I have a 24 foot round 4ft tall above ground pool with a vinyl liner. We just switched the filter media from ZeoBryte to sand 1 month ago and finally got the Chemicals right except the chlorine. I have added 11 pounds of powdered chlorine to the pool since Saturday not including the fact that the inline chlorinator is all the way open and working and I am still getting a chlorine reading of 0. Please help.