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  1. #1

    confused about pump and wire.

    I have an old hand dug well on my property it is 3'-6" in dia. 50' deep. depth of water ranges from 20'-30'and puts out about 50 gpms.I would like to install a submersible pump and pressure tank.The total lift from pump to house is 85' the problem is that its almost 1900' from electric panel to pump.I have been told so many different things as to what size pump and wire to use.I was told by one person at an electrical supply store that a #2 urd direct burial aluminum wire would run a 3/4 or 1 hp 240 volt pump.another guy told me that would'nt work because the pump draws three times more amps at startup than when running.I would like to have good pressure and around 10 gpms at an outside hydrant at the house.one other option i have is to have the electric co. run service from a pole about 400' away and put a meter at the well.I was thinking i could build a pump house and have the pressure tank there at the well.Any and all information will be appreciated.

  2. #2
    You say the 'lift' is 85 feet. Is that how far the well is from the point of use ? or is that the difference in elevation ? Is the point of use _also_ 1900 feet away ? If so, I should think the piping is going to be as big or bigger a problem than the wiring.

    I don't know the electric too good, but I can tellya this: That's gonna be some mighty big wire...

  3. #3
    Pump guy speedbump's Avatar
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    TII is right about the pipe size.

    I would look into the meter at the well myself. You can go 1610 feet with #8 copper and 2510 with #6 copper. That means you can use a formula to figure out how much #8 and how much #6 you will need. I would stay away from aluminum. The pump I'm suggesting is a 1/2hp 10 gpm sub. It's a very standard pump and will give you what your looking for providing you use at least 1-1/2" pipe. Two inch would be more ideal.

    The pressure switch and tank must be together, that's why the switch and tank should be at the well and the meter at the well is a better idea. I think they do the install for free, don't they?

    The pump: Submersible Pumps

    bob...

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  4. #4
    The meter installation is free, the owner provides the base, or pole.

    However since this is not a residence the monthly base charge is higher (not the KWH charge).

    Rancher

  5. #5
    Pump guy speedbump's Avatar
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    How long do you suppose it would take to offset the higher fee as oppossed to the cost of the wire?

    bob...

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  6. #6
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    I can tell you here the basic facility charge for a house is about $7 and for my well $15. In my case I will eventually move the tank, switch and all next to the house and run the pump from my home's panel.

  7. #7
    I was going to say my meter charge for the barn is about 13, house is less than 10, so say $150/year extra for the service. You also have to calculate in the power loss in that 8AWG cable to compare apples to apples.

    Rancher

  8. #8
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    50GPM? I wish I had a well like that! I too have a 3'-6" well, but it only makes about 3/4 GPM, and is 29 feet deep, with just several feet of water above the pump. I'm looking for someone who still drills those types of wells, to see about getting it dug deeper.

    If you can use very large pipe to run water to the house, that pump will make even more than 10 GPM because it isn't having to pump water very high with a well like yours.

  9. #9
    quote:Originally posted by speedbump

    ...providing you use at least 1-1/2" pipe. Two inch would be more ideal...
    Looking at the chart that Testman provided a link to in another thread, and using 2000 feet as the length of the pipe, at 10 GPM, 1-1/2" pipe will have 62 PSI pressure drop, while 2" will only have 18 PSI drop.

    Now I'm confused too! Let's say the pressure switch is set 40-60 for the sake of this discussion. If you use 1-1/2" pipe, wouldn't that mean you won't get any water out the other end ? that's impossible... does that mean instead that your pump isn't up to the task, and you would get less GPM ? say 8 GPM at miniscule pressure ?

    Bob, where can I find the pump curves for the SFH series pumps ? National's site doesn't seem to have them.

  10. #10
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    For 10GPM, and using a 1.5 inch plastic pipe, the chart is showing .72 feet of head per hundred feet. 2000 feet would mean .72 X 20. Now we have a 14.4 feet of head loss. Next, it says to calculate psi, you multiply feet of head by .4335

    So I guess it would mean a drop of 6.24 psi. But if he has a pump that will be putting out 20GPM at the source, then it looks like there will be a far more dramatic slow down from that rate, if using only 1.5 inch pipe. It then is showing a 22.6 psi drop. So a 2 inch pipe is definitely the way to go. But I still can't figure to how to predict the flow loss from the calculated pressure loss. Example, if a 1.5 inch pipe is used, there will be a 22.6 psi drop in pressure if his pump will put out 20GPM (Actually, it won't do quite that much, but just for the sake of explanation, lets say it did) Then on the other end of that 1.5 inch pipe, 2000 feet away, what will the maximum flow rate in GPM be?

    http://www.plumbingsupply.com/flowchart.html

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