I have been testing my water myself for the first time this year thanks to this forum, but I still get my water checked periodically at the local pool store if I am going near it.
My test results and theirs seem to be fairly close except TA where they always show me lower than I show. For example yesterday I show TA=170 and they show TA=129. Prior tests have been about the same with the pool store about 40 less than my result. These are all done around the same time and with the same water sample.
So my question is if I am reading the test wrong. For example, the above test of 170 was green until about the 15th drop when it turns kind of green/purple, then on the 16th drop it may be more of a very dark purple, then on the 17th it goes more of a red / pink. So I am calling that 170.
Is the correct method to count until red, or count until not green?