I'm having a similar problem & would love to know more details. I've been dumping chlorine into my pool all week trying to maintain FC above .2ppm. I started with lithium shock, then went to bleach. We're having very hot sunny days, water temp is 91 degrees. On Wednesday night, per recommendations from my local pool store, I added 13 lbs. cal-hypo shock. According to the charts in my Taylor test kit book, this would raise FC to well over 30ppm in my 21000 gal pool. Thursday morning, FC was so high it wouldn't register on my Taylor K-2006 (so it was definitely over 20ppm). By Thursday late afternoon, the FC was 10ppm. On Friday late afternoon it was back to .2. Currently using tri-chlor tablets in an auto feeder and have a CYA of 90. BUT, the pool is absolutely gorgeous & clear with no signs of algae. Can't figure out what to do next???