How To Select The Right Pond Pump From Manufacturer's Pump Curves
In previous articles we discussed maximum flow
and also maximum head and how they could easily
confuse and result in the selection of a completely inappropriate pond or
waterfall pump. It was also shown that as the height to which any volume of
water had to be pumped increased then the flow of water would decrease ...
because the need to split the fixed energy supplied by the pump's motor between
flow (mass of water) and the head to which it has to be lifted.
This can be compared to your carrying a bucket of water up a ladder. You
would need to expend energy but if you wanted to carry 2 buckets of water up the
same level you would need to use twice as much energy. Since a pump motor cannot
change the energy it must either change the flow or the height to which water
can be lifted.
Pump curves show the relationship between how high a pump can deliver and
the amount of water delivered at that height. Take a close look at the graphs
below ... Pump curves for two distinct ranges of pond pumps are shown below.
The left side of the graphs shows the pump head in metres and the bottom graph
axis show the amount of water indicated as "Q" and measured in lph or
litres per hour.
Notice how flow drops quickly as head increases
How To Read The Graph To Pick The Right PumpYou simply read from the intersecting point of the pump pumps curves the ideal
pump size or model for your system. Try to choose a point that is somewhere in
the middle of the pump range. Let me give an example using graph on right hand
side ... and always remember if you're not sure go for the next size up.
-
Head or height to which I need to pump = 2
metres
-
Q or volume of water I want to pump at this
height = 1500 lph
-
You'll see that only 2 pumps out of the 4
curves can do this .... the uppermost 2 curves and the lower of these only
just manages to perform at this duty and this ignores any pressure drop due
to pipe length or fittings in the pipe system. I therefore believe the only
pump that will effectively do the job required is that shown in the top
curve namely the Techno 4000. Theoretically this latter pump will deliver
1500 lph of water at a head of 2.4 metres.
-
Study this example until you're very clear on
how to use a pond pump curve to select the ideal pump for your filter or
waterfall.
When buying submersible pumps to use in garden goldfish or koi ponds consider these
items:
-
Long 3-core cable on the submersible pumps to
prevent unnecessary joining of cables. Do not buy water feature or aquarium
pumps for use in a pond. This type of pump generally is in a small box, has
a short and often only 2-core cable.
-
Good instructions and performance details are
supplied for the submersible pump box.
-
Compliance with the country's electrical certification standards for
submersible pumps.
-
Low power consumption (look for details of the wattage or at
least amps. Know how
to check the running cost and compare pumps from
different suppliers
-
Minimum of 2 years guarantee displayed openly.
The longer the guarantee the more you can be
assured that the pump you buy is
reliable.
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