After researching many solutions to an off grid water pumping solution, I researched many remote off grid blogs and video to come up with a solution.
The main goals I had were to eliminate any weak links in the system. The weakest point of the entire system eventually is the battery usually a lead acid type, that most of the solutions called for. These batteries being out in the sun, and the snow are taken to their limits which causes them to have a lifespan of about 2-3 years or less.
Since the cost of solar has decreased and is now around $1.20/watt by the time you add in shipping costs, I decided to oversize the panel output to compensate for the water pump’s minimum required voltage and amperage. Once I knew these figures, I searched for solar panels online on Amazon.com using our Amazon Prime membership that pays for shipping on select products. The goal was to find a panel that, at 15% of maximum output, was equal to the power requirements of the pump. Theoretically allowing the pump to run in full sun or overcast conditions and throughout the winter. The lower cistern is connected via a 3/4″ pex line to the main upper cistern. The upper cistern will have a float switch that says, hey if it’s sunny AND I’m low, it will close a switch that will activate a relay near the lower pump, that calls for 12v from the solar panels. This will then allow up-to 4-5 hours of pumping per day, at about 1.3 gallons per hour uphill about 400 feet and at a head of about 23′. The pump is capable of 50PSI, so you’ll see below how I came up with our requirements
What Pump Do I Need?
Our goals were 1 Gallon per minute or greater, vertical rise of 25-30′, and pump through 400′ of 3/4 pex to the top of the hill.
To overcome gravity and the rise of a hill and the friction of the piping material you’ll have to figure out the pressure that is built up that the pump must exceed to work properly. We had to overcome pipe friction, with 3/4″ pex pipe there is 0.81 per hundred or 400′ divided by 100 feet = 4 x 0.81 psi = 3.24 psi.
How to overcome head / or vertical rise here is a handy cheat sheet:
- 400′ of 30′ head is 12.99 lbs/per square inch. Even at 50′ of head AND the pex friction, would have been 3.24PSI plus 21.65PSI for a total of 24.89PSI.
So I looked for a pump that at 1/2 capacity to not max out the specs would be 50psi. The actual pump I ordered is this one: 8000-543-936 SHURFLO
The Solar Panels I purchased off Amazon Prime included shipping in the price and we got them for $238 for 2 panels.
See the images below of the panel build below.
I decided to leave a vent hole of about 3 inches above and below each panel to accommodate for any high winds. So instead of making this a wind break, the extra holes would allow for any air trapped behind the panel to flow around it near the top and bottom and reduce any pressure that could build up flexing glass and silica material.
We were 1 2×4 short so I bridged 2 shorter pieces together for the back base board.
Hope your project comes to life like mine did.
If I can help you feel free to contact me on our contact page.
NOTE ABOUT PRODUCTS WE USED IN THE ABOVE INSTALL. We strive to NOT promote any products or services that we do not own or have actually used. (we receive a small commission from Amazon if you use our links your price is the same as buying directly however as a referral we get credited for your purchase). Thanks for your support in advance!