esWell pressure SOMETIMES go down with house shut off?

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We sleep one floor above our well pressure tank. Last night my wife awakens me from sleep to inform me that the well pump keeps coming on. I spring to life, get down to the basement and start troubleshooting. This is what I found:
With the valve after the well tank turned off, house gets no water, I watch the pressure gauge and sure enough it goes down, about 20 psi in two minutes. Pump kicks in, tank reaches cut off pressure and again pressure goes down. So I shut off the electric to the pump and go and Google well pumps and check valves.
I go back and run the pump and watch the gauge, sometimes the pressure does not drop, the pressure holds!
What we have:
Pump down at about 180 feet, water at about 60 feet down, 1/2 horsepower pump, 220 volts, 82 gal Flotec bladder type well tank, check valve at well tank, not sure if there is check valve at bottom of well, well pump at least 10 years old, Home Depot well tank check valve 7 years old.
My thoughts: check valve sometimes works and some times does not %^), does that happen? Did I leave out important clues?
Is there a way to know, or can I do some test to determine if I have a check valve in the bottom of the well? If I do does this mean that one check valve is bad and one check valve sometimes is bad?
Cheap fix, replace check valve at well tank? Is cheap fix a bad idea or does it buy me time?
Thank you for any help.
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Typo in subject line, sorry. Subject should read:
Well pressure SOMETIMES go down with house shut off?
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valve down at the pump. Otherwise it would draw a vacuum whenever the pump was not on.
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If a submersible...which it must be at that head, it will not draw a vacuum.
AFAIK all submersibles have a built in checkvalve. People do install a second one at the tank but it is either redundant or put there because the pump one failed.
Harry K
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.
I put one in at my tank when I had a similar issue, the guy who ended up repairing my similar issue for me told me that in MI they are illegal at the top of the well, can't remember why anymore, I took it out as once the issue was fixed I didn't need it anymore... In my case the problem was very similar to your issue andy, the pump ran, but, when it went off, the water seemed to be draining back down into the well. Turns out for me it was the saddle that connects the well caseing to the line leading into the house. after about a week of the issue water started to run up the casing and pool in the yard. I had a guy come and dig down to the saddle ( about 6 feet down, ) and replace it... all set now. $ 1,300 later.
good luck,
Dave
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If it's submersible, that will keep air from getting into the pipe, but doesn't change that fact that it will draw a vacuum if the water level is more than 34 feet below ground without a check valve at the pump (or a bad one). The water column weighs more than the atmosperic pressure acting on the cross section. (Of course, it won't be a true vacuum but a column of low pressure water vapor above 34 feet.)
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The pump is buried in the water at all times. It cannot "draw a vacuum" unless the well is pumped dry first. Could a vacuum form after the pump shuts off? Yes, if the checkvalve leaks. That has no effect what so ever on the operation of a submersible pump.
Harry K
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"If a submersible...which it must be at that head, it will not draw a vacuum."
The vacuum would be between the check valve at the tank and the pump. The pump would push water through the check valve. When it shuts off, a vacuum would be drawn behind the check valve to about 30 feet above the water level. Obviously there would be no vacuum in front of the pump.
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.
And would have abzero effect on pump operation. The 'draw a vacuum' bit implies "while the pump is running (or trying to)". Drawing a vacuum as far as operation is concerned is only in effect on a top of the well (shallow well, or jet) pump.
Harry K
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If you stopped reading halfway through the sentence I can understand that interpretation, but the entire sentence was, "Otherwise it would draw a vacuum whenever the pump was not on." Clearly he meant that gravity would create a vacuum in the pipe as the water backed up past the pump at the bottom.

That is clearly what he was describing, which is why we were all baffled as to why YOU said it would not happen if it was submersible...
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I am still wondering why he even made the post considering that it has zero effect on system or pump operation. I have never seen the situation described as "drawing" a vacuum. That, as I said, implies the PUMP is doing it no matter what he added to it. Again. Why even post about it as it is totally immaterial to begin with?
Harry K
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I agree. Found Larry's post most confusing. Also not familiar with the term "Drawing a vacuum". Apparently it might mean that if/when water drained back down due what is most likely a defective or debris encrusted 'foot valve' at or below the submerged/submersible pump, then the water in the tank might get pushed back down the pipe, by the built up pressure behind the bladder, (we have never had a bladder equipped tank). Then when the pressure dropped below cut-in setting of pressure switch, the pump would cut in, again, and pump up to cut-out pressure. Hence the pump cycling. Where 'drawing a vacuum' might' come in is when a pump is at ground level, no more than about 25 feet (one barometric pressure) above the water level? Not in this case? Harry; you think I've got that right?????
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Mostly. In the given case with a good checkvalve at the tank and a leaking one at the pump, when the pump shuts off there would be a vacuum formed in the down pipe. Has no effect on operation however and his mentioning it was pretty much pointless.
I will admit that I missed the 'when pump shuts off' bit but it still has no bearing on my comments.
Harry K
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With no, or a defective check valve at the pump and the water level 60 feet below ground, the upper 26 feet of the pipe are going to be a virtual vacuum (empty) when the pump is off. That means that when the pump comes on, it will take time and wasted energy for the water to rise that 26 feet before it starts supplying pressure to the system. It might also hammer the pressure tank when it gets there, but with 1/2hp pump, I'm assuming that's not a big problem.

Neither have I. I just thought it was fairly obvious what he meant. But then I may know more about barometers than I do about submersible well pumps, so I had the advantage of having to actually tink about what he wrote rather than assuming I already knew...
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Harry, so I don't sound like too much of a jerk, I started my last post before your last one showed up at my server...
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Stormin Mormon wrote:

You've never heard of top posting either? *snicker*
TDD
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If you have a schroder valve on the top of your pressure tank , push it if water comes out then you need a new tank. as water pressure is not held by the check valves just water is , remember the tank air is 2lbs less then the turnoff pressure you have the pump set at 30-50 air in tank 28 pounds . Check it first
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Or just add more air into the tank...it will have to be done regualarly though. It is also not recommended as a blown diaphragm can trap stagnant water that can contaminate the good stuff.
That 2psi seems to be the standard although some tanks (mine inculded) say 'the same as cut-on (mine is at 2psi below). Somehow I can't wrap my mind around how the pump wouild ever cut in with that much pressure already in the tank.
Harry K
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Well...I suppose it would cause a bit of an excess expense but it would be rather hard to measure. I don't see the "hammer" problem as there is (or should be) an air bubble in the tank to absorb it. Without thebubble you will get a very bad hammer repeatedly untill you shut the pump off - BTDT with a pretty well worn out shallwell pump. Doesn't have anything ot do with a vacuum though, just proof that you can't compress a liquid...at least in real world pressure systmes. Sure does give one a clue as to the cause of the problem! :)

Harry K
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