1. What is the Pump Size Formula?

The pump horsepower formula calculates the power required to move fluid through a system at a specified flow rate against a given head, accounting for fluid properties and pump efficiency.

2. How Does the Calculator Work?

The calculator uses the pump horsepower equation:

Where:

• \( HP \) — Required horsepower
• \( Q \) — Flow rate in gallons per minute (GPM)
• \( H \) — Total dynamic head in feet (ft)
• \( SG \) — Specific gravity of fluid (1 for water)
• \( \eta \) — Pump efficiency (decimal, 0-1)

Explanation: The formula converts the hydraulic power (flow × head) to mechanical power (horsepower) while accounting for fluid density and pump efficiency.

3. Importance of Pump Sizing

Details: Proper pump sizing ensures efficient operation, prevents motor overload, and reduces energy costs. Undersized pumps can't meet demand, while oversized pumps waste energy and may cause cavitation.

4. Using the Calculator

Tips: Enter flow rate in GPM, head in feet, specific gravity (1 for water), and pump efficiency (typically 0.7-0.9). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is total dynamic head?
A: The total height (pressure) the pump must overcome, including static head, friction loss, and pressure requirements.

Q2: What's a typical pump efficiency?
A: Centrifugal pumps typically range from 60-85% efficiency, while positive displacement pumps can reach 90%.

Q3: How does specific gravity affect pump size?
A: Denser fluids (higher SG) require more power to pump at the same flow rate and head.

Q4: Should I add a safety factor?
A: Yes, typically 10-20% additional horsepower is recommended for safety margins and future needs.

Q5: What about motor size?
A: The motor should be sized slightly larger than the calculated HP (next standard motor size up).