I have what I believe to be extremely high CYA. I tested using a Taylor (#2006) FAS-DPD kit. Reading was off the scale. I then mix one part pool water to to one part tap and retested. Still off the scale. I then decided to mix one part pool water to FOUR parts tap water and retested. I now get a reading of approximately 42. My question(s) are, should I multiply the 42 by 4 to get a total of 168 or am I multiplying 42 by 5 for a reading of 210? I know in either case that I will be dumping pool water this afternoon and refilling to get this under control. My thought is start with half the pool water. Does that sound too extreme? I really don't want to pull too much out only to have to replenish.