WaterfallsThe other thing to bear in mind with a waterfall is the depth or thickness of the water you would like to run over it. Use the diagram below to work out how many gallons are needed to achieve a given depth of waterfall 0.3m (1 ft) across. If its wider, then multiply the flow in lph by the width in metres or multiply the flow in gph by the width in feet.
Also remember to measure how many feet your waterfall is above the surface of the pond. Now you have both gph and height you can use the performance tables, choose the pump with the performance curve closest to where two figures coincide.

Choosing the right pump for your pond...How many litres of water are there in your pond? Measure the widest, longest and deepest points of your pond in metres. then do this equation Width(m)xlength(m)xdepth(m)x1000= Litres. For example a pond1m deep,2.5m wide and 7m long would contain (0.9mx1.8mx6.3mx1000=10,206 litres) 10,206 litres. Alternatively in imperial measure Width(ft)xlength(ft)xdepth(ft)x6.23=Gallons. For example a pond 3ft deep,7ft wide and 20ft long would contain (3ftx6ftx21ftx6.23=2355gallons) 2355gallons.
To effectively filter a well stocked pond the pump needs to circulate its full capacity every two hours. A pond holding 10,206 litres would need a 10,206 litres per hour (lph) pump. Alternatively a pond holding 2355gallons would need a 1178 gallons per hour (gph) pump. I f you also want a waterfall with a drop of 4metres to the pond surface, the flow rate required would be 10,206lph at 4m head. In short you will need a more poweful pump.
