Pump Sizing Calculator

Pump Power Equation:

\[ HP = \frac{Q \times H \times SG}{3960 \times \eta} \]

Flow Rate (Q):

GPM

Head (H):

Specific Gravity (SG):

(1 for water)

Efficiency (η):

decimal (0-1)

Pump Horsepower (HP):

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1. What is the Pump Power Equation?

The pump power equation calculates the required horsepower for a pump based on flow rate, head, specific gravity, and pump efficiency. It's essential for selecting properly sized pumps in various industrial and commercial applications.

2. How Does the Calculator Work?

The calculator uses the pump power equation:

\[ HP = \frac{Q \times H \times SG}{3960 \times \eta} \]

Where:

\( Q \) — Flow rate in gallons per minute (GPM)
\( H \) — Total dynamic head in feet (ft)
\( SG \) — Specific gravity of the fluid (1 for water)
\( \eta \) — Pump efficiency as a decimal (0-1)
3960 — Conversion factor to get horsepower

Explanation: The equation calculates the theoretical power required to move a fluid at a given flow rate against a specific head, adjusted for fluid density and pump efficiency.

3. Importance of Proper Pump Sizing

Details: Correct pump sizing ensures energy efficiency, prevents premature wear, and ensures the pump can handle the required flow and pressure. Oversized pumps waste energy while undersized pumps can't meet system demands.

4. Using the Calculator

Tips: Enter flow rate in GPM, head in feet, specific gravity (1 for water), and pump efficiency as a decimal (e.g., 0.8 for 80% efficiency). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is specific gravity and when should I change it?
A: Specific gravity is the ratio of fluid density to water density. Use 1 for water, higher for denser fluids (e.g., brine), lower for lighter fluids (e.g., alcohol).

Q2: What is a typical pump efficiency value?
A: Centrifugal pumps typically range from 40-85% efficiency. Use manufacturer data when available, or estimate 70-80% for general calculations.

Q3: How does head relate to pressure?
A: Head (ft) = Pressure (psi) × 2.31 / SG. Total dynamic head includes static head, friction losses, and pressure requirements.

Q4: Should I add a safety factor to the calculated HP?
A: It's common practice to add 10-20% safety margin when selecting a pump to account for system variations and future needs.

Q5: What about motor sizing?
A: Motor HP should be equal to or greater than the calculated pump HP, considering service factor and starting torque requirements.