What is the charging pressure for Engine 8 when supplying water to Engine 3?

The correct answer is based on the understanding of how to calculate the required pressure for a supply line when an engine is providing water to another engine. Specifically, "E8 DP = FL + 1/2 demand" refers to the formula used for determining the discharge pressure (DP) from Engine 8 when supplying water to Engine 3.

In firefighting operations, when water is supplied from one engine to another, you need to account for friction loss (FL) in the hose and any additional demand for pressure to meet the needs of the receiving engine. The term "1/2 demand" indicates that the calculation includes half of the flow demand from Engine 3, which is a common practice to ensure an adequate flow rate and pressure are maintained at the receiving engine.

Calculating discharge pressure in this way ensures that Engine 3 receives sufficient water flow and pressure for effective firefighting operations. It takes into consideration not only the distance the water travels and the corresponding friction losses in the hose but also the necessary pressure increase to account for the operational demands of the second engine being supplied. This understanding of supply calculations is crucial for maintaining efficient and safe operations during fire emergencies.