What is the name of the smallest water main that supplies water to users and hydrants?

The correct answer is 'Service Lines.' Service lines are the smallest water mains within the water distribution system. They are specifically designed to deliver water from the water main to individual consumers, including residential and commercial properties, as well as to fire hydrants.

Service lines function as the final connection in the water distribution network, providing the necessary link between the larger mains and the end users. Their smaller size compared to primary and secondary feeders allows for accommodation of the water pressure and flow needed for domestic use and fire suppression.

Understanding the hierarchy in water distribution systems is crucial for firefighters and emergency responders as it helps in knowing where the connections to the water supply might be located, which is essential in firefighting operations.