I have a problem getting pressure to build up on my tank. The bladder tank has 30 PSI in it with the pump off and lines drained. I have a 1/2 horse submergable pump and it seems to pump fine. I shut the valve off to the house supply and the pump will not go past 30 psi. The pressure switch is a 30/50. It never builds up enough pressure to make the pump shut off. When I open the faucet at the tank to make the pressure drop it flows fine and then just dies. there is still flow from the pump but not enough pressure to build up to shut it off or hold it above 30.

Any ideas