Pressure tank overpressurizing

I have an old (30 yr?) bladderless pressure tank on a shared (4 houses) well. It appears that over the last six months, air has been entering the tank somehow and ending up in the house water lines. I've been bleeding air out of the tank about once every week to ten days and that corrects the problem temporarily. My question is: is there any way (such as a particular pump failure mode) that would allow this to be happening, or is the only thing that could be wrong is that we are pumping the well faster than it can recover? (There's no obvious reason to think the water table has dropped in the last year.)
When I lived in New Hampshire (The Granite State), there was a process called "hydro-fracting" which involved dropping dry ice down the well shock cooling the bedrock and opening up the fissures to allow faster well recovery. I now live in Northern British Columbia (on probably clay and gravel), so my second question is: if we are overpumping the well, what can be done about it?
Thanks a lot for any information.
Denny
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Sounds like a bad check valve. The water is draining back down the pipe, and when the pump kicks on, it sucks up air first.

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Bob wrote:

Nope. If he has a jet pump or a shallow well one on top of the well and the check valve (footvalve) was bad, he would be loosing the prime. If it is a submersible, it pumps from under the water level and thus can't suck air from there. The only place I can see air entering the system at the pump location is from the snifter valve or a flapper valve on the side of the tank. Dissolved gases in the well water??
Harry K
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There's definitely nothing on the side of the pressure tank and no obvious places (clamps, etc.) where air could be leaking in. I suppose the drop line may be cracked, which would reinforce some suspicion that the problem coincided with the onset of cold weather--metal contracting and opening up the crack.
My best guess is that it's a submersible pump in a deep well (The story is that the original owner paid CA$10,000.00 in the '70's to have it drilled--but there's some speculation he may have inflated that figure to rip off the people he was going to share the well with. Nice guy.) As I said before, I wouldn't be surprised if this is a real "half-fast" system, just surprised it's lasted this long.
Thanks again, Denny
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If you don't have a pump above ground, and you have wires going down the well, then you have a submersible pump. Most likely the check valve is threaded to it. It's possible that the vertical pipe is cracked, but not probable. It would be spraying water out the crack when the pump is running. Can you look down the well and check that? It's more likely that you have a crack or pin hole in a section of pipe that is underground.

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Bob wrote:

It cannot be 'sucking' air in any section of pipe between the pump and the tank. That is all pressurized and any leak is going to spray out, not suck in. Same goes for any pipe on the delivery side of the tank. The only way air can be sucked into a system is from before the pump. My guess still remains as outgassing from the water or malfunctioning snifter/float valve in the tank.
Sorta OT. I was on a community well (originally 4 houses), It was down to 2 when I bought and somehow I wound up being an unpaid serviceman for the system. Got tired of that and drilled my own well. I have known others on community ones also and seems like all of them have complaints.
Harry K
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If a check valve at the pump is bad, and a check valve at the tank isn't, then any air hole between the two will allow the water to drain back down the pipe.

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Bob wrote:

Good point. I overlooked that the OP does have such a set-up. I really don't understand why it is done since it is redundant other than in one circumstance. A failure of the checkvalve at the pump, install one at the tank to obviate pulling the pump. Of course that does result in air in the pipes problems.
Harry K
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The check valve at the tank is so that house pressure does not put pressure on the well system when the pump is off. The check valve at the pump is to keep water in the well piping so you don't pump air every time the pump starts.

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Bob wrote:

<snip>
If you say so. I see no need to worry about "pressure in the well piping". There are a lot more items in the residence that will fail from pressure before anything in the well will. I have never seen a system with both check valves and have never worked on such a system which is why I overlooked to two valves.
Harry K
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If you have 40 or 60 psi pushing back on the pump every time it comes on, it will shorten the life of the pump.

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could be a bad check valve at the pump. when the pump is in the off cycle it will allow the water to drain back.the check valve at the tank will hold and the suction will allow air to be drawn in at the pitless adapter o ring . when the pump cuts on it will push any air that has entered into the tank. this is a very common problem with older systems that have a check valve at the tank.be carefull if you are going to attempt to pull the pump yourself as they can be very heavy in excess of 300 pounds. we have to retrive many pumps that customers have dropped. the cost of getting one out of a well that has fallen a 100-300 feet down the pipe will be greater than the repair would have been in the first place. the last one we did fell 325 feet and cost 1800 to retrive and another 1400 to replace the pump. but it was still cheaper than 10,500 for a new 1100 ft well. thanks and good luck. scott
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snipped-for-privacy@aol.com wrote:

That all makes sense except that I'm not sure this system has a pitless adapter (is that possible?) The water line comes vertically out the top of the well casing then through a ninety-deg elbow, through a checkvalve, then a couple more nineties, a stop valve, then to the pressure tank, etc. If there is a pitless in the system, can air really pass the o-ring? I think this is as simple (i.e. cheap) a system as was available in the '70's judging from the way the rest of the house was built. Thanks again for your help.
Denny
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if it doesnt have a pitless it could suck air at any clamps you could loosen a fitting after turning off the power and see if it sucks air scott
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