The proper pump is the heartbeat
of an effective pond system!
Before you can pick the best pump for your pond, you need to determine what
flow rate and total dynamic head (TDH) you need. Since the flow rate is
reduced by the head it is working against, you must know both of these parameters
as well as others to
properly select a pump
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. This means if you have a 4000 gallon pond, you
want about 4000 gallons per hour, or 67 gallons per minute.
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, and increase your operating costs. To maximize your flow, you must minimize your
head, which also minimizes your operating costs. 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, fountain, 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 adding in
length for your fittings. Consult the friction loss chart. Find where the
column for your pipe diameter intersects the row for your flow rate and
read the friction loss per 100' 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. In other words, once you know the desired
flow rate, pick a pipe diameter, or schedule, that will give you less
than 6 feet of friction loss per 100 feet of pipe.
- Friction Loss - THIS CHART GIVES FRICTION LOSSES FOR YOUR GIVEN FLOW RATE PER 100 FEET OF
PIPE: EXAMPLE; IF YOU WANT 60 GALLONS PER MINUTE, AND YOU'RE USING 2 INCH
SCHEDULE 80 PIPE, AND YOU HAVE A 160 FEET OF PIPE, YOUR FRICTION LOSS IS 8.12 x
1.6 = 12.99 FEET OF HEAD. So we would either want to use schedule 40 pipe, or go
to 3" schedule 80 pipe.
- Fittings Loss - Now go to the bottom of the Friction Loss
page and pick out the number and type of fittings you are using
(use the worst case scenario if you have a bypass): Example; a
2" 90° elbow is the equivalent of an extra 6 feet of 2"
pipe, so if you have ten 2" 90° elbows you would add 60 feet
to your pipe length. After adding the extra feet for all your
fittings you recalculate your total feet of head. In this case it
would add 60 feet to 160 feet for a total of 220 feet or 2.2 x
8.12 = 17.9 feet of head.
- Pressure Head - Any additional pressure required by sand filters,
spray nozzles, etc. must be calculated. The conversion is 1 PSI = 2.31
- If our sand filter runs at 10 PSI, that would add 23.1
feet of head to the 17.9 feet required to overcome the friction
loss of our pipe and fittings. So now the total pump head is 41
feet without considering the static head. (Notice that the pump head
will increase as the sand filter gets dirty and increases the back
- Total dynamic head ( TDH) - Add your static head, friction
loss head, fittings loss head, and pressure
Type of head
||10' - above surface of water
||8.12' per 100 feet of pipe
||6' per elbow
||10 2" 90° elbows = 60 ft
||running at 10 psi x 2.31
Total Pump head in feet
- Don't forget to add up the equivalent feet of
pipe for all the fittings.
- Now that you know your flow and head, you can select a pump that
provides this performance, and does so efficiently.
- Performance Curves
Now we know that we need a pump that can handle 67 gallons per minute
at 51 feet of head. This information can be found on the performance
curves for the pumps.
We want to select a pump that has these results inside of the maximum
efficiency curve area.
If we have more than one pump that meets all these requirements we can
then select the pump with the lowest operating cost, i.e., lowest amps or
- Remember, a 230 volt motor will run at half the amperage of a
115 volt motor, but wattage is the amps times the voltage, so we have
not gained any cost savings because we doubled the voltage.
- A 2 horsepower motor can cost $2,000 per year to operate.
We also want a pump that is quiet enough to allow us to enjoy our pond.
Most manufacturers can supply a noise number in decibels (dB) at 3 feet from
the pump. We want the lowest dB possible. We can also mount the motor on
rubber noise isolation pads, or shield it with noise attenuating