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Author Topic: Solar well pump?  (Read 2800 times)
Bottles
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« on: June 10, 2016, 09:27:02 PM »

Hi all,
In looking at setting up a solar pump to draw water from a shallow well to use in watering my garden. The well is a plastic pipe about 300mm (12in) in diameter with the water level 400mm below ground level with about 300mm of water.  There is fine sand at the bottom but also leaves etc as well. I've removed as much of the veg matter as  I can.
I would like to find a pump that can run of solar as it's about 75 meters to the nearest power supply. Lift the water a maximum of 3 metres to a water butt and use this for drip irrigation.
I've been using a drill driven pump so far that works after a fashion. As it's hard to prime and quickly drains the available  water in the well.
Though the well refills after about 15 min.
I was thinking of having a float switch in the water butt to control the pump. In the future I'm thinking of linking in more butts to water more parts of the garden.
How do you wire in the float switch and any recommendations on what pumps to look for?
Andrew
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billi
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« Reply #1 on: June 10, 2016, 10:58:54 PM »

boat bilge pump  with float witch  , perhaps , but may only work with a  battery involved ....





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Scruff
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« Reply #2 on: June 10, 2016, 11:39:34 PM »

Doesn't need to be a big battery with a relay driver.
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Bottles
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« Reply #3 on: June 11, 2016, 10:53:58 AM »

I'm not great on electricity. Relay would be the float switch? I'm thinking it might need two switches. On in the well so the pump doesn't run dry and one in the butt to control demand.
Is there a thread or link which explains how to match solar panels to pump size and size of battery? Or could what I'm looking at be available off the shelf?
Andrew
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knighty
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« Reply #4 on: June 11, 2016, 12:06:57 PM »

yes, one float in the water but and one in the well   (a lot of 12v boat pumps come with them built in, that might be easiest?)

to work out how many solar panels you need you need to decide which pump you want to buy first, so you can see how much power it uses

and to decide which pump you need you need to decide how much water you need...


if I was you I'd go for the smallest 12v pump you can find, that way it could pump slow and steady and (hopefully) not keep emptying the well and having to stop/start all the time?


you should get a non return valve too, so the hose pipe does not drain back into the well when the pump turns off :-)


EDIT: can't find a small enough bilge pump

THIS is the smallest 12v pump I can see, but it's only 3m lift so might be a bit tight for what you need... at 5 it's cheap enough to try?  - it'll fill your waterbutt in about an hour

THIS is the next smallest one I found, 4m lift, but it'll fill the waterbutt in about 20min, which might be too fast for the well ?

FLOAT SWITCHES just the first/cheapest ones I found, you could put one in the waterbutt and one in the well - if you put the one in the waterbutt upside down it'll work backwards


I picked cheap stuff because I figure you might as well go cheap first to try it out

and guess if you want to slow the pump down you can always add a small tap to the end of it to slow the flow... it's just not as efficient that way



p.s. first pump is 5ways, second is 15watts, so they both use naff all power and you'll get away with a single solar panel

at 12v - 5watts is about half an amp, 15 watts is about 1.2amps

so a normal car battery would power the pump for about 100hours or 45hours (ish) running constantly, even without the solar
« Last Edit: June 11, 2016, 12:20:21 PM by knighty » Logged
oliver90owner
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« Reply #5 on: June 11, 2016, 02:25:21 PM »

That first pump would be very slow.  Slow enough to not bother the replenishment rate quoted (although that may not be sustainable?)

That larger pump would likely not deliver as predicted above, either

These pumps are rated at maximum flow - ie zero head.  Flow at maximum head is, theoretically, zero but may take into account of a minimum flow to move away the heat generated in the pump head.

Some physics are needed to assess the true flow rate, along with a sensible 'pumping curve'.  There will also be pumping losses dependent on the length, bends and diameter of the delivery pipe.

There is no real problem in reducing a flow rate - increase the effective head or provide a bypass back to the reservoir.  To improve the obvious set up of pumping to the top of the butt only (water cascading from the pipe outlet), one could make the delivery pipe reach th bottom of the butt (the effective pumping height would be reduced for all but the full tank) but this would need a non return valve to avoid syphoning back to the well when the pump stops!
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farmer joe
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« Reply #6 on: June 11, 2016, 10:23:51 PM »

Hi if you are looking for the best efficiency without the bother of none return valves I have put a flexible pipe into the top of the tank, nearly twice round the inside and onto a small float so that the output from the pump is never more than 1 above the water level and yet has no risk of syphoning water back down the well. Hope this may be useful
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Bottles
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« Reply #7 on: June 12, 2016, 09:33:27 PM »

I have been looking at other pumps and was wondering if this one would be suitable?
http://www.ebay.co.uk/itm/282064233463?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

60watt motor, pump head 9ft and pumps 30liter per min.
I think this would be able to not drain the well to quickly.
Andrew
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knighty
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« Reply #8 on: June 13, 2016, 11:06:16 AM »

it's hard to know tbh.... but at 7.99 it's worth buying one just to give it a try :-)

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billi
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« Reply #9 on: June 13, 2016, 12:13:33 PM »

same ,  why not try  ..... but 60 watt is a lot for that pump , how  much water do you need for watering   per day ?
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« Reply #10 on: June 13, 2016, 12:39:07 PM »

Have a look at airlift pumps, they can  be used with small battery powered air pumps and don't mind running dry.  However they don't lift water very high so would have to be directly connected to the  trickle system.   
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