Pumps and curves

When getting a clear picture on which pump is going to be best suited for you it is vital to understand your pump's curves!

Take a look at the chart below.

Pump Curves

This is a chart that illustrates the curves for 7 different pumps.

On the vertical axiz we can see the flow rates given by each pump. On the extreme left you can see the maximum flow rate of each pump - the D20000 model for instance will deliver 20 000 l/hr. The pump is rated at only 160W.

On the horizontal axis is the head expressed in metres. This tells us the maximum head each pump can pump vertically upwards into the air. The same D20000 intersects the axis at  just under 3m, call it 2.8m

In other words, what this is telling us is that if we used this pump to pump directly upwards into the air, the maximum vertical life the pump can achieve is 2.8m. If we had a transparent pipe 5m tall, you would see the water in the pipe rising up till 2.8m and then stopping.

Note, it makes no difference how thick this pipe is. If the pipe was 200mm in diameter, or 20mm in diameter the pump will not be able to life the water any higher than 2.8m.

Interesting huh? It might seem to make no sense intuitively, but that's physics for you.

When it comes to pumps, head is everything.


What you will find is that generally pumps that are more powerful in terms of watts consumed per litre per hour of water delievered are capable of pushing water to much greater heights.


For instance look at these curves. They are very different.

Speck pump curves

Here, head is on the left and flowrate on the horizonal axis. Still we can see instantly that even at 2m head the smallest Porpoise pump is pushing close on 16kl/hr. At 3m, when the D20000 would be moving zero water the Porpoise will barely have any appreciable drop in output.


So, what this data is telling you is that depending on your application, your pump may or may not be suitable. If you are only pumping up half a meter, it makes sense to use a pump using 160W as opposed to one deliverying slightly less water but using almost 3 times as much power to do so.

Conversely, if you have a system that has a higher head, you will need a more powerful pump.