In what situation might a pressure differential not be sufficient for drafting?

The situation where a pressure differential might not be sufficient for drafting occurs when the water source is too deep.

When drafting water from a source such as a pond or river, the location and depth of the water can significantly impact the ability to create an adequate pressure differential needed to draw water into the pump. If the water source is too deep, the height of the water column can exceed the capabilities of the pump, making it difficult or impossible to achieve the necessary suction.

In essence, deeper water sources can result in increased weight and pressure that creates a challenge for the pump to lift water into the system, thereby hindering effective drafting. This situation highlights the importance of considering the physical conditions of the water source in relation to the capabilities of the firefighting equipment being used.

Other potential factors like using too many hoses, improperly using foam concentrate, or having clogged hoses can complicate flows and pressure, but they do not lower the pressure differential in the same way that depth does.