External and submersible
Pumps are available in external and submersible models, and each of the pumps has whirling palms that pressurize the water and push it into a motion. Submersible pumps are easier to use than external, but more expensive. They are easy to install, they start without priming, and most importantly, they work quietly.
Before buying a pump for your waterfall, check its electric rating. Large waterfall request powerful pump, so it consumes more electrical energy. Choose a magnetic-driven pump, which use less energy than direct- driven. Usually, the most efficient pumps are the most expensive, but they can pay for themselves in energy saving.
The most important parameter when choosing pump is to buy it in the right size. Manufacturers rate electrical power in amps or watts, but the critical measure is the number of gallons of water it will pump per hour (gph) to a height, called the head. To properly choose the size of your pump first, you should calculate the capacity of water in the waterfall. Usually, the pump for waterfalls should be able to turn over the total volume of water in an hour.
If you doubt, buy a more powerful pump. You can reduce flow with a valve. Also, when buying a pump for waterfall; make sure its head or lift is well above the height you have projected for your waterfall.
Measuring Gallons per Hours (GPH)
As a pump lifts water to spillway in a vertical pipe, gravity gives resistance. As the height of the waterfall increases , the gph of a pump reduces.
The resistance created by horizontal 10 feet water flow is equivalent to 1 foot vertical rising water flow. For example, if your pump forces water 30 feet horizontally, that means as 3 feet vertically. Knowing this, will tell you, that the pump lifts the volume of water needed, to properly operate a waterfall with the planned height and distance from the pump. Usually, the manufacturers will tell how much water circulates at 1 foot . If the height of spillway is between two listed heights, estimate what you could expect. For example, if you need 300 gph lifted to 3 feet above the water, choose a pump at least 300 gph at 3 feet of head. That same pump may circulate at 200 gph at 6 feet of height.
Take measurement of height from the pump, not from the water’s surface. For proper flow figure 150 gph for each inch of spillway width. This provides a 0, 5-inch-thick sheet of water over the falls. Also you need to know how far the water will go horizontally in the pipeline.
Although variation can exist from rated gph, but not more than their rated gph. Buy a pump with greater gph than needed. It is easily to reduce by using valve on the pipeline or a restrictive clamp on the flexible tubing. It has the effect as lifting water higher in the line. Some pumps come with a flow valve regulator.