I just filled my pool a few days ago. I decided to SLAM it as I had a bit of algae at the end of last season when I put away my pool (9x 18 above ground pool). I had no problems for most of last year; however, this time I can not get it to hold Chlorine. I got absolutely no reading for CYA. I thought perhaps my chemicals were old or got wet in the garage, so I purchased replacement. The first time I slammed, the FC was only 7, rather than my target of 10. SLAMMED again the next night, and it was down a bit, but thought it might be OK. I just checked this evening, and I have absolutely no chlorine! I did use a Safeway brand of bleach - could that be a problem? I used Clorox tonight. I will check again in the morning and monitor it throughout the day. I have never had such a problem before.