The primary factor affecting power requirements for pumps is

• A. Ambient temperature
• B. Elevation change
• C. Pipe friction losses
• D. Motor efficiency

Answer: (C)

Pumps must overcome the total head the system requires. That total head is the static lift plus friction losses in the piping (and any minor losses). The power a pump must deliver to move a given flow is proportional to hydraulic power, which depends on the flow and the head. In typical water distribution systems, friction losses in long runs of pipe dominate the head that must be overcome, and these losses increase with flow, pipe length, roughness, and diameter. So the friction losses essentially set the main power demand. Ambient temperature can slightly affect viscosity but doesn’t usually drive power needs, elevation change contributes to static head but is often a fixed component compared to friction losses, and motor efficiency affects how much electrical power is drawn for the same hydraulic output rather than changing the hydraulic requirement itself.