What determines the layout of a discharge manifold in relay operations?

The layout of a discharge manifold in relay operations is primarily influenced by the number of attack pumpers being used. In relay operations, multiple pumpers work together to ensure a continuous flow of water to a distance where it's needed, often at a fire scene. The discharge manifold is designed to efficiently distribute water to these various pumpers to maximize their effectiveness.

When there are more attack pumpers, the discharge manifold must be configured to accommodate the additional hoses and flow requirements. This means the layout should ensure that each attack pumper receives an adequate supply of water without creating excessive pressure losses or flow restrictions. Therefore, the correct answer emphasizes how the configuration directly correlates with the number of active pumping units engaged in the operation.

Other factors, such as the amount of water available, the skill level of the operators, and the terrain of the area, may influence operational efficiency and safety, but they do not determine the fundamental layout of the discharge manifold as directly as the number of attack pumpers does.