I have an inground, 21,000 vinyl liner with sand filter. water is clear but i'm having trouble getting the clorine to hold. i use a taylor 2006 kit, just got my new reageants in. my results are cya apparently is zero....the black dot does not disappear after using all the solution. Clorine 0, ph 7.0, TA 100 and calcium hardness is 40. I do drain my below below the skimmer in the winter, so i do have to add water, which i use my filtered well water to add. I have been adding bleach for the past week, keeping it high(not sure as to the number since i didnt have any reageants and was only using the oto kit from walmart that only checks clorine and ph) at the start it was slightly cloudy in the deep end. but now it is clear, just cannot get the clorine to hold. please advise