I have a 1/2 hp water pump that pressure's to 28psi and keeps running without adding pressure.I turn off valve coming into the house to make sure water not leaking and still no added pressure.when I manually shut pump off it doesn't come on until I flick the switch?? When I run water psi goes to zero? any ideas

My familiarity with well systems and pumps has definitely has its limits, but if your pump is running and does not increase pressure it usually means that here is a leak in the line and the pump is trying to reach pressure but cannot. Look for any signs of leaking throughout or around the house.

When you have the valve to house turned off, and you then turn off the pump, does the pressure hold steady, or does it drop? If it drops, is it a slow drop or rapid?

Also, is your pump above ground or in the well? If it is above ground, how many pipes go into the well, one or two?

I'm having a similar issue. I have an above ground pump with two pipes coming in. I have replaced the blatter tank and pressure control. Also have added check valves on both inlet lines, and notice there is a check valve on the outlet pipe. Pressure builds to 25 psi. and does not get higher.