I'll let Janet answer about her need for high chlorine for 3 weeks.

I just wanted to tell you that it will eventually work. I have no doubt that you are totally frustrated and I don't blame you for feeling like throwing in the towel. But, there is no other alternative. You just have to keep hitting it really hard with bleach. I know it seems it will never end but it will. We have had several people in this same situation this year and some of them have made it through to the other side. You will, too. So sorry this has been so hard but don't give up.