I'm in the process of opening my pool, although the current weather indicates that the swimming pool season wouldn't start until mid July
Obviously, the first two values we check are pH and CYA.
The pH was high so I lowered it to 7.2.
For CYA I used the Taylor kit and the TF Test Kits. I like the TFT for CYA because it can measure lower values up to 20 while the Taylor stops at 40. Both kits were about 2-3 years old and during the off season they were kept in the fridge.
Here are the results:
two different dip strips - close to zero.
pool supply store: 9
Taylor - at 40 I could still see the black dot.
It's hard to believe that four are wrong and only one is right.
So I went with 9 ppm.
I just wonder what happened to the reagent of the TFT Kit.