We have a large farm with two wells. 3 days ago we had no water in one barn so I checked the breaker to the well pump it was off and tripped every time I turned it back on. So I opened a valve to connect to the other well to get us buy. The next day we pulled the well pump and replaced it the control box, and the pressure switch since it has not been replaced for 12 years. everything worked great for a couple days than the pump started cycling on and off very rapidly every second. Called the plumber he put on a new pressure switch. Still same problem. He is dumbfounded and so am I. We do not have a leak in the well line because when we shut the valve off coming out of the main pressure tank the pressure holds. The pressure tank is only 2 years old and is operating properly. Also there are 5 other large pressure tanks on this well at needed locations around the facility. But the well line feeds into this many one first. Does anyone have any ideas. We use allot of water prob ally over 15000 gallons a day and we need to get this well back into service . Thanks in advance