Your pressure tank has lost most or all of it’s air. If the tank is a bladder style tank (pre-pressureized) the air charge should be 2 – 5 psi less than the cut in pressure. I.E. On a 40-60 pressure switch pre-charge air pressure should be 35-38 psi. This pressure should be checked with pump off and all water pressure relieved from the system. When putting air into tank drain valve must be left on to allow water to get out of tank. When all water is out of tank if air comes out of faucet/hose then bladder is bad and tank or bladder needs to be replaced. If you have a non bladder type tank then you would not pre charge tank with more than 10-15 psi.