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Waterfall calculation The "average" waterfall has water that is about 1/4 of an inch (6mm deep) flowing over the edge across its whole width, to calculate this you should be aware that for every one inch of width you should have a flow rate of 3.78 litres / minute. For the "average" waterfall you need: Imperial 100 gallons for every inch of water width every hour (average depth of 1/2 inch) which is 1.66 gallons / minute Metric 455 litres for every 2.5 cm of water width every hour (average depth of 12.5mm) which is 7.583 litres / minute Or if you want a water depth of 1/4 of an inch water depth divide the bold blue figures by 2 Or if you want 1/8th of an inch water depth divide the bold blue figures by 4 Not sure how many litres in a gallon? 1 gallon = 4.55 litres They are based on 4.5 litres / gallon example: 10 inch width 50 x 10 = 500 gph or 8.3 gpm 25 cm width 225 x 10 = 2250 lph or 37.5 lpm These figures do not take into consideration, any water loss due to friction, length of pipe run, etc. you should also use the biggest diameter pipe possible to avoid loss
Now you know how much water you have, you should also take into consideration how high (head) is the fall from the surface of the water, as your choice of pump needs to be able to cope with this too. For example you conclude your waterfall requires 100 gallons / hour, you buy a pump that delivers 100 gph and your waterfall does not work why? This is because in this case the 100 gph required is not being supplied at the top of your waterfall, all pumps have a flow rate graph, you should check will the required water flow rate be given at this height. When buying a pump from us, we check this for you. You should always use the biggest pipe possible to connect your pump to the top of your waterfall, as any restrictions will reduce this flow. Related links: Flow graph |
