Overdrawing a shallow well?

Discussion in 'Pumps and Tanks Well Forum & Blog' started by JVance, Dec 11, 2011.

  1. JVance

    JVance Homeowner

    Messages:
    28
    Location:
    Johns Island, SC
    I am trying to troubleshoot some issues with the well in our new house (we have a few, but this would seem to be the logical first issue to tackle). We live on a coastal island, have a shallow well (34' deep), Goulds 1HP jet pump (set to 30/50 PSI start/stop pressure) and 120 gallon tank. The pump sucks a fair amount of air, as observed through the clear housings of the filters between the pump and the tank. From what I've read, air is not friendly to a jet pump, but it nonetheless moves enough volume of water and does not lose its prime.

    There is no information scribed for gpm on the placard in the well-head, so I don't know what flow the well is rated; but, I am concerned that this pump may be overdrawing the well. There generally appears to be more air in the filter housings at lower tank PSI (e.g. when the pump is capable of moving more gpm), and less air at higher tank PSI (e.g. when the flow is reduced). Do these observations suggest the pump may be overdrawing the well? If so, would restricting the discharge flow be the solution? What then is a recommended flow restrictor/regulator, aside from partially closing the ball-valve between the pump and tank?

    Thanks in advance for your advice!
  2. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,922
    Location:
    NW Ontario, Canada
    A shallow well jet pump cannot possibly overdraw a 34 foot deep well. The laws of physics forbid it. Could it be that it is setup for deep well operation and you omitted that detail? If it is a shallow well pump and the footvalve is set deep enough, then the air must be from a suction side leak, not from overdrawing.
  3. JVance

    JVance Homeowner

    Messages:
    28
    Location:
    Johns Island, SC
    Absolutely not set up as a deep well.

    I pulled the placard, cleaned it off and found some more info. Casing depth is 25 feet; screen interval is 25 to 35 feet; gravel interval is 24 to 36(?) feet; static water level is 7 ft; and, the yield was estimated to be 5 gpm (1/2 to 1/3 the rating of the pump???).

    Could it be a leak on the suction side? Maybe...but with the amount of air I'm observing, if there was a leak between the pump and the foot valve, there would be no way the system would hold any pressure. There are times the pump is moving water and there is no air visible in the filter housings, then 10-15 seconds later, ~1 liter of water is displaced by air. If that much air can get in through a leak under vacuum, then what's stopping the tank from bleeding down under 40-50 psi of pressure?
    Last edited: Dec 11, 2011
  4. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,922
    Location:
    NW Ontario, Canada
    Some people have topside checkvalves and those would prevent a suction side leak from leaking under pressure. If you are sure there is no other checkvalve and it holds under pressure then it's entirely possible the footvalve is not set deep enough and you are overdrawing the well.

    I would set the footvalve lower so that the pump cannot lift as fast from the greater depth when the level drops under heavy draw. I would also raise the min and max on the pressure switch slightly to reduce the GPM the pump produces.
  5. Texas Wellman

    Texas Wellman In the Trades

    Messages:
    523
    Location:
    SE Texas-Coastal
    There should be no filters between the pump and tank. Pipe it straight in.

    Install a throttle valve between the pump and tank. Start with the valve wide open (have a pressure gauge at the pump). When you hear the pump "lose out", close the valve back. Close the valve until the pump picks back up. Once the pump picks back up slowly, slowly open the throttle valve until you find the balance.



  6. JVance

    JVance Homeowner

    Messages:
    28
    Location:
    Johns Island, SC
    1) I don't want sediment in the tank, 2) the filters are plumbed in parallel so the resistance has been halved, and 3) it's not the cause of the problem.

    Suffice to say, if no filters were plumbed between the pump and the tank, I would not be aware of this problem...


    Going shopping...
  7. JVance

    JVance Homeowner

    Messages:
    28
    Location:
    Johns Island, SC
    There may be a top-side check valve, but if so, it's under ground somewhere between the well head and the well stub in the garage. At the well head, there is a 2nd pipe with a ball-valve that appears to tee into the well pipe as they go into the ground (I'm assuming this is for inspection/sanitizing). If I open this ball-valve when the tank is under pressure, there is no back-flow of water through this valve. Would this confirm there is a check valve between the pump and well, or does this 2nd pipe not connect to the well pipe (e.g. does it run parallel to the well pipe down the casing)?
  8. valveman

    valveman Moderator Staff Member

    Messages:
    4,426
    Location:
    Lubbock, Texas
    The second pipe is probably making it into a "deep well jet pump". There should be a check valve on that jet assembly where the two pipes go together.
  9. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,922
    Location:
    NW Ontario, Canada
    If there are two pipes from the well to the pump, it is setup as a deep well pump as Cary said in which case the injector/ejector/eductor is down the well.
  10. valveman

    valveman Moderator Staff Member

    Messages:
    4,426
    Location:
    Lubbock, Texas
    Usually yes. But I have seen the ejector placed above ground and a check valve attached before you put a single pipe down the well.
  11. JVance

    JVance Homeowner

    Messages:
    28
    Location:
    Johns Island, SC
    There is only one pipe that exits the well head that goes to the pump. The second pipe ends at the top of the well. From what's visible through the open ball-valve of that second pipe, it tees into the well pipe a few inches below the seal.

