lost pump pressure

I have a sears 3/4 hp shallow well pump 390.2578 that I bought used on ****. I replaced an old pump with this pump. Sometimes I will use this pump on a shallow well and sometimes (currently) I use it to pump water from a spring holding tank (low positive inlet pressure)to my house. I need about 60 psi out of the pump to make everything work right. When I first got the pump it would easily go to 70 psi. I set the pressure switch to 40-60 and everything worked fine. I make a mistake and had sked 40 pvc on the out let side and vibration eventually broke the connection. I lost about 1,500 gallons of water and the pump ran dry for a while. I hooked everthing back up with steel pipe carefully and have no leaks. The pump will now only go up to 48-49 psi. I broke down the pump and everything looks ok. Hard to tell if clearences are off.
I have ordered new impeller and defuser and "O" rings.

In order to use the pump until new parts come I need to change pressure setting so that the pump comes on at 40 psi and off at 48 psi. I can't go much below 40 psi or the system that is in place won't work because of lost of pressure going up hill. I don't seem to be able bring the on/ off pressures closer that about 20 psi. I have backed off the small nut in the pressure switch all the way and am still left with about 32/48 psi.

I would appreciate any advice.

Thanks, singlewhip

Valveman

That is the minimum you will get between on and off with that type switch. Allen Bradley 836C7A Switch or Mercoid Switch will do it but need relay for power and neither is cheap.

lost pump pressure.

Thanks, valveman.
I got it up to 52/32 and it will now turn itself on and off. We will just wait for parts. My partner Patricia says, "Tell him the world is a better place because he's in it."

Thanks again, singlewhip