Fas/dpd vs color matching drop test

[LBI salt pool]

So today I used the color matching block for both my pool and hot tub. I was unable to tell if the colors were 2,3, or 4. Eyes play tricks just like the CYA test. Anyway I immediately did the FAS/DPD test and the results were 8 ppm in tub and 6 ppm in pool.
I can now see why I need to have the better test kit

 

[Donldson]

The yellow OTO test has its place. It shows if there is any chlorine/bromine in the water and cannot be bleached out no matter how high it is. And if you know what your FC is and see the color you can aim for the same color each time. But for any kind of precision at all the FAS-DPD test is the go-to.

 

[LBI salt pool]

If I was so cheap I wouldn’t worry about eating the reagent for the FAS-DPD TEST LOL
SO, according to my comparison today, the yellow OTO showed 2-3 ppm less than was it actually was. So now I know if I shoot for 5 ppm ( OTO test) it will be around 8 ppm actually
Thank you