What should a firefighter do after connecting a supply line to the hydrant?

After connecting a supply line to the hydrant, the firefighter should fully open the hydrant to ensure that adequate water flow is provided to the supply line. Fully opening the hydrant allows for the maximum volume of water to be delivered, which is crucial for firefighting operations. It also reduces the risk of creating air pockets in the line and ensures that the system is pressurized properly.

This procedure is vital as it establishes a reliable water source for the fire attack, enabling firefighters to effectively engage the fire with the necessary amount of water. Additionally, fully opening the hydrant helps to clear any debris or sediment that might have settled in the hydrant, ensuring clean, unobstructed water flow.

In circumstances where water flow is critical, such as in a fire situation, failing to fully open the hydrant could compromise the effectiveness of the firefighting efforts, making this step essential for effective operations.