Best way to increase GPM from existing deep well

Discussion in 'Pumps and Tanks Well Forum & Blog. Water is life.' started by howardB, Apr 7, 2021.

  1. howardB

    howardB New Member

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    Apr 7, 2021
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    Virginia
    I have a 2.5 gpm deep (400’) well that I’d like to draw more from. It’s consistently delivered 2.5 for decades at 104’ (nearby river depth)
    The two options I’m considering are some sort of fracing or an additional well. Concerned fracing might compromise existing well since it’s so low flow..

    tnx
     
  2. valveman

    valveman Cary Austin Staff Member

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    Pump Controls Technician
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    Lubbock, Texas
    2.5 GPM is 3600 gallons per day? Do you need more than that? If not, a cistern storage tank and a booster pump would let you utilize all 3600 gallons per day anyway you want to use it.

    If you need more than 3600 gallons per day the well will need to produce more or you will need an additional well to add in. But you say it is 400' deep and delivers water from 104'? Could the pump be put deeper? The well may make more water from a greater depth.
     
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  4. Reach4

    Reach4 Well-Known Member

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    Are you planning to do a lot of irrigation? For house use, a deep well use has significant storage ability. Replenishing at 2 gpm would normally support a big house. Did you run dry at some point? If so, maybe lowering the pump would be worthwhile.

    With a 4 inch well and a pump hanging on 1 inch pipe, there is about 58 gallons of storage in 100 ft. With a 5 inch well, about 95 gallons. With a 6 inch well about 140 gallons. These storage numbers do not include new water coming in during the draw.

    These gallon numbers are a little lower than you will sometimes see, because it subtracts the space for the 1.315 inch OD drop pipe.
     
    Last edited: Apr 7, 2021
  5. valveman

    valveman Cary Austin Staff Member

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    Actually, the drop pipe is full of water too. :)

    Also, the well bore is larger than the casing, and can be considered storage as well.
     
  6. Reach4

    Reach4 Well-Known Member

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    Can't empty that out normally, so it doesn't count IMO.
     
  7. howardB

    howardB New Member

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    Apr 7, 2021
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    Virginia
    Thanks for all the input.
    The flow rate is more of a demand and pressure issue (high flow rates can exceed the pumps recovery rate). It's largely irrigation (flower beds mostly) when it does occur. We do use drip irrigation and sequence it throughout the day, which made a huge difference in water usage, but I'd like to be able to provide more flow without drawing the system down too much. I monitor the pressures, flow and well depth in realtime so I probably worry too much :), but I don't like it getting below 140+'. The pump is at 350' I believe, so I realize there's more water available, but I like to think of it as a reserve and find more on demand water vs storage (ie cistern).

    Am I correct in assuming that fracking can cause as much damage as improvement? Our last earthquake (albeit a small one) caused a lot of extra silt, although no change it flow. I'm pretty sure we're closely linked to the nearby river, as when we have a large rainfall that causes the river to rise several feet, I can see our well level go up as well within a very short period..

    If I did install a new well, would I be able to connect it in parallel to the existing system (assuming the pressure switch points were set appropriately)?

    Thanks!
     
  8. wwhitney

    wwhitney Well-Known Member

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    Location:
    Berkeley, CA
    Seems like zoning that out to reduce the peak demand, and spacing out the irrigation, would be a lot simpler than digging a new well or adding storage.

    Cheers, Wayne
     
  9. valveman

    valveman Cary Austin Staff Member

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    You are not getting the full potential of your well. Wells will make more water when the water level is pulled down. Pulling the water level down close to the pump causes the down hole pressure to decrease, which lets more water flow into the well. Since you can monitor the well level, try lowering the limit to 300'-325'. I will bet you get twice as much water as when trying to keep the level above 140'.

    But yes if you add another well you just need to stagger the pressure settings so the best well comes on first at the highest pressure. Like this.

     
  10. howardB

    howardB New Member

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    Virginia
    Good comments..
    I already space out the irrigation, it sequences itself automatically depending on the soil moisture and weather reports. I'm sure I'm overly concerned, I just like to have spares of everything :)

    I haven't dropped it that low, but I've accidentally (hose left on before I built a hi flow/low well level alarm) dropped it down to the 250' area several times. When I graph the refill rate, it's almost identical to the normal refill rate (2.5 gpm) which is curious. I think it's partially due to why I have such a slow flow rate, as the ground content at 104' (where the water is sourcing from) must be somewhat restricted. My normal depth sits at 96.5' (except when the river rises significantly), and I attribute that 7.5' rise to the pressure of the inlet water (~3 psi) which isn't all that much push..

    Thanks
     
  11. Bannerman

    Bannerman Well-Known Member

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    While you said the well is 400' deep, how deep does the casing extend and how deep is the screen located? If the casing extends to 400' and if the screen is located near the bottom of the casing, then water will only enter into the casing through the screen and through the open bottom end of the casing and so will rise within the casing to the static level. If pumping the water level down closer to the screen location, the well may recover faster than when pumping down to only 140 or 250'.
     
    Last edited: Apr 8, 2021
  12. LLigetfa

    LLigetfa DIYer, not in the trades

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    It sounds like the 400 foot depth only serves as expensive storage. If the water enters at 104 feet, then pumping lower than that will not increase the recovery rate.
     
  13. valveman

    valveman Cary Austin Staff Member

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    Pump Controls Technician
    Location:
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    There maybe other zones below 104' that are also producing some flow. Pulling the water level down will let you access this water as well and may let you pump considerable more water from that well. If nothing else you can utilize water from the extra storage in the well.
     
  14. Bannerman

    Bannerman Well-Known Member

    Joined:
    Mar 19, 2014
    Location:
    Ontario, Canada
    This assumes 100% of the water is actually entering the casing at 104'.

    With a 400' well with the pump placed at 350', I anticipate water will enter the casing at a greater depth.
     
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