An atmospheric pressure vacuum breaker shall not be subjected to water pressure for more than how many hours?

The correct choice relates to the tolerance of an atmospheric pressure vacuum breaker, which is designed to prevent backflow and protect drinking water supplies. These devices are sensitive to prolonged exposure to water pressure because their function relies on creating a vacuum to prevent the backflow of contaminated water.

When subjected to water pressure for more than the specified duration, the vacuum breaker can be damaged or fail to operate as intended, compromising its effectiveness. Generally, the recommendations for maximum pressure exposure are designed to preserve the integrity of the device.

Limiting the pressure exposure to 12 hours allows for adequate periods of testing and maintenance without risking permanent damage to the vacuum breaker. Thus, it ensures that the device can continue to function properly in its essential role of protecting against contamination in the potable water supply.