I have a deep well and a new pump. My low end shut off is at 20 psi. what if will happen if the pressure in the tank is too high?

In theory, the tank could explode. Most systems have a pressure relief valve to prevent pressures that high. But most tanks are rated to 100# or more, and it's hard to imagine pressure building much higher than that.

Certainly having your pump kick off at 60# would be no problem at all.

What is the high end shut off pressure set at?

Also. To add to jlisenbes post if you set the PSI in the bladder tank too high the back pressure will prevent the membrane from stretching to allow water to enter the tank. Your pump would kick on every time you made a draw. Good luck, Tom

Would this then reduce the pressure through the lines?

It does kick off at 50 this is the highest setting I can get

Would this then reduce the pressure through the lines? No! Increasing the tank pressure to the point that's over the pumps cut out PSI will prevent the membrane from stretching to allow water to enter the tank. It would be like no tank was there at all and Your pump would kick on every time you made a draw.

It does kick off at 50 this is the highest setting I can get You have a 30/50 PSI control box. This is a factory setting. It can be adjusted up or down in the control box. Isn't 50PSI enough for you? If not then how old is your house and what material are the water pipes? Back to you, Tom

There are two ways of adjusting pressure in the tank. The first is referenced by Speedball's really good drawing above. That is adjusted by adding/removing air from the little air valve at the top of the tank. That is to be done with the system off and the tank emptied of water by opeing a low level spigot until no more water comes out. Set that pressure at 2# below the point where the pump turns on. In your current case, that would be 18# if the cuton point is, as you said above, 20#.

The other way is to adjust system pressure, meaning the points at which the pump turns on and then off. That is done at the pressure switch. Now this is where you have confused me a bit. You said the pump cuts on at 20 and off at 50. That is strange. There is usually a 20 pound difference between the two. At any rate, you can increase them both by turning the large center nut on your pressure switch. Turn it clockwise (with the breaker off) a couple of turns. Turn the power back on and see what your cuton/out points are. Continue to adjust until you get want you want. But if you have a 20/40 switch, it might be tough to get it up to 40/60.

Here is the problem you will run into. When you set the cutoff for your switch at, say, 50#, then 50# is the BEST you will get, and the pressure stops dropping as soon as you start drawing water. It drops fairly quickly, and so you end up with something in the 30# to 40# range for most of the draw. That's why it can be nice to use 60#as the top end. That way, you will end up with 40# to 50# most of the time.