Water Pump Horsepower Calculator

Water Pump Horsepower Formula:

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

Flow Rate (Q):

GPM

Total Head (H):

feet

Specific Gravity (SG):

(1 for water)

Pump Efficiency (η):

decimal (0-1)

Pump Horsepower (HP):

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1. What is Water Pump Horsepower?

Water pump horsepower (HP) is the power required to move a specific volume of fluid against a specific head (pressure) at a given efficiency. It's a crucial parameter for selecting and sizing pumps in various applications.

2. How Does the Calculator Work?

The calculator uses the water pump horsepower formula:

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

Where:

\( Q \) — Flow rate in gallons per minute (GPM)
\( H \) — Total head in feet
\( SG \) — Specific gravity of fluid (1 for water)
\( \eta \) — Pump efficiency (decimal, 0-1)
3960 — Conversion factor (foot-pounds per minute per horsepower)

Explanation: The formula calculates the theoretical power required to move the fluid, then divides by pump efficiency to get actual power required.

3. Importance of Pump HP Calculation

Details: Proper horsepower calculation ensures you select a pump that can handle your flow and head requirements without being oversized (wasting energy) or undersized (failing to meet demand).

4. Using the Calculator

Tips:

For water applications, specific gravity is 1
Typical pump efficiencies range from 0.5-0.9 (50-90%)
Total head includes both static head and friction losses
Always round up to nearest standard motor size

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between hydraulic HP and brake HP?
A: Hydraulic HP is the theoretical power needed to move the fluid. Brake HP is the actual power required at the pump shaft (includes efficiency losses).

Q2: How do I account for motor efficiency?
A: Divide the calculated HP by motor efficiency to get required input power (wire-to-water efficiency).

Q3: What's a typical pump efficiency value?
A: Centrifugal pumps typically range 50-85% efficiency, with higher efficiency in larger, well-designed pumps.

Q4: How does viscosity affect horsepower?
A: Higher viscosity fluids require more power. Use specific gravity of the actual fluid for accurate calculations.

Q5: Should I add a safety factor?
A: Yes, it's common to add 10-20% safety margin to the calculated HP to account for system variations.