🌊 Water Guide
Water Flow Rate – Units, Formula and Conversion Guide
Everything about water flow rate — LPM, LPH, m³/hr, GPM units explained with conversion table, pipe velocity guide and pump flow rate reference.
What is Flow Rate?
Flow rate is the volume of water (or any fluid) that passes a point in a given time. In industrial settings, it determines pipe sizing, pump selection, tank fill time and cooling capacity.
Flow Rate Units Explained
| Unit | Full Name | Used For |
|---|
| LPM | Litres per Minute | Standard in Indian industry |
| LPH | Litres per Hour | Dosing pumps, slow flows |
| m³/hr | Cubic metres per hour | Pump datasheets, HVAC |
| GPM | US Gallons per Minute | Imported pumps, US specs |
| L/s | Litres per Second | Civil/municipal water |
| CFM | Cubic Feet per Minute | Compressed air, HVAC |
Flow Rate Conversion Table
LPM × 60 = LPH
LPM × 0.06 = m³/hr
LPM × 0.2642 = GPM (US)
LPM ÷ 60 = L/s
1 m³/hr = 16.667 LPM
1 GPM = 3.785 LPM
1 L/s = 60 LPM
Flow Rate Formula from Pipe Size
Q = v × A
Q = Flow rate (m³/s)
v = Velocity (m/s)
A = Pipe cross-section area = π × (D/2)²
Example: 100mm pipe, 2 m/s velocity
A = π × (0.05)² = 0.00785 m²
Q = 2 × 0.00785 = 0.01571 m³/s = 942 LPM
Recommended Flow Velocities
| Application | Recommended Velocity |
|---|
| Pump suction lines | 0.5 – 1.5 m/s |
| Pump discharge lines | 1.5 – 3.0 m/s |
| General water supply | 1.0 – 2.5 m/s |
| Fire fighting mains | 3.0 – 4.0 m/s |
Typical Industrial Flow Rates (Reference)
| Application | Typical Flow Rate |
|---|
| Small domestic pump | 15 – 30 LPM |
| Industrial process pump | 100 – 500 LPM |
| Cooling tower pump | 500 – 2000 LPM |
| Fire hydrant | 450 – 900 LPM |