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Thread: picking submersable pump/ calculating resistance from a long run of water pipe

  1. #1
    DIY Junior Member kavik's Avatar
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    Default picking submersable pump/ calculating resistance from a long run of water pipe

    I have a cistern fed by a spring and there is a submersable 4" 220 v pump in it. It is located a long way from my house. The water is pumped a little over a 1/4 mile through 1 1/4 " galvanized pipe. There is probably only 60 foot elevation rise. The pump needs to be replaced and I am wondering how to calculate the resistance of the water through the pipe in with sizing the pump. I have a barn halfway to the house with water. Currently, at 60 psi showing onthe pressure guage, water will flow at the barn, but not at the house. At 90 psi it flows well at the house also. I don't know what size/stage pump is in the cistern right now.

    As an aside, I was considering a constant pressure type pump, as the water volume at the house does vary cosiderably as the pressure tank drains/system cycles- anyone have any experience with them?

    thanks
    Last edited by kavik; 12-31-2011 at 06:23 AM.

  2. #2
    In the Trades Tom Sawyer's Avatar
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    You can find charts online or from pump companies that will give you the resistance
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  3. #3
    Porky Cutter,MGWC Porky's Avatar
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    My advise is to stay away from the variable flow pumps as they are a technological nightmare. Installing a Cycle Stop Valve in the line between the pump and tank is much less expesive, all mechanical (no additional electronics), it will extend the life of your pump, pressure switch and tank and it will give you constant pressure. I think that you can find out more about it by visiting http://www.cyclestopvalves.com
    Porky Cutter, MGWC
    (Master Ground Water Consultant)

  4. #4
    DIYer, not in the trades LLigetfa's Avatar
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    The math does not add up. You lose .43 PSI for every foot of elevation, so if there really is 60 feet of elevation from the barn to the house, there should be 26 PSI loss. 60 PSI at the barn then would be 34 PSI at the house and water should flow. How much flow of course, depends on resistance. I think you need a new pressure guage.

    As for variable speed pumps, such a long wire run would wreak havoc on the electronics.

  5. #5
    General Engineering Contractor ballvalve's Avatar
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    http://www.freecalc.com/frdiresl.htm...etailCalc.y=39

    You can play with the numbers. But you should lose only 30 to 40 PSI at the end of the run unless your pipe is like most of our arteries after age 60.

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