Pumping height explained
Each pump we sell has a chart showing maximum pumping height and litres per hour flow at different head or pumping heights.
The information below is intended explain these calculations.
Head is also known as the "No flow or zero flow height", "Lift" "shut off" etc, The point at which nothing comes out of a tube. It does not matter what size tube* is used, this height is the same. *The flow is however effected by the tube internal diameter.
Vertical lift
For a given pump, the higher water is pumped vertically - the lower the flow; at a some height the flow will be zero. The terms "head height" or "lift" are used to indicate this vertical height, measuring how high the water can be pumped for a particular application. Each pump has a published graph showing its flow rate at various heads. Waterfalls or streams have the added factor of friction loss created by the longer hose run required between the pump and the top of the waterfall or stream.
Static head Why is the height from the pump to the top of the water not counted in the head calculations?. It's called Static head. It does not count as pumping height because the water is already at the surface and does not have to be pumped there.
Maximum depth the pump can be located. depending on the pump there is a maximum depth that a pump will operate. The larger the pump the deeper it's suitable placement. Call us for help if you are planning a pump depth over 1.5m
In calculating tube friction, the entire tube length must be used.
Friction loss - for waterfall or stream use.
Pumping water through tubing adds resistance, so an allowance must be made for friction loss inside the tube. As a rule of thumb add 10cm of head for every 1 meter of horizontal tubing run. However as the size of the tubing has a significant bearing on frictional resistance, the use of an undersize tube will increase frictional losses.
An allowance for friction loss must be added to the vertical distance (in meters) measured from the surface of the pond, over which you will be pumping the water. The resulting sum will be the 'Total Head' that the pump will be required to lift the water. You should compare the flow rate that you require, to the flow rate that the pump provides at this specific head. Feel free to call us on 1800 607 388 if you need assistance calculating tube friction loss.
If you a looking to select the best water pump for your rainwater tank then you will see specifications like rated and maximum flow rates or head. What do they mean? What should you look for? Will the pump be adequate for your needs? The focus of this article will explore the question of rated and maximum “head” in water pressure pumps.When talking about how pumps work, or looking over pump specifications, you will come across maximum and rated “head” distance. If you don’t know much about water pumps, then you are probably just wanting to know how much pressure it can output and whether such is adequate for your needs. So, what is head? Why is it even mentioned when you just want water pressure!? Pump head is about water pressure your pump can handle, only vertically. If you were to attach pipes to your pump and extend them vertically upwards, how far can your pump pressurise water against gravity? This is important to know, especially since your water source and pump will likely be lower than its access points on your property. Intuitively, a pump that exerts more pressure should be able to pump water higher and therefore have a higher head. With a general understanding of “head” there is another term you may have heard about – total head. What is “total head”? It is important to understand that the height a pump can pressurise water to is also affected by how full your tank is. A pump will be able to pressure water higher when received from a fuller tank than one that is almost empty. “Total head” is therefore a much more useful figure which removes the height of water in your tank from the equation.Now we understand what pump “head” is, there are normally two figures listed for this in pump specifications: “Rated Head” and “Maximum Head.” How are we to understand these two different values? It is best to examine what it would mean for a pump to have a maximum head of 35 metres. This means that under ideal install conditions, the pump can pressurise water to this height. Surely, this would be suitable for most home owners. Perhaps it would suffice, but there are two missing questions that must be answered before going with such a pump. The first question is the actual water flow rate once pressured to the maximum height? The point at which it is zero pressure is generally considered the “maximum head”. This means your access points will need to be much lower than the maximum head or water just won’t flow from your taps. The second is that maximum head represents ideal install conditions. The pipes plumbed around your property and into your home often have bends in them, t-joins, small tubing, distances and the like. The pipework can impact upon the “maximum head” pressure, and this is where “rated head” is better to observe. The figure under “rated head” represents the ideal height you should consider its use for – most pumps will quite simply not deliver above their rated head. Finally, you will want to know what pressure you might expect at certain heights. This is where pump manufacturers often provide line charts mapping head to expected water flow. If you measure the height from the location of your pump to your highest water access point, then you should have a good idea of what pump you will need. To make it easier, most manufacturers recommend the number of taps a pump is good for. You should now be in a good position tell if one manufacturer is overstating, although most are generally adequate reflections if you take into consideration not all access points will be used at once, water saving taps and aerators or the like might be getting used.