What action should be taken if the water tank level is decreasing during drafting?

When the water tank level is decreasing during drafting, opening the tank fill valve is the appropriate action to take. This action allows more water to enter the tank, which can help maintain a sufficient water supply for firefighting operations. If the tank fills while drafting, it indicates that there is a loss of water that needs to be compensated. By opening the fill valve, you're ensuring that the tank can replenish its water supply as you continue to draw from the draft source.

Other options might suggest alternative responses such as closing the tank fill valve or adjusting pump pressure, which would not address the immediate concern of dwindling water supplies during drafting. Checking hoses for leaks could also be a prudent course of action, but it would be a subsequent step rather than an immediate response to manage water levels effectively. The focus here should be on maintaining the flow and availability of water, and opening the tank fill valve directly supports that goal.