Pumping to a tank for gravity feed.

WattlessWattless Registered Users Posts: 4
Hi, I'm starting to develop a system allowing us to eliminate the high power spike from pumping the deep well (1500 watts for 30 minutes). We normally choose when the breakers are on for the deep well so as not to pump when we have low DC input from solar, wind or AC from the backup generator.

Since we have a hill above us allowing for water storage at almost any selected level, my thought was to install a 500 to 1000 gallon tank at about 125 ft above the house for a little over 50psi gravity feed to the house. This where I need your opinions and advice on what is a practical and trouble free way to get the water from the well to the uphill tank.

The well is 325 ft deep with a 110 ft static level producing 2.5 GPM. The house is on the same level as the top of the well head. Worst case would then be pumping from the bottom of the well (if the solar pump exceeded the well supply of 2.5 GPM) to the uphill tank, 450 vertical. Or a best case of pumping from the 110 ft static to the uphill tank 235 ft (if the solar pump is less than the well input of 2.5 GPM. I think the lower pump flow make the most sense as it keeps the power requirement lower and I don't have to worry about the pump gong dry.

My thought was to install a solar powered pump that when the sun is shining, the pump is keeping the uphill tank full, and we have gravity feed to the house. I don't have accurate numbers on weekly water usage but think it is between 300 and 500 gallons a week.

I have 2 spare 170 watt solar panels that are not dedicated to anything else that I would like to use. We are in southern Oregon above the fog, have a horizon to horizon sun arc and just have to deal with a few long periods of low sun due to extended storms.


  • mike95490mike95490 Solar Expert Posts: 9,362 ✭✭✭✭✭
    Re: Pumping to a tank for gravity feed.


    Well, you have listed your 2 choices.
    Direct power DC/PV submerged pump only runs in sunlight. Single pump, will need to lift the entire distance (static level + tank height) for your best efficiency.
    Conventional submerged pump (240VAC will have less wire losses, and 3 wire pump is easier load on inverter than a 2 wire pump)

    I guess your pump is set down at 325' ? As your well level drops, at some point you need to make sure your pump curve is selected so you do not run the well dry.

    I've used a T in my water line, and a single 2.5" pipe (also serves as my fire hydrant line too) for pumping UP the hill, and back down. I've got a strainer in the pump outlet, to make sure blended frogs don't get up into the tank! (I'm pumping from a pond, up 180' to my tank farm)
    Since I'm doing a full time house, and have a 240VAC inverter, I used a 240VAC conventional 1/2hp pump. Inverter readout shows it pulls 1,000w while running. I've not been able to measure starting surge, but surge capacity was a reason I chose the XW inverter.

    You will have to cost out what your different options are, and what you want to do. Having 50psi water all the time, is great, not worrying if the batteries will have enough to run a pump in the am before dawn.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • cruiser guycruiser guy Solar Expert Posts: 87 ✭✭✭✭
    Re: Pumping to a tank for gravity feed.

    Look at the Grunfos SQF line. We are pumping out of a well to a tank here in Sierra Leone and we can fill the 2000 liter tank in under and hour and a half of sun. The pump also has a sensor in case you pump too fast it will shut down the pump on low water level in you well.

    I'm not sure if the two 170 watt panels will do the trick though, especially up north somewhere. We're running 1080 watts of panel for the pump.
  • TnAndyTnAndy Solar Expert Posts: 249 ✭✭✭✭✭
    Re: Pumping to a tank for gravity feed.

    Look on the NAWS website here: http://www.solar-electric.com/grsoposuwapu.html

    and download the PDF file on Grundfos pumps. Starting on pg 26, the performance curves for their various pumps is shown. Looks like 340w of panels on most of the pumps will do 2gal/min at close to 400'. If you get 4 hours of sun a day, that's 240min x 2gal/min = 480gal/day. So, basically, one day a pumping would cover your weekly requirements.....which, by the way, you might want to confirm, as that sounds a bit low for a "we" household assuming regular flush toilets, washing machine, etc.

    Personally, I'd put in more storage......I have 3,000gals myself.....because storage is fairly cheap and water is a dang handy thing to have, especially if you ever have a fire. A 1500gal plastic tank at my local farm supply store runs about 700 bucks, and I put two of them in a 10x20 insulated cinderblock building up on our hill. With that kind of storage, you can stand several weeks of bad weather, and never have to fire up a generator.

    Also, don't forget to put a wire in water line ditch for a float switch on the tanks so the pump doesn't pump when the tanks are full.
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