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Waterfall flow rate I sometimes get asked about waterfall flow ( how much water is required) so i thought it was about time to put fingers to buttons. As with all projects it is better and cheaper to put pencil to paper and decide what you would actually like. You should consider how wide you want your waterfall to be, it has to look in perspective with your pool say if you have a pool that has an edge of say 4 foot it would look a bit silly if the waterfall is 3 foot (we have seen it done) a rough guide would be to have it no more than half the width of the entry side. 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. Or to put it another way
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
Now that you have your figures, do not rush out and get the first pump you see, you must also take into consideration "head" that is to say the difference in height between the surface of the water (receiving pool) and the highest point, the pump you choose must be able to deliver the amount of water you require at the height of not just the waterfall but the height of the highest point of your waterfall. (For example you may wish to have a decorative outlet mounted on a wall as the start, if you do you must measure to the height of this outlet) Most pumps have on their box a diagram of flow rate to head height ratio, always go for the pump that is higher than you require since a larger pump can be turned down but a smaller pump can not be turned up. (if in doubt get the next one up, or for really wide waterfalls use two pumps, each with its own pipe) Please also remember that you need a high volume of water, not a fast flowing volume of water for a good waterfall. You should take into consideration that to achieve the required flow rate you should use the widest possible diameter pipe the pump you choose can support, (you can not put 20 people in a mini but you can put them in a bus) also it is better to use flexible pipe as you can put gentle curves in it rather than tight bends as these too will affect the flow rate. It is also true that the length of pipe and any other fittings i.e. ball valves will affect the flow, but for the "average" waterfall these figures are fine. Also if you are going to have a waterfall ideally you should run it using a separate pump, because if you have a biological filter, this will need to run 24/7 where as with a separate pump for your waterfall you can always switch it off when not required ( a good idea at night to save annoying the neighbours) if you need a pump may i suggest that you click here Why not email me and tell me what you have been doing or better still send a picture or two
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