Short and fast versus long and slow pumping?

peterthepainterpeterthepainter Registered Users Posts: 3
We have inherited a system which pumps water from a deep well using a powerful pump (sorry no details available at present). We have a huge tank to store the pumped water ready for use. The idea, according to previous owner, was to switch the pump on 3-4 times a day for a few minutes, whereupon the available water in the well would run dry and we have to wait for it to slowly replenish itself. The powerful pump, it would seem, is putting excessive strain on our limited solar electrics too.
This seems all wrong to me. Does it not make more sense to pump very slowly (using minimal power) for a long period? perhaps constantly during the day? Hopefully the well would never dry using this method.
Any thoughts on why one system is better than the other appreciated. Thanks.


  • mike95490mike95490 Solar Expert Posts: 7,505 ✭✭✭✭
    This would be a job for Grundfos SQL Flex pumps
     They run off solar panels, and will fill the tank in daylight, but not in cloudy or dark weather.     it's not good for a well or the pump, to suck it dry and then wait for recharge, a slower withdraw rate has always seemed better, but I don't sell big well pumps either !

    SQL Flex pumps are expensive, with their control box and some PV panels, but you don't need a big honking inverter and battery bank for them.

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  • jonrjonr Solar Expert Posts: 915 ✭✭✭✭
    Would be far less expensive to use a 24VDC submersible well pump.  Or possibly a lower power version of your current pump.
  • MichaelKMichaelK Registered Users Posts: 72 ✭✭
    A neighbor up the road from us has exactly the same problem.  What's happening is referred to as the well's "refresh rate".  That is, the rate in gallons per minute that water enters the bore hole.  So, it you have a well bore with a refresh rate of say 2.5 gallons per minute, and a pump that removes water at say 5.0 gallons per minute, the well will run dry.  At least for a while

    The big problem with this is a lot of submersable pumps are damaged running dry.  They are typically wired with a dry "shut off" switch that's positioned directly above the well, so when the water level drops down to the pump it will shut off. That is of course till the switch malfunctions and does not switch off in time to keep the pump from being destroyed.

    Does the well driller have a logo/placard on your water tank?  The original driller (or maybe your county records office) will have data concerning the bore's refresh rate.  That info will help you rationally decide what size pump is "supposed" be to there.  My guess would be somebody down the road replaced a worn out pump with a bigger model, not taking into account the low refresh rate.
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