What is the primary reason for using a dry-barrel fire hydrant?

The primary reason for using a dry-barrel fire hydrant is to keep the hydrant from freezing. In colder climates, the design of dry-barrel hydrants allows them to drain water that remains in the barrel when the hydrant is not in use. This drainage prevents any residual water within the hydrant from freezing, which can help maintain functionality during winter months. By ensuring that the water does not freeze, dry-barrel hydrants are reliable in the event of an emergency when fire suppression is required.

While increasing water flow, reducing maintenance costs, and enhancing visibility are all important factors related to fire hydrants, they are not the primary purpose of the dry-barrel design. It's essential for hydrants in regions subject to freezing temperatures to have mechanisms that prevent ice formation, thereby ensuring that they can reliably supply water when needed.