How to Calculate Waterfall Flow Rate
For waterfalls and streams, your waterfall flow rate should be at least 100 gallons per hour for every inch wide the waterfall is. For more noise and “white-water” from your falls, increase the waterfall flow rate to 200 gallons per hour per inch of waterfall width.
Waterfalls made of water falling off cut stone, 100 to 150 gallons per hour per inch wide of waterfall will work. Increase the waterfall flow rate towards 150 gph for more noise and white water.
For waterfalls made of water falling off jagged boulders, 150-300 gallons per hour per inch wide of waterfalls will create a nice waterfall effect. Increase the waterfall flow rate towards 300 gph for more noise and white water.
For waterfalls made of rounded boulders, 300-500 gallons per hour per inch wide of waterfall will create a nice waterfall effect. Increase the waterfall flow rate towards 500 gph for more noise and white water.
Next to each of our pumps will be a chart showing how many GPH (gallons per hour), GPM (gallons per minute) that pump will provide at 5′ of head, 10′ of head, etc. To understand this you need to remember that water is heavy at 8 pounds per gallon – and the higher a pump has to push the water the less volume it will provide. Important – the feet of head is the distance from the surface of the water level in the pond to the top of the waterfall.
To create a nice looking waterfall stream, it takes approximately 1,800 gallons per hour
(30 gpm) waterfall flow rate for every 1 foot of width.
To determine the GPH/GPM needed for your waterfall or stream – multiply the width in feet x 30 GPM.
Example: To build an “average” waterfall 3′ wide and 10′ high above the pond – multiply 3′ (width) x 30 GPM which equals 90 GPM or 5,400 GPH at 10 feet of head.
Now look through our pumps to find the pump that achieves 5,400 GPH/90 GPM at 10 of head. There’s your pump! Its that simple! You can double the flow rate to achieve a roaring cascade of “white-water” or scale down the flow rate for a more gentle effect.
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