What is the lowest operating temperature for a vacuum breaker?

Vacuum BreakersA vacuum breaker is an anti-siphoning check valve used in a variety of applications to prevent a vacuum from developing. When the vacuum breaker valve is sealed, its spring seats a ball against an O-ring. The low temperature limiting factor is the O-ring pliability. Although the vacuum breaker is rated to -70°F (-57°C), the durometer will steadily increase as the temperature drops so it may not form a perfect seal at -70°F (-57°C). In this low temperature environment, there also would be a need to make some provision to avoid frost formation on the sealing surfaces as well as in the flow passage. If there is moisture on the pressurized side and the temperature is below the freezing point, the internal components could become locked in place by frost thereby preventing the vacuum breaker from opening. While very low temperatures are suitable for vacuum breaker operation, care must be given to ensure frost does not impair the operation of the vacuum breaker.