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Thread: Well Physics

  1. #1

    Default Well Physics

    Could someone please explain the difference between the filling speed of water originating from deep within a well vs from an opening higher up within the well..

    i.e.

    If a 1000ft well has a 2GPM yield would the water rise to the static level of 300 ft slower if the source is at 850 ft vs if the source is an opening at 500 ft---In other words how does the weight of the total water being pushed to the top (static level) affect the filling speed (recovery rate) ?

    Thank you--I hope the question is clear ?

  2. #2
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by weather777 View Post
    If a 1000ft well has a 2GPM yield ...
    At what opening level?

    If the pressure at 1000 ft can drive 2GPM into the well, the pressure at a higher level would drive less ... and the rate of flow at any point of entry will slow as the achieved level in the well increases.

    To see that from the other end: Think of a backyard swimming pool being drained. A hole at the bottom will have the highest pressure, and that pressure will decrease as the level in the pool decreases.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default water

    The factor that counts, and it is basically the important one, is the difference in elevation between the dynamic water level and the faucet opening. Below that point the water on the outside of the pipe balances the water inside the pipe to that same level.

    Last edited by Terry; 08-15-2010 at 12:00 PM.

  4. #4
    DIY Junior Member Robert444's Avatar
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    Would the dynamic water level be the water level attained when the system has been pumping for a few minutes? As opposed to the water level when the pump is shut down?

  5. #5

    Default

    This is the scenario :


    The well is 1000 ft deep with a static level of 300 ft and yield of 2.2 GPM.We were told the water was hit at 800 ft.Being on a very tight budget the pump was dropped to 640 ft (Red jacket 1.5 HP 8GPM).We are now being told we need to drop it to 980 ft or will run out of water since the water was hit so low in the well and the fill rate will be slow given the weight of the total water being pushed to the top.It was said had the water been hit at a higher level it would not be an issue.The additional cost are substantial requiring a special type pump and cannot afford it.We only use about 200 gallons/day.
    Thank you

  6. #6
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by weather777 View Post
    We are now being told we need to drop [the pump] to 980 ft or will run out of water since the water was hit so low in the well and the fill rate will be slow given the weight of the total water being pushed to the top. It was said had the water been hit at a higher level it would not be an issue.
    Lowering the pump will allow you to pull and use more of the water "in storage" that has already entered the well, and pulling that greater amount of water out of that "storage area" will let the well re-fill as quickly as possible. However, you will only run out of water if you use up all the water above the pump and then exceed the amount the well can continuously produce ... and yes, that might be slightly more below you 800ft level.
    Last edited by leejosepho; 01-22-2009 at 03:34 AM.

  7. #7
    Moderator & Master Plumber hj's Avatar
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    Default well

    The dynamic water level in the well is the lowest point the water reaches while the pump is running. At that point the water entering the well equals the amount being pumped out.

  8. #8
    Like an engineer alternety's Avatar
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    Although the well flow rate is on the low side, it will easily supply your daily needs when spread evenly over 24 hours. 2gpm X 60min/hr X 24hrs = 2880 gallons/day. It is rate of withdrawal that is biting you. Right now you are using 260' of the well as storage now (e.g., 260' X volume of water in 1 ft of your well pipe). I probably would put protection on the well pump for running dry since your pump could pull the water level down to itself.

    You might want to price/evaluate an unpressurized storage tank and pressure pump instead of moving the pump in the well. This also leaves a bit of fairly accessible spare water if you have a well problem.

  9. #9

    Default

    Alternety

    Would the storage be 340ft i.e. 640-300=340 or is there some additional loss making it 260 ft?

  10. #10
    Like an engineer alternety's Avatar
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    Damn negative numbers.

    -300 - (-640) = 340 difference.

    You are right.

  11. #11
    Previous member sammyhydro11's Avatar
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    Alternety, if you asked him what size well he has,that is you figure out how much water is available to him. But i guess that would be a question to be asked by a hole driller and not a plumber!

    So what size well is it?


    sammy

    www.tylerwellandpump.com

  12. #12
    Like an engineer alternety's Avatar
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    Actually the (e.g., 260' [corrected to 340' in previous discussions] X volume of water in 1 ft of your well pipe) covers that. I assumed that anyone could figure out how that is done and that it involved the diameter of the well bore. I am sorry I assume too much very basic knowledge.

  13. #13
    Previous member sammyhydro11's Avatar
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    Here we go...another plumber here that thinks he's a well guy. You board with the plumbing forum or something?

    sammy

    www.tylerwellandpump.com

  14. #14
    Like an engineer alternety's Avatar
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    For a well guy that would have to be bored.

  15. #15

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    Its a 6" pipe and have been told each ft is about 1.5 gallons

    340ft x 1.5gal = 510 gallon reserve

    Is that correct?

    Thank you

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