What Does 'Max Head' Mean?

Max Head refers to a pump’s capability to push water upwards (also known as ‘vertical lift’).  So for example, a pump which states ‘Max Head: 7m’ means the pump will be able to push water flow up to 7 metres high from the water surface.  What is often overlooked is that at 7 metres lift, the pump will deliver zero flow!

As water is pushed upwards through the hose, the output flow will gradually reduce so it’s very important to cater for any uphill lift to ensure that by the time the pump has pushed the water up to the top of the feature, there is still enough flow being delivered out of the hose.  

As a rough example, a pump which states a maximum flow rate of 12,000 Litres/Hour with a Max Head of 7 metres is likely to deliver half its flow when lifted half way up its max head figure (i.e. at 3.5 metres lift, you might expect the flow to reduce down to 6,000 litres).

Most good quality pumps are supplied with ‘performance curve’ charts which you are likely to find throughout our website.  These charts allow you to plot the expected flow once you know the expected vertical lift. If you are ever in doubt, do give us a call as we can correctly select the right pump for the task for you.

Another misconception when accounting for vertical lift (i.e. the height up to a stream or cascade) is that you may assume that the height is taken from the bottom of the pond or pool to the top of the stream.  However, a pump only needs to push water above the pool surface so you only need to measure from the water surface to the top of the stream. Therefore, it doesn’t matter if your pond is 30cm deep or 3 metres deep, as the measurement is always from the pond surface level.

Finally, always use the largest size hose that the pump will accept connection to.  If a small hose is used, this will drastically reduce the output flow of water, whether you are lifting uphill or not. There's a popular saying here at Water Garden - "You can't push Niagara Falls through a drinking straw".! 

For more details on pump hose selection and friction losses, view our 'What is Friction Loss? FAQ.