Before initiating the lowering procedure of an aerial device, what should be done regarding the waterway system?

Before initiating the lowering procedure of an aerial device, draining the waterway system is crucial to ensure safety and functionality. This step removes any water from the system, preventing unintended pressure buildup and ensuring that the aerial device operates correctly during the lowering process. Water left within the system could cause it to remain heavier than intended, which can complicate the lowering and create a risk of malfunction. Additionally, draining the waterway system helps in avoiding potential damage that could be caused by the water's weight or any contaminants that may have accumulated within the lines.

Considering the other options, while closing valves, checking for leaks, and emptying the pump tank are important maintenance and safety practices, they do not specifically prevent complications during the lowering procedure, which makes draining the waterway system the most appropriate action.