1. What is a Water Pump Motor Horsepower Calculator?

Definition: This calculator estimates the required motor horsepower for a water pump based on flow rate, total head, and pump efficiency.

Purpose: It helps engineers, plumbers, and irrigation professionals properly size pump motors for various applications.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( HP \) — Horsepower required
• \( Q \) — Flow rate (gallons per minute)
• \( H \) — Total head (feet)
• \( \eta \) — Pump efficiency (decimal, 0-1)
• 8.34 — Weight of water (lbs/gallon)
• 3960 — Conversion factor (ft-lb/min to HP)

Explanation: The formula calculates the power needed to move water against gravity and system resistance.

3. Importance of Proper Horsepower Calculation

Details: Correct motor sizing ensures energy efficiency, prevents motor burnout, and maintains optimal pump performance.

4. Using the Calculator

Tips: Enter the flow rate in GPM, total head in feet, and pump efficiency (default 0.85 for 85%). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is total head in pumping systems?
A: Total head is the vertical distance plus friction losses that the pump must overcome, measured in feet.

Q2: What's a typical pump efficiency value?
A: Most centrifugal pumps operate at 70-90% efficiency (0.7-0.9), depending on design and conditions.

Q3: Should I round up the calculated horsepower?
A: Yes, motors should be sized 10-20% above calculated HP to handle startup loads and variations.

Q4: How do I find my system's total head?
A: Measure vertical lift and add friction losses from pipe length, fittings, and other components.

Q5: Does this account for motor efficiency?
A: No, this calculates hydraulic horsepower. For motor power input, divide by motor efficiency (typically 0.9).