I have a ba cu 301.

I have a bad cu 301. I read a post about changing the system out to the old style presure switch. I have a 10 gpm in the well and 15 gpm in an above ground tank. The above ground has the cu 301 and the 10 gpm uses an old style presure switch. I do not know what the csv is that was mentiond in the post about the conversion. Can someone please tell me what a csv is? Also can I use my large 80 gal bladder tanks if I convert or do I need a small 2 gal bladder tank for the switch?

CSV = cycle stop valve. Go on the pumps and wells forum and use the search function...you'll be able to read a lot about them. My take is that you could use your existing large bladder tank, but normally wouldn't need a large one if your well and pump can keep up with your maximum demand. When it dies, you could save some money and replace it with a smaller tank with a csv installed. You probably won't get the benefit of the more constant pressure a csv can provide with a larger tank, as the tank would have to partially empty before the pump would come on and the constant pressure would then be held (as long as you can keep up with the usage).