I know this topic has been covered but it seems my situation is unique so any help would be appreciated. The issue is simple, the pressure tank only partially fills, maybe a gallon or two, I can move the tank with my pinky finger, but here's the thing....if I turn the pump off and turn the water off and then drain the tank it will fill up properly when I turn everything back on again, but once the level goes down during it's first use it will only partially fill after that. The tank is a bladder type and about 2 years old, the pump is set at 30/50 and cuts in and out at those settings, I've removed the house filter to eliminate a filter problem, the tank pressure when empty is at 28psi, there is no real problem with water pressure although it does vary while showering, the pump is not short cycling. Any ideas why the tank won't fill??