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 ...
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 ...
Best way to understand pump head.
Attach a pipe to your water pump say 9 feet long & observe what
happens as follows ...
-
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.
-
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
-
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:
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.
If you must have a smaller diameter pipe or a longer pipe run it is best
to get my free Excel computer program available when you buy my
book (see The Pond
Professor's practical water gardens website). This program will calculate the total pump head your system
requires very accurately.
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
Choose low cost reliable supplier on-line
I suggest you look a both suppliers and compare prices and shipping
costs ... take note that both suppliers offer specials at times and
these often appear in right hand border of this website.
These suppliers do sell other makes of pumps also of high quality and
performance which you might want to investigate and you can search the
websites for the model you want ...
Florida based
supplier specializing in very wide range of garden fish pond equipment
including pond pumps filters and UV lights ... just click the link
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