What is the purpose of a vacuum breaker?

A vacuum breaker plays a crucial role in maintaining the safety and integrity of water systems exposed to potential backflow conditions. Its primary purpose is to prevent backsiphonage, which can occur when there is a sudden drop in pressure within a water system. This drop can cause contaminated water from a surrounding source or an open container to be drawn into the clean water supply.

By allowing air to enter the system at a critical point, the vacuum breaker ensures that a negative pressure does not create a siphon effect that could draw pollutants into the potable water system. This is essential in maintaining water quality and public health, especially in situations where potential contaminants are present nearby, such as in irrigation systems, irrigation from a pond, or in areas where chemicals are stored.

Though the other options present valid functions relevant to plumbing and system design, they do not pertain directly to the specific function of a vacuum breaker. For example, allowing air into a system to manage pressure or regulating water flow during high demand is not the primary function of a vacuum breaker, nor is filtering contaminants from the water supply. The unique role of backsiphonage prevention distinctly aligns with the correct answer.