When using a fire hydrant to flush wastewater lines, what is a crucial requirement?

Using a fire hydrant to flush wastewater lines requires a crucial safety measure: the installation of a backflow prevention device. This device is essential because it prevents the potential reverse flow of water, which can lead to contamination of the public water supply. During the flushing process, the pressure in the wastewater line may be higher or fluctuate, thus posing a risk of mixing wastewater with potable water if backflow occurs. The backflow prevention device acts as a safeguard, ensuring that dirty water does not contaminate the clean water system.

While other considerations, such as how quickly the hydrant is opened or closed, and whether internal controls are used, may also be important, they do not address the essential health and safety concern of contamination. Utilizing the hydrant without precautions, as suggested in one of the choices, would be highly negligent and contrary to best practices in water management and public health safety.