What is one function of a vacuum breaker?

The function of a vacuum breaker is primarily to allow for backflow prevention. This device is designed to prevent the backflow of contaminated water into the potable water supply. When a drop in pressure occurs in the plumbing system, the vacuum breaker opens to allow air into the system, breaking any potential vacuum that could draw water back into the supply lines. This is crucial in protecting the drinking water from contamination that could result from backflow incidents caused by changes in water pressure.

The other options do not accurately describe the function of a vacuum breaker. Increasing water pressure is not within its capabilities, as it does not enhance system pressure. Connecting multiple pipes is typically the function of fittings and connectors, not a vacuum breaker. Regulating flow rate is managed by different devices and technologies, such as flow regulators or valves, rather than a vacuum breaker.