Jed Rothwell wrote: > I looked at the video again. That is not a siphon, because the pipe > coming down is not full. There is plenty of air. The pump really is > pushing the water up 3 meters. As I said that takes ~120 W, judging > by fish-pond pumps, which are pretty efficient.
Indeed it seems it's not a siphon but it's hard to tell whether the pipe coming down is really empty, it could be obstructed close to the end to give that impression. But even if it really is pushing the water up 3 meters, as I said 120W for 9 GPM up 3m is only 17/120=14% efficient, as Horace and another commenter of the video confirmed. Also you seem inclined to believe that pump head could determine power consumption for a given efficiency, i.e. 3m -> 120W for a pretty efficient pump, irrespective of flow rate. As a counter example, see e.g. the pump below (a positive displacement type), it pumps water much higher (10m) and consumes only 4.5W, and it's not particularly efficient: its flow rate being 3L/h it lifts 3/3600 kg/s, i.e. every second it does a work against gravity of m*g*h=3/3600*9.81*10 = 0.08J. So its useful power is 0.08 J/s = 0.08W, i.e. its efficiency is only 0.08/4.5=1.8% http://www.aquatics-warehouse.co.uk/acatalog/aquarium_supplies_AQUAMEDIC_PUMPS_240.html Dosing Pump SP3000 The SP 3000 dosing pump is an economic peristaltic pump for pumping small volumes of water. It is used with all bypass filters like the Nitratreductor and the Calciumreactor, but also to top up evaporated water combined with an aquaniveau and the Kalkwasserreactor. A further application is the automatic dosing of fertilisers and minerals. In freshwater aquariums, the iron fertiliser ferreal can be added daily. In coral reef aquariums, the addition of calcium and trace elements (products of the Reef Life series) can be automated using the SP 3000. The pump is supplied a long life Santoprene, hose. technical data: SP 3000 capacity, fixed: 3 l/h (c. 0.8 gph) max head (pressure): (10 m, c. 30 ft) 1 bar, c. 14.5 psi Motor: Synchronous 20 rpm power consumption: 4.5 watts pump hose: Santoprene Michel
