What does a check valve do in a plumbing system?

A check valve is a crucial component in plumbing systems, primarily designed to ensure that water flows in a single direction. This is essential in preventing backflow, which can lead to contamination of the potable water supply or other serious plumbing issues. By allowing water to flow only in one direction and automatically closing if the flow reverses, a check valve effectively protects the system from potential damage and ensures proper functioning.

Understanding the role of a check valve is critical for maintaining water quality and system integrity. If water were allowed to flow in both directions, as implied by some other options, it could lead to significant problems such as leaks, reverse flow, or even flooding in certain situations. Similarly, while regulating water pressure and filtering debris are important functions in plumbing, these tasks are not performed by check valves. Instead, they are managed by pressure regulators and filtration systems, respectively. Thus, the primary function of a check valve is indeed to prevent water from flowing backward, making it a vital safety mechanism in plumbing systems.