Late last year we started getting water pressure surges in the house. If you were taking a shower there would be increased pressure as the pump turned on. This would happen every 20-30 seconds.
I checked the pressure tank and it was holding pressure best I could tell. Maybe I got a bit of water out of the valve when I checked the pressure. Hmmm, said I. I ended up changing the pressure switch which did help. For a month or two. Then the problem returned.
I went back and checked the pressure tank again. Ours is a bladder tank with an air valve on top of the tank. I checked the pressure but this time water shot into my pressure gauge.
We called the plumber. :laughing:
In THEORY we could replace the bladder in the tank. The problem was I could not find an online supplier nearby, the ones I did find wanted almost as much for the bladder as a new tank, and the suppliers were in China.

Did I mention we called the plumber? This is why.
He installed a metal pressure tank. WellXtroll is sounding familiar. The plumber, who is a good guy, said we should not have any problems with that tank. The tank the well driller installed was a wound fiberglass tank. I figured that would be ok since it will not rust. I read, or my plumber said, that those tanks do not last.
I certainly do not know if that is true for all tanks but ours lasted six years and I would not buy that brand again because what should have been a cheap, fast, fix was not cheap or fast.
If you get water out of the pressure valve on top of the tank ye have a problem. You should be able to search and find the instructions for your tank on the Internet. The amount of pressure you have in the tank depends on your pressure switch. Different switches support different on/off pressures. You need to know the pressure cut on/off for your switch to help diagnose the problem.
We paid about $450 for a new 5ish gallon pressure tank. Installed.
Later,
Dan