What is the main function of a check valve in a water distribution system?

The main function of a check valve in a water distribution system is to prevent reverse flow. This device is designed to allow fluid to flow in one direction while automatically closing to stop any backflow that could occur due to changes in pressure or hydraulic conditions. By doing so, a check valve helps maintain system integrity, protects equipment from potential damage caused by backflow, and ensures that the water distribution system operates efficiently.

This function is particularly important in preventing contamination and maintaining water quality, as backflow can introduce unwanted substances into the main line. The correct answer highlights the primary role of the check valve in safeguarding the system from the risks associated with reverse fluid movement, which is essential for the effective operation of water distribution systems.