Yes, so true, that's the option to fall back on. This said, I did check it last night and the ppm's holding at 4.5. I'll check again soon, and expect it to be the same. I *really* do think this was a case of old chlorine now. As always, thanks Janet for your advice. I'll wrap this up with one more post next Monday and hopefully will report 4.5 once again. And now, "sleep, pool, sleep...and sweet dreams along the way."