Sandpoint, Airbubbles in water

Discussion in 'Pumps and Tanks Well Forum & Blog' started by Shallow Well, Dec 30, 2008.

  1. Shallow Well

    Shallow Well New Member

    Messages:
    16
    Location:
    Cambridge MN
    Hello all,

    I drove in a sandpoint last summer and still have airbubbles in the water. The well never looses prime even when not pumping for weeks. I replaced all above ground pipeing and have not found any leaks on the suction side. The well has a very solid Hydrolic connection I determined because the handpump has absolutly 0 kickback on the handle with great water flow. I believe the point is sitting in a very very fine sandy aquifer.

    When running wide open it pumps airbubbles steady. But when I hook up the pressure tank and run it at around 36 psi it does not pump any noticable airbubbles but still has good water flow.

    With a 1/2 hp pump running full flow with 0 psi it pumps exactally 5 Gpm for hours with a suction of 23.5" hg on the vacuum gauge (which translates to 26.55 feet of suction lift).

    The point is 25.6' deep with a static water level of 16'4". The top of the screen is a around 4.5' below static water level (can not drive point any deeper due to hard layer).



    My First question is: Could I be overpumping the well and drawing small ammounts of air through the well screen due to drawdown of the water level above the screen.

    Second question: Gould's website suggested installing a ball valve on the suction side to prevent over pumping a low yield well but not to throttle to more than 22'' HG (or 25 feet suction lift). Does anyone have any experience or suggestions on this being that im already at 23.5"Hg.
    Last edited: Dec 30, 2008
  2. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    Goulds should retract that statement. Never put any valve except a check valve in your suction line. And the check valve should be as close to the well and as far away from the pump as possible.

    If you have bubbles, you have an air leak. The reason the air goes away when the pressure gets up higher is that the pump is not pulling as hard and is less likely to pull the air.

    Five gpm is not a lot of water from any well, but maybe your pump can't do more than that pulling from 16 feet. A pitcher pump should do easily 10 gpm if the handle doesn't kick back at all.

    Forget the vacuum gauge, it will just confuse the issue. As long as the water level is less than 25 feet, the pump will get all it can within it's limits if the well allows and your pitcher pump report sounds like you have a good producer.

    bob...
  3. Shallow Well

    Shallow Well New Member

    Messages:
    16
    Location:
    Cambridge MN
    Up here in East Central Minnesota we do not get much more than 5gpm out of our sandpoints. Both my pitcher pump and jet pump produce the same 5gpm. I know of a few people in the area that are getting about the same or less yield as my well.

    The University of Minnesota extension office even states, "However, a wellpoint should not be expected to yield large quantities of water; 5 gallons per minute would be a reasonable yield".

    www.extension.umn.edu/distribution/naturalresources/DD0951.html

    Is my thinking correct that by installing a ball valve on the suction side to throttle down the pump would increase the vacuum at the pump higher than my current 23.5"Hg which is bad for the pump. Or am I wrong and would it decrease the inches of HG and thus prevent my pump from overpumping the well which could be causing the airbubbles. My cast iron Redlion pump is rated to pump around 8gpm from 17 feet. (www.redlionproducts.com/v4/pumps_water.htm)
  4. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    Unless you have nothing other than extremely fine sand, I don't see why that would be the case. Water travels through sand and gravel at differing rates depending on the porosity of the material. If it's all fine sand and a 100 gauze screen had to be used, I can see why 5 gpm would be the norm. If the sand is more course or is closer to gravel, an 18 slot screen or larger could be used and you could expect closer to 20 gpm.

    The University making a blanket statement like this:
    is not well thought out in my opinion.

    Do you know what kind or size of screen you used? If you do, you will be the first one I have asked that question of that actually had an answer.

    bob...
  5. Shallow Well

    Shallow Well New Member

    Messages:
    16
    Location:
    Cambridge MN
    The screen is a high quality 40" Full Stainless steel continous slot, 10 slot that can't be found in big box or hardware stores.
  6. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    All right! You get the prize, your the first one with an actual answer that resembles an actual Slotted Well Point.

    I have seen 12 to 15 gpm from 10 slot screens time after time. It's not unheard of and more the norm that the exception.

    Sounds like you have an air leak somewhere. They are next to impossible to find. If you used PVC pipe you can use glue around each fitting while the pump is running, this will suck glue into the air leak and usually heal it.

    bob...
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