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Water Pumps
PROPER WATER PUMP SELECTION IS IMPORTANT!
Selecting a pump can be confusing, but it is critical that the
proper pump is chosen to ensure longevity and trouble free
performance. Following are several things to keep in mind when
selecting the right pump for your needs:
What is the volume of your
Pond?
To calculate the volume of your pond
multiply the length x the width x the depth x 7.481
Example: Pond 6' x 9' x 2' x 7.481 = approximately 807 US
Gallons Your pump should be able to process all the water in your pond at
least once every two hours at the minimum. In the
above example, your pond is 800 US gallons, you want at
least a 400 GPH (gallons per hour) pump.
How much volume do you
need for a Waterfall?
It takes approximately 36 gallons per minute to make a
waterfall that is 1' wide x 1" deep (1" deep water is considered an
average depth for residential applications.) The first step in
determining how much water you need is to multiply the width of the
waterfall in feet x 36 = gallons per minute needed to make 1" thick
water over your falls. Example: A 3"
wide waterfall would need 108 gallons per minute to be 1" thick.
This determines how much volume
you need Next, determine how much
head (or lift) there is from the surface of your pond to the top of
the waterfall. On a small simple waterfall the vertical lift
is all you need, however on large applications you also need to
factor in friction loss from the pipe as well as each fitting, to
get the total head.
This
determines head pressure Something
else to remember... If you are having a waterfall, you might
find it more pleasing to the eye to run another pump to your
waterfall as the pump discharge from your filter may not be enough
volume to be aesthetically pleasing. Don't exceed the filter
circulation to increase your waterfall appearance, as you will
affect the overall efficiency of your filter. Now that
we know water volume needed, and the head height it is needed at,
this
makes selecting a pump much easier. If you have a unique
application, are using an external pump or just want help, please do
not hesitate to call. Improper pump application is the leading
cause of pump failure - you should have the best pump for your
application. Knowing the application and selecting the correct
pump for the job will increase the overall performance of the
feature and decrease the frustration of the customer. BUT, you
must also take into consideration filter size. Once you have
selected a filter, check the circulation of that filter and match
your pump to it. Check the flow chart on the pump
you are considering. This should give you all the information
you need on volts / amps, flow rates, and other valuable information
when selecting a pump.
External pumps
Using an external pump raises
several questions regarding proper pump selection.
Self Priming - A self priming
pump can sit higher than the water level being pumped by a few feet
(depending on the model) and will displace the air in the suction to
prime itself.
Non Self Priming - These pumps
must either sit below the water level being pumped, or must have a
check valve installed at the end of the suction line to keep water
in the system after being primed the first time.
All external pumps are designed to PUSH water, not PULL it.
This means that the pump should sit as close to the pond as
possible!
Proper plumbing is important
Your pump can only perform as well as
your plumbing system allows it to! Very often pipe is used
that is too small and then you can't figure out why a larger pump
doesn't give you more water. Always size your plumbing for the
amount of water you are pumping, regardless of the outlet size of
the pump!
Maximum water flow for a pipe size of:
| 1" = 25 GPM |
2" = 90 GPM |
6" = 700 GPM |
| 1
1/4" = 45 GPM |
3" = 225 GPM |
8" = 1500 GPM |
| 1
1/2"
= GPM |
4" = 350 GPM |
10" = 2500 GPM |
If your pump delivers more water than your pipe
can handle, you will not get the pump's rated amount - you will get
the PIPE's rated amount! Example:
Frequently contractors use 3" flex pipe when installing a pump which
has a 3" discharge but pumps 295 GPM at 5' of head. Since 3"
of pipe can handle a maximum of 225 GPM the pump does not deliver
the amount of water it is capable of! Always size your pipe
for the amount of water being pumped. Fittings
can also reduce flow - 90° elbows should
be avoided if at all possible (use two 45°
elbows.)
Proper electrical supply is important
Inadequate power supply is one of the biggest
contributors to reduced pump service life, poor performance and
premature pump failure. Low voltage caused by undersized
wiring, having too many items running on the same line and not
double checking the voltage / amp draw once the pump is operating
are common mistakes that lead to problems. All pumps need a
certain amount of back pressure to operate correctly. Often
times a ball valve is needed on the outlet side of the pump to
create the needed back pressure. Without this back pressure
the impeller will pump more water than the motor is rated for,
creating high amp draw and excessive heat. This will lead to shortened motor life and premature failure. By closing the
valve a small amount, back pressure is increased and the mor
operates within its designed service factor.
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