You'll probably never "keep" 8PPM chlorine. Under normal circumstances, it gets used up daily by UV exposure and general pool maintenance. The thing to learn is how much you lose per day under normal conditions. Once you've kept it steady for a few days, you'll start to see how much you have to add each day to keep it within your targeted range. Once you have that, pool maintenance is super simple. Add your X qts, X cups, whaterever, every night (do it at night!), and it'll be crystal clear.