1. What is the GPM Formula?

The GPM (Gallons Per Minute) formula calculates the flow rate of water through a pipe based on the pipe's cross-sectional area and the velocity of the water. It is commonly used in plumbing, irrigation, and hydraulic engineering.

2. How Does the Calculator Work?

The calculator uses the GPM formula:

Where:

• \( r \) — Pipe radius (inches)
• \( \pi \) — Mathematical constant (approximately 3.14159)
• velocity — Water velocity (feet per second)
• 0.408 — Conversion factor to get gallons per minute

Explanation: The formula calculates the cross-sectional area of the pipe, multiplies it by the velocity to get volume flow, and converts it to gallons per minute.

3. Importance of Flow Rate Calculation

Details: Accurate flow rate calculation is essential for designing efficient water systems, ensuring proper pipe sizing, maintaining adequate pressure, and optimizing system performance in various applications.

4. Using the Calculator

Tips: Enter pipe radius in inches and water velocity in feet per second. All values must be positive numbers for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: Why is the conversion factor 0.408?
A: The factor 0.408 converts cubic feet per second to gallons per minute, accounting for the relationship between these units.

Q2: What is a typical water velocity in pipes?
A: Typical water velocities range from 2-8 ft/s, with 5 ft/s being a common design value for many applications.

Q3: Does this formula work for all fluids?
A: This specific formula is designed for water. Other fluids would require adjustments for different densities and viscosities.

Q4: How does pipe material affect flow rate?
A: Pipe material affects friction loss, which can impact velocity and ultimately flow rate. This formula assumes ideal conditions without friction loss.

Q5: Can I use diameter instead of radius?
A: Yes, but you would need to adjust the formula: GPM = (π × (d/2)² × velocity) / 0.408, where d is the diameter.