Recently I replaced the relay switch to my pump. When I did that the pressure in the tank would not reach over ten pounds of pressure. About 3 days later it stopped building ANY pressure. It had no prime. Ive put enough water that it backs out imperrior cage. Yet it still will not build pressure. It seems to be primed and holding water. Any advise?

By "relay switch" do you mean control box? Why was it replaced? What setting is it? What's the bladder tank charged at? If it holds prime then is the impeller turning? Are you sucking air? What type of pump? How deep the well? Back to you, bTom

By "relay switch" do you mean control box? Why was it replaced? What setting is it? What's the bladder tank charged at? If it holds prime then is the impeller turning? Are you sucking air? What type of pump? How deep the well? back to you, bTom

Control box. The connections were bad. I believe 30-50. Not sure, how do I check the bladder charge. Where is the impeller located? After I get it primed I turn the pump back on it holds prime and if I open the faucet head located directly above the pump a slow stream of water eases out. As soon as I turn the pump off again yes it sucks air and the water and prime is gone. Not sure on the type of pump other than its under ground. Im pretty sure it's a shallow well it takes approximately 2 gallons to fill it with water to the tank.

Sounds like dirt in the foot valve or a bad foot valve.

If your pump's a submersible then it's self primimg.

how do I check the bladder charge. Turn the pump off and open a cold water tap to relieve the pressure. Check the charge at the air valve on top of the tank. The charge should be 2 PSI under the cut in point on the control box.

Where is the impeller located? The impeller cage is located just forward of the pumps motor.

As soon as I turn the pump off again yes it sucks air and the water and prime is gone. This could be caused by a falling water table, Have the water level in the well checked. You may have to lower the pump or dig the well deeper. Good luck, Tom