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Your pond pump is one of the most important elements of your pond. Not only does it provide oxygen to your fish, it circulates water throughout the system, aiding in filtration. The aesthetically pleasing sound of running water is a great aspect as well.
With all the responsibilities of a pump, proper pump sizing is important. It can be the difference between water flowing over your waterfall or barely trickling over it. Likewise, an oversized pump in a fountain can cause water to spew out of the fountain and onto the ground. Incorrectly sized pumps also can lead to premature pump failure and efficiency issues. So take some time to determine which pump best suites your needs.
There are several important factors to consider during your pump selection process:
In other words, how many gallons of water are in your pond? Gallons are figured by multiplying the average length (ft) x average width (Ft) x average depth (ft) x 7.5. There are differing opinions pertaining to recirculation values, but a good rule of thumb is to recirculate the entire volume of water once an hour. So, if you have a 5,000 gallon pond, then a 5,000 GPH pump is recommended.
Total Head Pressure
Total head pressure refers the combined friction losses sustained throughout the piping due to:
- Static Head or Vertical Lift- Vertical distance from the lowest water surface to highest discharge point measured in feet.
Friction Head- is the resistance to flow within all the components, such as piping, elbows, valves, etc. For example, some good rules-of-thumb friction head calculations are as follows:
- 10' of Hose = 1' head pressure
- 90° Fitting = 2' head
- All other fittings = 1' head each
The basic formula for determing Total Head Pressure is:
Static Head + (Length of tubing/10) + (# of 90° Fittings *2) + (# of Other Fittings) = Total Head
Example: In this example, the pond to be evaluated has a waterfall height (static head) of 10 ft, total tubing length of 20 ft, (3) 90° elbows and (1) gate valve.
Static Head = 10 ft
Friction Head =
- Total Tubing length = 20 ft = 20/10 = 2 ft of head
- (3) 90° Elbows = 3 x 2 = 6 ft of head
- (1) Gate Valve = 1 ft of head
Total Head = Static Head + Friction Head = 10 ft + 2 ft + 6 ft + 1 ft = 19 ft of Total Head
After you have calculated your total head (Static Head + Friction Head), it can be compared against pump performance charts, like the one shown below. These charts give pertinent information, including: maximum head height, flow rates at different head heights and other specifics to help aide in your decision. For example, Aquascape’s Tsurumi PL Series Pump Performance information is shown below for each model.
Always check the manufacturer’s specifications based on total head, as well as, the pond volume calculated above. Using the example above, if you need a 5,000 GPH pump based on pond volume, make sure that the pump provides that with the total head you have calculated.
Waterfall Weir Size
Waterfall weir size is yet another important factor in the pump selection process. It refers to how wide the spillway for the waterfall is. Aquascape recommends 1,000-3,000 GPH per foot of spillway width for residential ponds. For example, if your waterfall weir or spillway width is 2 feet wide, then a pump between 2,000-6,000 GPH should be ideal.
This information should give you a good understanding to help in your pump selection. Always refer to the manufacturer’s specifications to make your final decision.
The fish load in your pond is an equally important factor. Overstocked ponds lead to poor water quality and leave your fish susceptible to disease. Your fish need room to grow and a healthy environment is essential.
The rule of thumb for fish load:
- 33.33 gallons per inch of koi
- 20 gallons per inch of goldfish