The primary reason for using dry barrel fire hydrants is to:

The primary reason for using dry barrel fire hydrants is to:

• A. Allow Easy Maintenance Of The Hydrant
• B. Keep The Barrel From Rusting
• C. Minimum Water Hammer
• D. Keep The Hydrant From Freezing

Answer: (C)

Dry barrel hydrants are built so the water inside the hydrant drains away after the valve is closed. When you shut a hydrant, a rapid stoppage of flow can create a pressure surge known as water hammer. By draining the water from the barrel, there isn’t a full water column in the hydrant to slam shut, so the potential pressure spike is greatly reduced. That reduced surge is the main advantage this design provides, which is why it’s described as the primary reason for using dry barrel hydrants. (Note that freezing prevention is another beneficial effect, but the question’s focus is on limiting water hammer.)

Dry barrel hydrants are built so the water inside the hydrant drains away after the valve is closed. When you shut a hydrant, a rapid stoppage of flow can create a pressure surge known as water hammer. By draining the water from the barrel, there isn’t a full water column in the hydrant to slam shut, so the potential pressure spike is greatly reduced. That reduced surge is the main advantage this design provides, which is why it’s described as the primary reason for using dry barrel hydrants. (Note that freezing prevention is another beneficial effect, but the question’s focus is on limiting water hammer.)