Which device is commonly used to prevent backflow and cross-connection in a potable water system?

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Backflow prevention is about stopping contaminated water from flowing back into the clean potable supply when system pressures change. A vacuum breaker does this by letting air into the line if downstream pressure drops, which breaks any siphon and creates an air gap. That air gap prevents water from being drawn back into the distribution system, effectively stopping backflow and reducing the risk of cross-connection with non-potable sources. This makes it a common, straightforward device for protecting potable water supplies, especially on outdoor outlets and irrigation lines. The other options don’t provide this anti-siphon function: a gate valve just shuts off flow, a strainer removes debris, and a pressure reducing valve lowers downstream pressure but doesn’t prevent backflow.