Which valve is typically required for backflow prevention in plumbing systems?

The check valve is specifically designed to allow fluid to flow in one direction while preventing backflow in the opposite direction. In plumbing systems, backflow can pose significant risks, such as contamination of potable water supplies. The check valve effectively mitigates these risks by automatically closing when there is a reverse flow, thus safeguarding the integrity of the system. This is particularly important in applications where pressure differences can occur, ensuring that any potential contaminants are kept out of the clean water supply.

In contrast, other types of valves such as ball valves and gate valves are primarily used to stop or start the flow of water, but they do not offer backflow prevention features. A pressure relief valve is designed to release excess pressure within a system but does not prevent backflow or unintended reverse flow. Therefore, in the context of backflow prevention, the check valve is the appropriate choice for ensuring system safety and regulatory compliance.