Pressure lasts 3 minutes!

My well's driving me nuts! I have a 3 acre parcel on one well. The well has a 250 gallon pressure tank, which, when sitting, shows approximately 50 lbs pressure. Once I turn on any single hose or sprinkler, I have a wonderful "teaser" pressure for about 3 minutes, then pressure drops to approximately 20 lbs. My well pump then runs constantly, but never "repressurizes" the system until the hose is turned off.

As I run my hand up the metal surface of the tank, it feels like the water level is below the float...the side is only cool for about 2 feet, and my tank is nearly 8 feet tall. So I'm thinking I may have 6 feet of air in the tank? There is a little snifter valve which is supposed to add (or expel?) air, to keep the proper air/water ratio, but I never hear it making noise. Upon inspection, no spiders, earwigs, etc...in that valve.

I've called our well guy out once every other year for a related problem, and he never manages to do anything but replace a few components and bill me for the trip! The problem persists!

Any help or advice would be appreciated!

Ty

Tanks don’t make pressure, pumps do. Once the pump is started, it sees the tank as another load, and has to fill the tank at the same time you are using water elsewhere. The pump should give you the volume and pressure you need, even if there was not tank in the system. Either your pump is not large enough to supply the volume and pressure you need, or the well will not produce enough water, or both. The tank has nothing to do with that part.

hmmn

Hmmn...I've lived here 12 years, and we're on the same pump we've always been on. I would think a pump either works or doesn't...right? If it quits, it will fully quit. So...this leaves a water issue as the likely culprit?

You could have a restriction in the system such as a plugged inlet screen or failing check valve. It's also possible that there is more than one check valve and you have a water leak below the water line in the well. There is no easy way to completely test for this unless you are prepared to pull the pump.