Why should you never throttle the flow using the hydrant valve on a dry-barrel hydrant?

When using a dry-barrel hydrant, it is crucial to understand the role of the drain hole in the system. The drain hole is designed to release any residual water from the hydrant after it is closed, ensuring that it does not freeze in cold weather conditions. If the hydrant valve is throttled, or partially closed, while water is flowing, the pressure in the hydrant may drop, causing the drain hole to stay open longer than intended. This can lead to soil erosion or undercutting around the hydrant and potentially the sidewalk, compromising the stability of both structures. Properly functioning drainage is essential for maintaining the integrity of the hydrant and surrounding infrastructure. Hence, never throttling the flow using the hydrant valve helps prevent these issues, ensuring safe and effective hydrant operation.