In refurbing my well water system, I find what looks like a vacuum switch connecten between the pump and the water tank. What is it and what does it do? I primed the lines after replacing the foot valve but I could not get water into the holding tank. Is the vacuum thing the problem? Or is something else wrong?

I see "water tank,. I see "holding tank. Now tell ne what you have, A bladder tank? A pressure tank or a holding tank? How big is the line? Describe the "vacume switch".
Does it have wires going to it? You pulled the well point to change out the foot valve. If it jammed in the open position why not simply install a check valve on the surface? Back to you Tom.