t provide a one-way check to stop backflow.