I read somewhere on this forum that if your chlorine level is high, your pH reading tends to be the same purplish color (appears to be 7.7 to me). My chlorine level on my pool is currently 17 (CYA is 160... been slowly trying to lower it). I added muriatic acid according to the pool calculator to lower the pH to 7.4, and the next day, still the same purplish color.
So I'm guessing the high chlorine level is affecting it. How can I test the pH accurately with a high chlorine level like mine? I've been using the TFTestKit.