What should the source pumper begin its initial operation at in a relay operation?

In a relay operation, the source pumper is responsible for maintaining adequate pressure to ensure water is delivered effectively throughout the operation. Starting at 175 psi is commonly recommended because it provides a balance between the need for sufficient pressure to overcome friction loss in long hose lays while also considering the pressure requirements of the receiving pumpers at the scene.

This pressure setting takes into account various factors, such as the distance the water needs to travel, elevation changes, and potential losses incurred during transit through hoses. A starting pressure of 175 psi is generally considered optimal to ensure that the system operates efficiently while minimizing the risk of pressure drops that could affect firefighting efforts.