Okay. I put in too much Dichlor over time using the "Vermont/Norhtman" method (as recommended by the person who sold me my spa) and plan to drain my water since my CYA is around 150 ppm. I've learned my lesson. Until I replace my water, however, TFP recommends a level of 11 to 18 ppm FC which is what would normally be a shock level at 20 CYA levels! Am I in danger of "bleaching" myself or being overcome by Cl2 gas at these levels (18 ppm or greater)? Put another way, my test strips read over 10 PPM FC; doesn't CYA "buffer" the Cl, so the effective readings should show lower levels anyway? Or do the FC readings from my chem tests some how "ignore" the binding of Cl to the CYA. It seems to me if, if I'm reading 10 ppm of FC, then that is 10 ppm of FC, regardless of CYA levels, including effectiveness.
Thanks for all the great help! Your web site is one of the few that seems to be consistent and in line with my background in chemistry and engineering.