The reading of a pressure gauge at the discharge of the pump, converted to feet (meters) of liquid, and referred to datum, plus the velocity head at the point of gauge attachment, is called

• A. Dynamic Head
• B. Discharge Pressure Head
• C. Static Head
• D. Total Discharge Head (hd)

Answer: (D)

The idea being tested is how pump discharge energy is expressed as head. In NFPA 20, head is energy per unit weight, so the total energy available at discharge combines all components: the elevation (static) head, the pressure head from the discharge gauge (converted to height of liquid), and the velocity head of the fluid at the discharge.

Reading the discharge gauge and converting it to a height gives the pressure head. Adding the velocity head at the gauge location accounts for the kinetic energy of the moving fluid. When you combine these, and include the elevation difference to the reference datum, you obtain the total discharge head, hd—the total energy available at the discharge.

That’s why the correct term is Total Discharge Head. The other options describe only part of the energy: a pressure-head reading alone misses velocity and elevation; static head is just elevation energy; dynamic head isn’t the standard NFPA 20 term for the full discharge energy.