You cannot test high Cl levels accurately with that OTO test. You need to get the FAS/DPD test out of your kit and use it. There is no other satisfactory way. The OTO is for testing levels of 5 or less and the dilution method is an inaccurate stop gap, at best. Also, if you are dosing accurately, you have no need to test more than once each day...simply testing for consumption...not to see if you put in enough Cl.