Step 1
Understand Flow Rate
Flow rate measures how much water a pump delivers, usually in litres per minute (L/min). Higher flow means more water delivered in less time.
Flow & Head Explained
Understanding flow rate and pumping head is the key to choosing the right solar water pump for your property.
Water source
Bore, dam, tank or creek. Your source shapes the setup.
Total head / lift
The total height the water needs to be pumped.
Flow rate
How much water you need per minute or per day.
Solar only or hybrid
Run on solar alone, or add AC/DC backup.
UNDERSTANDING PUMP PERFORMANCE
Why Flow & Head Matter
Flow rate and total head determine how much water your solar pump can deliver. As the height and resistance increase, water output generally decreases. Understanding these two measurements helps you select the right pump for your bore, tank, irrigation or livestock watering setup.
L/min
Flow rate
Metres
Total head
TDH
Pump sizing
THE BASICS
How Flow & Head Work Together
Before choosing a solar pump, it's important to understand how flow rate and total head affect water delivery. These two measurements determine which pump is suitable for your application.
Step 2
Understand Total Head
Head is measured in metres and represents the total resistance the pump must overcome, including vertical lift, pipe friction and any required outlet pressure.
Step 3
Match Flow to Head
Every pump has a performance curve showing how much water it can deliver at different head levels. Use this to find a pump that meets your required flow at your actual pumping head.
Quick guide
How Head Affects Flow
As the total pumping head increases, the flow rate generally decreases. This is why it's important to select a pump based on its performance at your required head, rather than its maximum flow rating.
Here's a real example using our Nomad 1.5-110 solar bore pump.
| Total Head | Expected Flow Rate |
|---|---|
| 10 m | 24 L/min |
| 30 m | 23 L/min |
| 50 m | 21 L/min |
| 70 m | 20 L/min |
| 90 m | 17 L/min |
| 110 m | 0 L/min |
Typical ranges only.
FAQ
Frequently asked questions
Quick answers about flow vs head calculations.
What's the difference between flow rate and head?
Flow rate is the amount of water a pump delivers, usually measured in litres per minute (L/min). Head is the total height and resistance the pump must overcome, measured in metres. Both are important when selecting a solar pump.
How do I calculate the total head for my solar pump?
Total Dynamic Head (TDH) includes the vertical height from the pumping water level to the delivery point, friction losses through pipes and fittings, and any required outlet pressure. Longer pipelines and smaller pipe diameters generally increase friction losses.
Does a longer pipe reduce water flow?
Yes. Water travelling through a pipeline experiences friction, which increases with distance and flow rate. Using a larger diameter pipe can significantly reduce these losses and help maintain better pump performance.
Why does my pump deliver less water at higher head?
As the pumping head increases, the pump must work against greater resistance, reducing the amount of water it can deliver. Every Outback Solar Pump has a performance curve showing expected flow rates at different head levels to help you choose the right model.
Need Help Calculating Your Flow & Head?
Not sure how much water you need or how to calculate total pumping head? Our Australian team can help you choose the right solar pump for your property.