What does water pump head mean? And the term maximum head?

What is "water pump head"? In simple terms it is the pressure that must be generated by a water pump to run the waterfall, fountain and other pond components.

Most water pumps used in ponds are those that have an impellor which rotates very quickly. The general term is centrifugal water pump because pressure is created by centrifugal force created by the rapidly spinning impellor. The speed of rotation is normally constant and in practice this means the amount of energy imparted to the water pumped out by the pump is also constant. In practice this constant amount of energy can be divided as follows ...

• Use the energy to pump more water volume to a lower head or

• use the energy to pump less water volume to a greater head

If you understand these two options you are well on the way to conquering any fear of deciding o any water pump specification. You can demonstrate this variable situation in practice very easily ...

Hozelock, Blagdon, OASE, Heissner products in UK

Best way to understand pump head.

Attach a pipe to your water pump say 9 feet long & observe what happens as follows ...

1. Assuming you are using a submersible water pump .... place the water pump in any kind of reservoir and hold the pipe at water surface level. You will see that quite a lot of water flows out of the pipe.

2. Now lift the pipe slowly and continuously and you will start to see that as pipe attached to the water pumps gets higher above the water surface that the flow of water from the pipe gets less and less

3. If the water pump you are testing this way is fairly small (ie low maximum head)  the water flow might even stop at say 6 feet

Head is another term for pressure

 Head developed by the water pump in practical terms in a pond situation simply means height to which the water is pumped. This height is more often than not the difference between POND SURFACE (not bottom of pond) and INLET TO WATERFALL ... notice the arrows on the right hand side of the sketch which show the head for this submersible pump which is pumping water to a 3 tier waterfall.

You must be able to determine the correct water pump head for your system in order to specify the correct water pump itself. What we now understand is that the higher the pump head for pond pumps to operate against then the lower is the amount of water pumped by any single water pump. This is because the pump has to generate more pressure and can only do this by reducing the water flow; in simple terms more flow equals less pressure or less pump head from the same water pump.

In addition to fully specify a pond water pump you need to know exactly what water pump flow is.

This relationship between pump head and water flow rate is a very important observation, which can be critical when selecting water pumps used to feed pond waterfalls.

Maximum Head and A Gentle Warning

The term maximum head is almost always supplied on the water pump box and it has been responsible for a large proportion of badly specified water pumps. In practical terms maximum head is almost meaningless because at maximum head the water flow from the pipe is ZERO ... the energy generated by the pump is all being used to just lift the water to the height required. No more energy is left to push any water flow.

A bit of a water pump complexity that can often (not always) be ignored

When water is pumped through a pipe with any kind of fittings (eg 'T' pieces, valves, in-line UV lights etc) then some of the energy generated by the water pump is lost in making the water flow through these restrictions.

To specify the total water pump head accurately for a pond system the pond pumps head loss (ie pressure loss) as water flows through pipes and fittings in the garden pond system shold be taken into account. This head loss is referred to as friction loss. For practical purposes in small ponds using short length of pipes and few bends and fittings this can be ignored if you do the following:

• Do not use pipe diameter of less than 25mm or 1”

• Do not use a length of pipe more than 3 metres (10ft) long

Ribbed hose pipe is by far the best pipe to use on a garden pond since it does not restrict pump flow when bent to form curves or bends often required in a pond set-up.

When in any doubt go for a larger pond pump than you think you need. However I think you would be better off to save this money by understanding your pond pump head as it relates to your own system. It is easily calculated using the FREE Excel program and you will save money.

Knowledge of water pump head will also give you great power when dealing with retailers who do not fully understand correct water pump specifications. Water pump head knowledge will almost certainly guarantee you discounts when buying pond pumps. It will also save you operating costs.

This important subject is covered in far more detail in my book. Understand this concept and you will save yourself a lot of money and hassle.

In order to fully specify a pond pump you need to know in addition to pond pump head exactly what pump flow is needed for your garden pond. This pump flow depends upon whether you have a waterfall or not, whether you have koi or goldfish or just plants in the pond.

Now you know how to calculate pond pump flow and pond pump head lets show you how to use a pump curve ... click here how to read a pond pump curve