Selecting a pump involves a couple
of easy steps:
1)
Determine the MAX HEAD in feet (the height to rise above the
waterline)
2) Determine
the FLOW RATE in GPM (gallons per minute)
Multiply width of the stream, or if you have no stream the
width of the waterfall spillway outlet
(in feet) x 36* GPM = flow needed in GPM.
*36 GPM is a fixed number that you always use.
Example:
Step 1 - Let's
say your pump inlet is 2 feet below the waterline in
your skimmer. Let's say the top of your waterfall where
the water comes out is 6 feet higher than your pond level.
You measure your Max Head from the waterline and not
how deep your pump inlet is.
Your Max Head (how
high to lift the water) is 6 feet
You can see from the
Pump Comparison Chart
that a 6 foot lift is within limits
under the Max Head column
for any pump on this page.
Step 2
- Now we
need to find the right GPM flow rate. Let's say your
waterfall outlet opening is 24 inches wide, or 2 feet,
and you have no stream.
Multiply 2 times 36 GPM and you get 72 GPM.
Your flow rate is 72
GPM (gallons per minute)
or
Your flow rate is 4,320 GPH (gallons per hour)
Look at the
Flow Rates @ Feet of Head columns
and notice there are values from 5' to 30'
and since your water has to rise 6' feet
you can't use the 5' column so just move up to the 10'
column of values. Important: Always move up to the next higher
column and
never lower!
Now scroll
down that column looking for a pump that provides the
GPM you determined you needed which was at least 72 GPM.
The first one that fits your need is the EP6700 with a
flow rate of 80 GPM at 10' of head.
If multiple pumps fit your application you can compare
the cost to operate, outlet size, etc. to finalize your
selection. The worse thing you can do is get a pump too
small to properly turn over your water fast enough to
keep it well aerated and your biological filters working
the way that they should. Important: You can always reduce your
water flow if it is too fast with a valve, but you can never increase
it to make your pond healthier!
This
example will also support a stream from your waterfall
no more than 2 feet wide. If you have a stream wider
than 2 feet you need to increase your GPM. The length of
the stream is not a factor. All that matters is how high
the water needs to be lifted.
The
minimum GPM flow per hour for an Eco Pond is
1.5 times the total gallons per hour. In this case,
(4,320/150) x 100 = 2,880 Gallons So if your ponds
total gallons is 2,880 or less you are OK.
Reducing the flow rate of your pump: If
you start your pump up and you find your flow
rate is too much, you can always install an adjustable
flow valve on the
output line of the pump plumbing to reduce the flow rate
to where you want it. This will not hurt the pump at all
and will also save on energy costs. The backpressure
from this valve will reduce your energy costs and not
hurt the pump in any way or void the warranty. If you
install a pump too small and your flow rate is to low there is nothing you can do to improve it
except to buy a bigger pump.
