Horsepower To Pump Water Calculator

Horsepower Formula:

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

Flow Rate (Q):

gpm

Head (H):

Specific Gravity (SG):

(unitless)

Efficiency (η):

(decimal)

Horsepower (HP):

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1. What is the Horsepower Formula?

The horsepower formula calculates the power required to pump water based on flow rate, head, specific gravity, and pump efficiency. It's essential for selecting the right pump motor size for water systems.

2. How Does the Calculator Work?

The calculator uses the horsepower formula:

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

Where:

\( Q \) — Flow rate in gallons per minute (gpm)
\( H \) — Total dynamic head in feet (ft)
\( SG \) — Specific gravity (unitless, 1.0 for water)
\( \eta \) — Pump efficiency (decimal, 0-1)
3960 — Conversion constant

Explanation: The formula calculates the theoretical horsepower required to move water, accounting for the fluid properties and pump efficiency.

3. Importance of Horsepower Calculation

Details: Accurate horsepower calculation is crucial for proper pump selection, energy efficiency, and preventing motor overload in water pumping systems.

4. Using the Calculator

Tips: Enter flow rate in gpm, head in feet, specific gravity (1.0 for water), and pump efficiency as a decimal (e.g., 0.8 for 80%). 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 1.0 for water, but adjust for other fluids like brine (SG > 1) or gasoline (SG < 1).

Q2: What is a typical pump efficiency value?
A: Pump efficiency typically ranges from 0.5 to 0.85 (50-85%). Centrifugal pumps usually have 60-80% efficiency at their best efficiency point.

Q3: Why is the conversion constant 3960?
A: The constant 3960 combines unit conversions: 1 horsepower = 550 ft-lb/sec, 1 gallon of water = 8.34 lb, and 1 minute = 60 seconds.

Q4: Should I add a safety factor to the calculated horsepower?
A: Yes, it's common practice to add a 10-20% safety margin to account for system losses, voltage variations, and future capacity needs.

Q5: How does head affect horsepower requirements?
A: Horsepower is directly proportional to head - doubling the head doubles the horsepower requirement, assuming other factors remain constant.