What happens to water in a dry barrel hydrant?

In a dry barrel hydrant, water only enters the barrel when it is needed. This design is particularly beneficial in areas where freezing temperatures are a concern. When the hydrant is not in use, it remains empty, which prevents the water inside the barrel from freezing. When a fire department connects a hose and opens the valve, water flows into the hydrant from an underground supply line to provide the needed pressure and volume for firefighting efforts. This mechanism ensures that the hydrant is ready for use without the risk of ice forming inside the barrel, which could lead to malfunction during a fire emergency.

The other options do not accurately describe the operation of a dry barrel hydrant. A constant full state does not exist since the barrel only fills when activated, and continuous flow is not possible without an opened valve. Freezing is also prevented by design, making the idea that it freezes regardless of temperature incorrect.