What is the purpose of a check valve in plumbing?

A check valve serves the important purpose of controlling the direction of fluid flow within a plumbing system. It is designed to allow fluid to flow through it in one direction while preventing backflow in the opposite direction. This function is crucial in various plumbing applications; for instance, it helps maintain the efficiency and safety of systems such as water heaters, sump pumps, and irrigation systems.

When fluid moves in the intended direction, the check valve remains open. However, if there is a reversal in the fluid's direction, the valve closes automatically, preventing reverse flow. This not only protects equipment and fixtures from potential damage but also ensures that water pressure is maintained in the correct direction, contributing to the overall integrity and functionality of the plumbing system.

In contrast, other options highlight different functions that do not pertain to a check valve's primary role. While pressure relief, flow speed enhancement, and filtration are relevant processes in plumbing systems, they are accomplished using different types of valves and devices specifically designed for those purposes.