What keeps a check valve open in a piping system?

In a piping system, the operation of a check valve primarily relies on pressure in the line. The check valve is designed to allow fluid to flow in one direction while preventing backflow. The disc mechanism within the valve is kept open by the pressure of the fluid flowing through the pipe. When the fluid pressure is sufficient, it pushes the disc away from the seat allowing the flow to pass through the valve.

When fluid stops flowing or flows in the reverse direction, the pressure in the line decreases, causing the disc to return to its seated position and close off the flow, thus preventing backflow. This automatic response to pressure changes is what defines the functionality of a check valve in a piping system.

Other options, like gravity, weight of the disc, or manual operation, do not dictate the operation of a check valve. Gravity may play a role in specific valve designs, but it is not the primary factor in all instances. Manual operation is not typical for check valves, which are intended to operate automatically based on fluid flow.