Pipe Flow Calculator
Calculate water flow velocity and discharge in gravity-fed pipe systems using the Hazen-Williams equation
Calculate Pipe Flow Properties
Internal diameter of the pipe
Total length of the pipe
Vertical drop from start to end of pipe
Material affects the roughness coefficient (C)
Flow Calculation Results
Hazen-Williams Formula: v = k × C × R^0.63 × S^0.54
Volume Flow Rate: Q = A × v
Note: Valid for water at 40-75°F (4-25°C) in gravity-fed systems
Flow Analysis
Example Calculation
Plastic Pipe Water Flow
Pipe Material: Plastic (C = 150)
Pipe Diameter: 0.5 ft (0.152 m)
Pipe Length: 12 ft (3.66 m)
Height Drop: 3 ft (0.91 m)
Unit System: Imperial
Step-by-Step Calculation
1. Radius: r = d/2 = 0.5/2 = 0.25 ft
2. Area: A = π × r² = π × 0.25² ≈ 0.1963 ft²
3. Perimeter: P = 2π × r = 2π × 0.25 ≈ 1.57 ft
4. Hydraulic Radius: R = A/P = 0.1963/1.57 ≈ 0.125 ft
5. Slope: S = drop/length = 3/12 = 0.25
6. Velocity: v = 1.318 × 150 × 0.125^0.63 × 0.25^0.54 ≈ 25.23 ft/s
7. Flow Rate: Q = A × v = 0.1963 × 25.23 ≈ 4.95 ft³/s
Pipe Material Roughness
Higher coefficients indicate smoother pipes with less friction
Flow Calculation Tips
Hazen-Williams equation is valid only for water flow
Accurate for temperatures between 40-75°F (4-25°C)
Gravity flow requires height difference between start and end
Higher pipe roughness reduces flow velocity
Larger diameter significantly increases flow rate
Understanding Pipe Flow Calculations
What is Gravity Flow?
Gravity flow occurs when water flows through a pipe due to gravitational force, without external energy sources like pumps. The flow depends on the elevation difference, pipe characteristics, and material properties.
Key Factors Affecting Flow
- •Pipe diameter (larger = higher flow rate)
- •Height drop (steeper slope = faster flow)
- •Pipe material roughness (smoother = less friction)
- •Pipe length (longer = more friction loss)
Hazen-Williams Equation
v = k × C × R^0.63 × S^0.54
- v: Flow velocity (m/s or ft/s)
- k: Conversion factor (0.849 metric, 1.318 imperial)
- C: Roughness coefficient (material dependent)
- R: Hydraulic radius (area/perimeter)
- S: Slope (height drop/pipe length)
Note: This equation is empirically derived specifically for water flow and is most accurate within the specified temperature range.