1. Pond Volume
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 at least once an hour. Use this calculator to determine your pond volume.
2. Waterfall Width
It is recommended between 100 - 200 gallons per hour (GPH) for every inch of waterfall width. On the lower flow rate (100 GPH) will give you a slower stream vs the higher flow rate (200 GPH) will give you a faster stream over your waterfall. Aquascape recommends 125 GPH for every inch of waterfall. Use this calculator to help you calculate your low and high flow rates.
3. Choose the higher of the two numbers calculated above in steps 1 and 2 (Pond Volume and Waterfall Flow Rate) to determine your "Recommended Flow Rate". From here, you need to calculate your head height.
Head height consists of:
Elevation: Height difference from water level in the feature to the top of the waterfall.
Pipe Length: Total length of pipe (10 feet of pipe = 1 foot of head height)
Fittings Used: 90 degree fittings (equate to 2 feet of head height) and all other fittings (1 foot of head height) contribute to head losses.
Use the calculator below.
4. Take your Recommended Flow Rate and your Head Height, both found in Step 3, and use this to determine the "Best Operating Zone" on the Pump Flow Chart. Below is an example
of a Pump Flow Chart. As an example, if you're Recommended Flow Rate was 3,500 GPH with 15' of Head Height, the best choice would be the 5-PL Pump because it is within the "Best
Operating Zone" shown in dark green with an "Application Head Height" in the range of 10' to 18'.
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