Why does a fire hydrant operating nut have a five-sided design?

A fire hydrant operating nut features a five-sided design primarily to prevent operation using a standard socket wrench. This design choice is intentional, as it limits access to specialized tools, ensuring that only designated personnel can operate the hydrant. The five-sided shape is less common than a standard hexagonal or square shape, making it harder for the average person to turn it with normal tools that are not specifically designed for that purpose.

By requiring specific tools, the design enhances the security and integrity of the fire hydrant system, ensuring that it is operated only in appropriate situations by trained individuals. This helps prevent tampering and unauthorized use, which could compromise the water supply or create unsafe conditions during emergencies.