When performing branch line hydraulic calculations for the main piping, pressure due to elevation is added at a single point when:

When performing branch line hydraulic calculations for the main piping, adding pressure due to elevation at a single point is appropriate when the branch lines are installed on a slope or at different elevations. This is because variations in elevation directly affect the water pressure within the system.

In cases where branch lines are at different elevations, it is essential to consider the pressure changes that occur due to the effects of gravity. Specifically, water pressure increases by approximately 0.433 psi for each foot of elevation gained. Therefore, when calculating hydraulic demands or pressures within the system, it becomes necessary to adjust the pressure calculations to account for these elevation changes to ensure the system functions correctly across all branches.

This approach becomes critical in designs where branch lines may not be uniformly leveled, as failing to account for elevation differences can lead to inadequate water supply to certain parts of the system or overly high pressures that may risk damage or failure of components.