Pump/pressure tank detective needed

Discussion in 'Pumps and Tanks Well Forum & Blog' started by ngermain, May 4, 2011.

  1. ngermain

    ngermain New Member

    Messages:
    2
    Location:
    Alberta
    Hey guys,

    My dad and I have a perplexing water problem that we can't reason out. Hoping there's some detective out there...

    We have a shallow well and a jet pump, about 20m head to the house, a pressure tank and pressure switch in the house. System had been working great for 15+ years (same pump and tank too!), pressure switch is set from 30-45psi.

    Here's the problem: Starting with a full pressure tank, we turn on some taps, water flows at a good pressure, the pressure gauge needle falls slowly as is expected. When the water pressure gets down to 30, the pressure switch makes an audible click but then instead of water rushing in and pressure going back up, the pressure falls fast to about 10psi and continues to trickle out the taps for hours. The pressure does not go up until we turn off all the taps. Once this is done, the pressure goes up fast again to 45psi and the cycle repeats.

    ??

    The pump seems strong since it can pressure up fast to 45. The pressure switch (which we replaced brand new with no effect) is clicking at the right times.

    Why would pressure fall fast at 30psi after the switch clicks? Why would the pump only start back up when all the taps are closed?

    Any suggestions would very appreciated!!
    Thanks
  2. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,826
    Location:
    NW Ontario, Canada
    I am going on the assumption that you have a bladder tank and put forth one theory. If there is too much precharge on the tank, it runs out of reserve at 30 PSI. The pump uses water to make water, and having run out of reserve, the tank cannot supply the pump with the needed water.

    Another theory is that the tank is waterlogged and as such has lots of water but still has no reserve.
  3. ngermain

    ngermain New Member

    Messages:
    2
    Location:
    Alberta
    Thanks for the reply!

    Not too sure what you mean by the pump needing water to make water.

    Note that I think my terminology is wrong about the "jet pump". Someone else told me it's actually a submersible pump. It is completely submerged in the well water, one output pipe coming off of it, the other end is the intake, it's a 3' long metal cylinder shape.

    Does that sort of pump need a minimum back pressure to start pumping up water? That could explain it...

    So then I should bleed some air off the tank? Or lower the max pressure down from 45?
  4. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,826
    Location:
    NW Ontario, Canada
    My "use water to make water" comment was predicated on it being a jet pump. Submersibles work on a different principle but those too may have a performance curve where they produce more GPM with a bit of head pressure. Of course it can vary by brand and wear.

    None the less, I would try removing a bit of air from the bladder. I don't think lowering the max would help but raising the min might.
  5. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,236
    Location:
    Land of Cheese
    IF you have a bladder tank (not a standard galvanized tank) follow the instructions at the top of the forum for properly draining the tank and adjusting the air pressure. Make sure you have gauges that read accurately when you do so.
  6. masterpumpman

    masterpumpman New Member

    Messages:
    729
    Location:
    Virginia Beach, VA
    The screen on the pump could be partially plugged. I doubt that the well water level has changed enough to affect the flow! The pump seems to build enough pressure so the pump is probably OK. I still suspect a restriction in the pump screen.
  7. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    I had a similiar issue, and indeed the inlet screen on the submersible was packed with muck and gravel. However it was slow to pump to pressure even when all taps were shut. "suction restriction"

    Do a test of the pump by opening taps slowly when the pump is running and see how much it will flow and still "pump up" a bit of pressure.
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