Why should dry barrel hydrants be opened completely?

The correct answer highlights the importance of fully opening dry barrel hydrants to ensure that the drain valve is fully closed. When a dry barrel hydrant is operated, it is designed to drain water from the barrel after use to prevent freezing in colder climates. If the hydrant is not opened completely, the drain valve may not seal properly, leading to residual water remaining in the hydrant, which can freeze and potentially cause damage or functionality issues.

In addition to preventing freezing, a fully opened hydrant allows for optimal water flow and helps to ensure that the internal mechanisms operate as intended. This is particularly important in emergency situations where quick access to water is critical. Understanding this operational characteristic is vital for effective hydrant use and maintenance within fire suppression activities.