Just opened my pool over the weekend. I added bleach early evening yesterday. It hadn't had anything added to the water since late October although the water was crystal clear when I pulled off the winter cover. I put enough bleach to take it up to 14 FC figuring that there would be junk that needed killed even if I didn't see anything. I went out early this morning before the sun was up and it is still reading 14 FC. Could it really be that there was nothing in the water to use up any chlorine after sitting untreated all those months???