I just put on a new switch and adjusted it to 30 cutin and 50 cutout like it says to do and when it shuts off, why doesn't it hold pressure until I run water? It loses pressure as soon as the swith and pump shut off.

How deep is well? If u are losing pressure and u don't hear water running it is probably the check valve in the well.

Chuck

If you have a cutoff valve to the house, then close that and see if your problem goes away. If it does, then there is a leak somewhere in the house. If it does not go away, then suspect the checkvalve. Is your pump in the well or above ground?