What is the purpose of an atmospheric vacuum breaker?

An atmospheric vacuum breaker is designed primarily to allow air to enter a system during siphoning, which is crucial for preventing negative pressure that could lead to backflow or system collapse. When there is a drop in pressure in a piping system (for instance, when water is siphoned out), the atmospheric vacuum breaker opens to allow air to break the vacuum. This mechanism helps to stop the formation of a siphon that could otherwise pull contaminated water back into the potable water supply.

While preventing contamination from backflow is important, this is more directly handled by backflow preventers or other similar devices, not specifically by an atmospheric vacuum breaker. Maintaining pressure in a closed system and controlling water flow rate are functions typically associated with other types of devices like pressure regulators or flow control valves rather than an atmospheric vacuum breaker.