A high-service booster pump delivers 1,500 GPM against a Total Dynamic Head (TDH) of 180 feet. If pump efficiency is 82% (0.82) and motor efficiency is 91% (0.91), what is the required Motor Horsepower (MHP)?

Formula Used: MHP = [Flow (GPM) × TDH (ft)] ÷ [3,960 × Pump Eff × Motor Eff]

Step-by-Step Mathematical Derivation:

1. Calculate Water Horsepower (WHP): (1,500 × 180) ÷ 3,960 = 68.18 WHP.
2. Calculate Brake Horsepower (BHP): 68.18 ÷ 0.82 = 83.15 BHP.
3. Calculate Motor Horsepower (MHP): 83.15 ÷ 0.91 = 91.37 MHP (~91.4 MHP).

⚠️ Common Exam Trap: Remember the hierarchy: WHP < BHP < MHP. Water Horsepower is always the lowest number; Motor Horsepower is always the highest.