What is the purpose of the drain hole in a dry barrel fire hydrant?

The purpose of the drain hole in a dry barrel fire hydrant is to remove water from the riser to prevent freezing. In colder climates, the water contained within the riser can freeze when temperatures drop. The drain hole is designed to allow any residual water to escape after the hydrant is shut off, ensuring that the riser remains dry during winter months. This functionality is crucial for maintaining the hydrant’s operability and ensuring that it is ready for use when needed, preventing potential failure during a fire emergency. By eliminating water that could freeze, the drain hole helps preserve the integrity and reliability of the fire hydrant system.