Advice needed for building small pool on farm

KeninOntKeninOnt Registered Users Posts: 5 ✭✭
Hello... I am building a small concrete/tiles (520 gallons) cooling-off pool for my wife and I on our farm. Where I have dug the hole and done the landscaping is far from AC power. I have been unable to source out any kind of small solar pool pump for our needs. There are big expensive solar pool pumps but they are total overkill.

I have no experience working with water pumps. I believe if I use a 5 GPM 12v pump and 1/2" lines that I could cycle and filter the water once a day running the pump for 1.5 hrs.

Can somebody please provide me with any advice regarding the pump that could be used for this application. Thank you!

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,235 admin
    Are you OK with daytime power (solar panels only)? Or do you want to pump in the dark too (+battery bank)?

    In general, if you can pump during the day, a solar panel=>water pump (or solar panel=>Variable Frequency Drive=>pump) is going to be less money and more reliable (no battery bank to purchase and service, spend more money on pump motor+VFD).

    If you want some (for example) LED lightning (radio, etc.)--A very small solar+battery system could work for you.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • KeninOntKeninOnt Registered Users Posts: 5 ✭✭
    I am open to a solar panel=>water pump or a solar panel=>12v battery or even a 24v system depending on the water pump. The water pump is the crucial component in this system I figure so I am starting with the pump and working from there. I have been researching water pumps for a few days and do not know which pump would be best suited for our needs.

    The pump seller web sites I have sent questions to regarding "selecting the correct pump for your application" have not responded so I thought I would try here.  Thanks!
  • BB.BB. Super Moderators, Administrators Posts: 32,235 admin
    I do not know enough about the various pumping options out there. An RV pump might last a few years between rebuilds (assuming does not run more than a few hours per day???).

    If you are going to use a sand filter, the re-circulation pumps (used for radiant heating) probably do not develop enough head (pressure)--You need >~10 PSI+Lift I think?

    Hopefully, some folks here can make some pump recommendations.

    Or call our host NAWS and ask them for help (sorry--really out of my depth here)... RV pumps usually not too expensive. You can add a linear current booster (more or less matches the output of a solar panel to the IV curve of the DC pump motor--Not cheap, but cheaper than batteries+charge controller):

    http://www.solar-electric.com/residential/solar-water-pumping/pump-controllers-current-boosters.html

    There are very nice solar powered well pumps--But they tend to be pretty expensive... One of the lower price units I have seen (no nothing about):

    http://www.solarpumps.com/solar-pump-info-page.html

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited July 2016 #5
    Consider building a largish sand bed that is elevated above the pool.  Then you only need to lift the water about 1 meter where it will trickle through the bed and gravity return to the pool.   I'd look at a DC-DC converter to maintain the right voltage and then a low head, high flow , brushless DC pump (search ebay).   Or one of the pumps with a built-in MPPT controller.  Pumping would happen whenever the sun is shining.

    I am available for custom hardware/firmware development

  • KeninOntKeninOnt Registered Users Posts: 5 ✭✭
    NAWS replied to my e-mail and pointed me to SUN Pumps solar pool pumps, which unfortunately are for 15k ga+ pools. The other companies I contacted have yet to reply.

    ====> sand bed

    We first thought about building a natural pool with pond filtering ect. but we have a forest farm and there are a lot of bugs and wildlife here. So we went to walmart and got a small pool, which was great, but something ate into it last winter while in storage. So we decided to build something nice ourselves.

    I called Aquatec, who were very helpfull and suggested I contact AEE Solar regarding a centrifugal circulation pump. I did but the person who is the pump expert is at a trade show, back Monday.

    I did however source out a filter system, which is necessary for determining the pump requirments and found the highest flow rate for a non-pool filter is Rainfresh at:


    If I use a 1 micron filter I can get a flow rate of 40GPM, the highest I could find.

  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited July 2016 #7
    A sand filter doesn't have to have any relation to a natural pool  - it's just a cost effective filter medium that allows large and pressure efficient filters.   You probably want about 2 GPM for your very small pool - 40 sounds crazy.

    I am available for custom hardware/firmware development

  • KeninOntKeninOnt Registered Users Posts: 5 ✭✭
    edited July 2016 #8
    I'm simply assuming that the higher the flow rate of the filter the less drag and back pressure for the pump. I'm also assuming that at 2 GPM it would take 4.5 hrs of pump run time to circulate the water once a day. At 5 GPM it would take around 1.5 hrs, which I would do at 3 1/2 hr intervals through the day/night. This is to get around over heating the pump. Are my assumptions correct or am I way off here? 
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,076 ✭✭✭✭✭
    I think Jon's advice is good and you are missing how a sand filter works. There really is not any back pressure as you just fill the area above the filter and it drains thru down to the pond. 
    Read up on sand filters and you will see the light. Forget about the plastic filter. A decent sand filter design is very efficient, inexpensive, and easy to fabricate. Been around since the first guy got sick drinking out of a pond.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    I'd pump whenever the sun is shining.  This won't overheat any decent pump.

    I am available for custom hardware/firmware development

  • Dave AngeliniDave Angelini Solar Expert Posts: 6,076 ✭✭✭✭✭
    I think he is talking about a small 12V rv pump.  I would use a timer as they have a finite life  (diaphragm replace) when running continuously.

    How far away is the 230vac BTW.  Even with small wire and a bit of loss you can go 500 feet or more pretty painlessly.

    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited July 2016 #12
    A brushless, DC, centrifugal pump, 2 GPM, 1 meter head should last a long time.  Sometimes called a fountain pump.  Easily powered with solar (although wiring is good too).

    I am available for custom hardware/firmware development

  • KeninOntKeninOnt Registered Users Posts: 5 ✭✭
    ==> Sand Filter

    A pool, regardless of size requires circulation to work efficiently. The best case scenareo is water output = water return. Standard pool sand filters are engineered with their own pumps to achieve flow balance in the system. I believe it could be possible to build a sand water filter that could drain and match pool water output but it would require too much experimentation and work to build. I can go to amazon right now and order a small filter and cartridge.

    Filters come in various micron sizes giving ranges of 2 GPM - 40 GPM thus giving me some leeway in balancing the flow at the filter stage.

    ==> How far away is the 230vac BTW.

    250-300 ft. We would have to bury the line. Lots of trees and bedrock. If we did it "to code" it would be too much work and $$$.
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