When testing my CYA level I usually pour the the test liquid back in the bottle and recheck it a few times and am pretty consistant about where I see the dot every time.
On 5/13 I tested my CYA level and found it to be around 22 ppm. I added 2 lbs 6 oz of 99% Trichlor (All were 1" except for one 3" tab) to a floater and let it all dissolve to raise my CYA since I wanted to get rid of the tabs. All the 1" tabs dissolved 9 days ago but the 3" tab was stubborn and finished dissolving 4 days ago. This should have raised my CYA level to around 32 ppm according to PoolMath. I tested my CYA level today and it was around 25 ppm.
Where did it go? What happened? There has been no rain here to speak of so I know it wasn't diluted by rain or me adding fill water. The tabs did add FC but I couldnt say they added what they were supposed to.