Tft100 vS hach pocket colorimeter II

[lindsaygib]

That's a pretty close match. My best suggestion is still to trust that TF Pro FAS/DPD test. It's sorta' the gold standard

Thank you!

 

[lindsaygib]

0.4ppm. It’s a low end measurement so you’re not that far off. And you need to be really accurate with your water sample size.

I would be more inclined to believe the colorimeter is not acting linear on the higher end. Colorimeters are usually only linear over a fixed range. We have seen no end of problems with digital testers and water analysis. Trust the chemistry and not the colors …

Thank you! I just diluted the pool water and the readings were the same. It does seem to be an issue with only the higher readings.