While taking into account the size of the pond, the most important factor to consider is what the pump does in the pond. Does it power a waterfall (requires more water)? Does it operate a fountainhead or statue (requires less water)? Sometimes a pump is used for re-circulation only, with no visible water movement (requires flow rate equal to 1/2 to twice the pond volume). In other words, the way the pump is to be used determines the size needed.
Waterfalls require the most water flow. To be visually effective, 100 to 200 gallons of water per hour per inch of waterfall width is needed. A waterfall twelve inches wide needs 1200 to 2400 gallons of water flow per hour. More is OK, but less flow means a dribbling falls.
The outlet height is determined by measuring the vertical lift from the pond surface to the height of the top spillway. Add to this one foot for every ten feet of of pipe coming from the pump (which is located as far as possible from the waterfall) to the top spillway. This total outlet height can be matched to the chart for each pump to choose the correct flow rate for your spillways. Be sure to maintain 100 to 200 gallons per inch of spillway at the total outlet height.
Volume is more desirable than pressure when hiding the flow of water into the top spillway. Avoid water that squirts from the end of a pipe, because that’s what it’ll look like. Hide the end of the pipe behind rocks or plants to make the flow less obvious. Install larger tubing than the actual outlet size (using adapters) to eliminate pressure while maintaining volume. Determine the length of tubing by measuring the depth of the pond, the distance from the pump that is at the opposite end from the falls, and to the top spillway.
A rough idea for electrical use can be calculated as follows:
Find the watts rating on the pump, the box the pump came in, or on our website information. The following formula is used:
Watts X 24 hrs. ÷ 1000 = kilowatt hours (kwh) / day. Multiply by number of days in a month to get monthly kwh used. Take this number and multiply by amount you pay per kwh (it’s on your electricity bill). Your result is the amount the pump will cost to operate per month. This is helpful while comparing one pump to another when deciding which to purchase. Generally energy-efficient pumps cost more up front, but less to operate per month.