You don't need to replace the sand. I think I am on my 10th season with the same sand. Poconos and CarlD also have the same sand that they have used for at least that long. Not sure about Aylad. At any rate, I think your sand is probably fine.

Can you post a total set of your other numbers? This thread is getting pretty long. I'm sure you gave us all the numbers before, but we are now on the second page of this thread and it is difficult to have to look back so far. Give us current alk, cya, calcium hardness and pH again please.

At this point, are you adding anything other than bleach? Are you running your pump 24/7?

Take a look at this link:
http://www.poolsolutions.com/gd/100-...ool-water.html