I kept the Chlorine level at 15-23ppm for the first week. Until it held its level overnight for 2 days in a row and my test showed 0 combined chlorine. Then it took several days of not adding any bleach for it to drop back down to 8ppm. Do you think I stopped too soon? Yes running pump 24/7 and backwashing when the pressure rises. Is there such as thing as backwashing too much?