I have read here that a free chlorine level above 10ppm will render your pH test inaccurate. I usually test for chlorine and pH twice daily. I add 8.25% Clorox in the evening, shooting for 7.5 to 8.0 ppm. I have noticed that when I test in the morning (when the free chlorine is 7.5 to 8.0 ppm) the pH will be near 7.8. However, when I test in the evening (when the free chlorine is 4.5 to 5 ppm) the pH is usually nearer 7.5. Does a higher free chlorine level actually bring the pH up or is the test not accurate when the free chlorine level is in the 7.5-8.0 ppm range? My pool has been perfectly clear and algae free this year using TFP techniques, thank you!
pH 7.8, fc 7.5, cc .5, ch 100, TA 80, CYA 40