Selecting
The Right Pump
Before you can pick the best pump for your pond, you need to determine what
flow rate
and total dynamic head (TDH) you want. Since the flow rate is affected by
the head it is working against, you must know both parameters to properly
select a pump.
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Flow –
The exact flow you will need depends on many factors including the size of
your
pond and waterfall as well as the amount of fish, plants and sunlight. In
general, most
ponds will operate nicely if you turn the water over approximately once an
hour to once
every three hours. This means if you have a 4000-gallon pond, you want about
4000 gallons per hour or 67 gallons per minute.
Head –
Head is a measure of resistance to flow. If a pump has a maximum output of
20 head feet, it means it can pump water 20' straight in the air. If a pump
is rated at 50
gallons per minute at 10 feet it means it can overcome 10 feet of head (TDH)
and still
deliver 50 GPM. As you increase the head, you decrease the flow rate. To
maximize
your flow, you must minimize your head. For pond applications the 3 main
sources of
head are:
Static Head –
This is the vertical distance you raise the water. To determine your static
head, measure from the surface of the pond (vertically), to the highest point
in the
discharge line where the water is discharged to the atmosphere. This is usually
the top of your biological filter, or waterfall.
Friction Head –
As water flows through pipe and fittings there is resistance. The
higher the flow and/or the smaller the pipe, the higher the resistance. Determine
your
overall pipe length, including equivalent length for your fittings. Consult
the friction
loss chart. Find where the column for your pipe diameter intersects the row
for your
flow rate & read the friction loss per 100 ft. pipe. Use large enough
pipe to minimize
friction loss. It is usually best to keep your friction loss (per 100 feet
of pipe) to less
than 6 feet.
Pressure Head –
Any additional pressure required by sand filters, spray nozzles, etc.
must be calculated. The conversion is 1 PSI = 2.31 head feet.
TDH –
To determine your TDH, add your static head, friction head and pressure head.
Now
that you know your flow and head, you can select a pump that provides this
performance, and does so
efficiently.
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We Hope this information have been helpful.
Please feel free to call of E~Mail us to help you pick the right pump for
your application.
bj@pondarama.com
717 532-7212
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