Which statement best defines total dynamic head (TDH) in fire pump hydraulics?

• A. TDH is the atmospheric pressure.
• B. TDH is the friction losses only.
• C. TDH is the total pressure head the pump must overcome, equal to static head plus friction losses plus other hydraulic losses in the system.
• D. TDH is static head only.

Answer: (C)

Total dynamic head represents the total pressure the pump must overcome in the fire protection piping. It includes the static head—the elevation difference between the water source and the discharge point—plus all friction losses in the pipes and fittings, as well as any other hydraulic losses such as those from valves, elbows, reducers, and other flow restrictions. This sum determines the discharge pressure the pump must deliver at the chosen flow rate. Atmospheric pressure is not part of TDH, and TDH is not just static head or just friction losses; it’s the combination of static head, friction losses, and other hydraulic losses that the pump has to overcome.