I have a well/pressure tank system which is showing most of the signs of a bad pressure tank (very short cycling), BUT with a big difference. When I try to drain the tank (with the power off and the valve to the house closed), there is a spurt of water, then the pressure gauge drops to zero and the flow stops completely. The pressure in the tank is still mid to high 40's (measured with an air gauge on the tank), but nothing comes out of the valve. If I turn the pump back on at this point, it runs momentarily, the pressure gauge returns to just under 50, and the pump shuts off again.
If I try the same procedure with the valve to the house left open, the water will run for longer, then the gauge will drop to zero and the flow will stop. I think the longer flow is because water is draining back from the pipes. When I turn the breaker back on, the pump will run for a few seconds (maybe 10) until the pressure gauge reaches 50, then shut off. I think it runs longer in this case because it is re-pressurizing the house plumbing.
I think what all this means is that something has blocked the flow between the pressure tank and the valve and pressure switch. Can anyone see a different explanation?
If this is the case, it means I can't release the pressure in the tank, so I can't drain it. Trying to replace it while under pressure would be a real nightmare. Any suggestions?