PH in my dad's pool is very low, color is lighter than the 6.8 low end of the scale. I want to adjust it up tonight so tried to test alk so I could determine if I should use baking soda or borax and how much of which to get, but the HTH drop test won't work. The 5 drops I put in the 25ml sample are supposed to turn the water green, then you count drops of the titrant until it turns red. Problem is the 5 drops turn the water a dark pink. I tested it with tap water to make sure the indicator just hadn't gone bad, and it worked fine, also worked just fine in my pool a few weeks ago.
I seem to recall certain circumstances where the ALK test won't work, but can't find them now. His CYA is sky high, my guesstimate is 150ppm. Is it the high CYA or low PH that's preventing the test from working?