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Thread: Fluctuating pressure shallow pump

  1. #1

    Default Fluctuating pressure shallow pump

    I have a seasonal cabin with a shallow 1/2 hp jet pump sitting piggy back on a horizontal bladder tank 1 year old.
    The water pressure seems fine until the pump turns on, when in the shower at that point, the hot & cold starts coming in alternately rather than mixed warm.
    I've watched where the pump kicks in a few times, but hadn't noticed where it kicks off, but just before I left yesterday, I think I noticed the pump kick in at around 30#, but then drop immediately to around 5# and start to build from there, and bouncing by about 20# when in the 15-25# range (rapidly fluctuating between say 15 & 35# while gradually increasing overall) until it gets up above around 35#, then the pressure begins to steadily build until it shuts down just shy of 50#. The system holds the pressure fine, and I don't believe it's cycling when no water is being used. Unfortunately, I won't be able to confirm that it dropped immediately after kicking in until the next time I'm there, and I'd like to have whatever I need to fix it with me when I get there.
    So, is my pump somehow letting the pressure blow back down the well when it first starts up, or what else could the problem be? I don't know much about pumps & wells, but that seems the only logical answer, but why would it hold pressure until it runs?
    And finally, if that is the problem, do I repair the pump(with what?), or replace it?

    Obviously my first time post, thank you very much for any insight!

    Mike

  2. #2
    Previous member
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    Jul 2005
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    Riverview, Fl.
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    It sounds like your bladder tank is out of whack pressure wise and the pump is cavitating meaning it can't get water as fast as it would like. Beyond that, I can't help much without a lot more info.

    bob...

  3. #3
    Rancher
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    Quote Originally Posted by Floaten
    I've watched where the pump kicks in a few times, but hadn't noticed where it kicks off, but just before I left yesterday, I think I noticed the pump kick in at around 30#, but then drop immediately to around 5# and start to build from there, and bouncing by about 20# when in the 15-25# range (rapidly fluctuating between say 15 & 35# while gradually increasing overall) until it gets up above around 35#, then the pressure begins to steadily build until it shuts down just shy of 50#.
    OK this is an indication that the pressure inside the bladder tank is too high, if your water pressure suddenly drops to zero it means the tank is empty of water, turn off the power, drain the water tank, measure the pressure in the tank, set it for 2 psi less than you cut on pressure of the switch. And you should be good to go. Report back here if that helps.

    Rancher

  4. #4
    Moderator valveman's Avatar
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    Mar 2006
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    Lubbock, Texas
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    Your pump is coming on at 30 and then dropping to 5. If the pressure drops AFTER the pump starts, then it is losing prime and takes some time get the flow going again. I think your bladder tank is fine and you have a suction or foot valve leak.

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