🚰 Water Pump Sizing Calculator — Flow Rate & Head
Calculate required pump flow rate, total dynamic head, and power for irrigation, stock water, and farm water systems.
Quick answer: Flow (m³/h) = Area × Depth ÷ Hours. 50ha × 25mm ÷ 24h = 52 m³/h. Total head = Static lift + Friction + Pressure (30-50m for pivot). Power (kW) = (Flow × Head × 0.0027) ÷ Efficiency.
🚰 Calculate Pump Requirements
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Required Flow Rate (m³/h)
📐 How Pump Size Is Calculated
Flow (m³/h) = (Area × Depth) ÷ Hours
For stock: Flow = (Animals × L/day) ÷ Hours ÷ 1000
Power (kW) = (Flow × Head × 0.0027) ÷ 0.7 (efficiency)
- Determine required volume — per day or per application
- Divide by pumping hours — gives required flow rate
- Estimate total head — static lift + friction + pressure (add 30-50m for pivot)
- Calculate power — flow × head × constant ÷ efficiency
📊 Worked Example
50ha pivot, 25mm application in 24 hours. Head: 20m static + 10m friction + 30m pressure = 60m.
Flow = (50 × 25) ÷ 24 = 52 m³/h (14.5 L/s)
Power = (52 × 60 × 0.0027) ÷ 0.7 = 12.0 kW (16 hp)
Select 15-18.5 kW (20-25hp) pump motor for safety margin. Use 63mm or 75mm mainline to minimise friction losses.
❓ Frequently Asked Questions
Flow = Area × Depth ÷ Hours. Example: 50ha × 25mm ÷ 24h = 52 m³/h. Total head = Static lift + Friction loss + Operating pressure (30-50m for pivot).
Cattle: 50-100 L/day. Sheep: 10-15 L/day. Pump flow = (Animals × Daily need) ÷ Hours pumping. Example: 200 cattle × 80L ÷ 10h = 1,600 L/h (1.6 m³/h).
TDH = Static head + Friction loss + Operating pressure. Static: vertical lift. Friction: 5-15m per 100m of pipe. Use larger pipe to reduce friction.
Power (kW) = (Flow m³/h × Head m × 0.0027) ÷ Efficiency (0.6-0.75). Add 20% margin. 1 hp = 0.75 kW.