Water pump question.

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System
System Posts: 2,511 admin
in Solar Water Pumping #1
Howdy folks,

I have a small 640 sqft Rammed Earth 'casita' (cabin on the desert) which is 300 feet from my water tank. The water tank is 5 feet above the casita and I have installed a 1-1/2" water line from it to the casita.

There is no grid power avail and I will eventually be installing a Solar Power Unit for the casita and for a pressurized water tank. But that is about 3 years away.

Most likely, until then, I will be using a generator to power the casita. Is it pracitcal to use a small water pump located at the casita to get enough water pressure for the showers and faucets in the casita?
And if so, what size and make would you recommend?

Kind regards,
ki-e-ta
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
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    Re: Water pump question.

    Have you actually tried it ? It's a big pipe, and 5' isn't a lot, but you should get a good flow. The hang up baggies/Solar Showers are only a foot tall, and the flow well enough for a weekend camp.
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  • Telco
    Telco Solar Expert Posts: 201 ✭✭✭✭✭
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    Re: Water pump question.

    Did a little checking, water generates .433PSI per foot of elevation. A 5 ft rise will make about 2PSI. Typical city pressure runs around 40 to 50PSI, requiring a tower of 90 to 115ft, which is impractical.

    A small pump should be able to provide the pressure you want, without wasting too much power. 30 years ago I lived in a country house that was on well water, we had a pump some 200ft in the ground to get the water up, then a pressurization pump to supply water pressure. Worked great, and our power bill was usually 40-60 bucks for a 2100 sq ft house. Other houses in the area had 100-150 dollar bills, for comparison. No idea how much power the two pumps used, but 30 years of advances combined with your much smaller need, you should be able to find a pressurization pump that uses almost no power (might even be able to run off a single solar panel with a single battery) that will provide at least 40PSI.

    A shop that sells parts for large boats would be a good place to look, as they need to have enough water pressure to take showers, cook, ect, yet be able to run off the boat's batteries without killing them. This site describes the Surflow pump, which requires a 15 amp breaker at 12V, and also recommends an accumulator tank.

    And, if the water source were moved up a few more feet, it should provide even more pressure. If there were a way to make the water tower 20ft tall instead of 5ft tall, then the pump would have 10PSI coming in, so you could either have 50PSI out of a 40PSI pump, or go with a lower pressure pump. The pump pressure should be a differential between pressure in and pressure out.

    Hope all this helps, I'm by no means a water expert.
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