    Again, I'm assuming the purpose for this second pipe is for inspecting/sanitizing the well. It stops at the well head and doesn't go anywhere; otherwise trying to sanitize a well with a single, glued PVC pipe (and unknown check valves between the pump and well) would be fruitless...
    Last edited: Dec 13, 2011
  12. JVance

    JVance Homeowner

    Messages:
    28
    Location:
    Johns Island, SC
    Fortunately, I shut off my pump before leaving home this morning. The pump was running, but the pressure in the tank had not changed for several minutes. The body of the pump was very hot and there was no air in the filters. To check if the pump was moving water, I closed then opened the ball valve between the pump and the tank; it produced no change in tone to indicate that the flow of water had been impeded by the ball-valve: the pump was not pumping any water. (side note: this explains the failure of a few PVC fittings threaded into the pump body; I thought that I had over-torqued them on assembly, but heat likely played a role in the threads failing)

    When I shut the pump off, there was no (audible) back-flow of water from the tank back through the pump and down the well, such as what I hear when there is air in the well pipe. This would seem to indicate that 1) the well pipe was free of air, and 2) I drew down the well far enough that the pump could not draw up the water. I'm beginning to think the root of the problem is that I have a crappy shallow well rated for 5 gpm yield, and a 1HP pump rated for 2-3x that flow. [edit: just got off the phone with the guy that drove this well...symptoms are consistent with too much pump for a low producing well. We may either throttle down the pump or drive another well (or both). They will be out to inspect the well tomorrow.]
    Last edited: Dec 14, 2011
  13. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,922
    Location:
    NW Ontario, Canada
    When you open the well, measure how far down the footvalve is. If you set the footvalve deep enough, the pump will not be able to draw it all the way down to suck air and therefore will become self-regulating. The higher it has to lift the water and the higher the pressure it pumps up to, the lower the GPM.
  14. JVance

    JVance Homeowner

    Messages:
    28
    Location:
    Johns Island, SC
    The foot valve would appear to be low enough.
  15. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,922
    Location:
    NW Ontario, Canada
  16. JVance

    JVance Homeowner

    Messages:
    28
    Location:
    Johns Island, SC
    Low enough to cause the problems I described this morning? At this point, I don't understand why this problem is inconsistent. One day, all I get is air and water; the next, there is no air in the lines and the pump appears unable to move any water.

    I hope the professionals are able to diagnose the problems. Our next-door neighbor has had no issues with his well for the last two years; whereas, the neighbor 100 yards over has 3 well heads feeding one pump.
  17. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,922
    Location:
    NW Ontario, Canada
    I'm sure if you throw enought money at the professionals, they will sort it out.
  18. JVance

    JVance Homeowner

    Messages:
    28
    Location:
    Johns Island, SC
    I'm content in the fact that I can bathe in your arrogance this evening; it's better than having no water at all.

    I spent the evening digging a trench to the well line, checking joints for leakage. Tomorrow I will continue until I reach the foundation and can proceed no further.

    I will gladly pay an expert when my time runs short and my family's patience wears thin. The well servicer should be out tomorrow, and hopefully he can provide a few explanations for the problem. He installed my well and my neighbors' wells; at the very least he can add some perspective from his experience with this coastal island region.
  19. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,922
    Location:
    NW Ontario, Canada
    Not arrogance, ignorance.

    I have suggested several times that the footvalve may not be set deep enough, but then the depth is a mystery to me since you will not divulge it's depth.
  20. JVance

    JVance Homeowner

    Messages:
    28
    Location:
    Johns Island, SC
    "Divulge" assumes I know the depth to begin with :rolleyes: I didn't drive this well, and the only specifications I have for the well were the data listed on the placard inside the well head. Determining the depth of the foot valve isn't exactly trivial...

    Yeah, sometimes the symptoms appear consistent with the foot valve being set too high; other times, the symptoms don't support this (like when there is no air in the pipe and the pump cannot move the water, consistent with the foot valve being set deep enough and the water level below the ability for vacuum to pull the column up). And if there were leaks in the well pipe, the pump would suck air all the time.

    Hopefully, the well servicer's records will reveal the depth of the foot valve, since no such data is on the placard.
    Last edited: Dec 14, 2011
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