High PH - Feeling stupid

[waterbear]

CarlD:

I think I am confused in general on testing kits for clorine. I keep reading that Ben's test kit is only accurate up to 15ppm and it is a FAS-DPD test isn't it? (I don't have it so I don't know). Above 15ppm - doesn't it start to bleach the reagent so you can't read it? The OTO clorine test doesn't bleach - but it only reads up to 5ppm?
The DPD drop test (such as the one in the Taylor K-2005 kit) for FC/TC can bleach out. It is not the same as the FAS-DPD titration test that is in Ben's kit.
But then I read that the FAS-DPD is for high clorine readings.
Correct. (or you can use OTO with dilution of the sample but it will only measure total chlorine)
So my confusion is that if you have to shock your pool to a theoretical 25ppm, what do you use to measure it?
FAS-DPD
(this may be a totally stupid question, and if my pool was ready and I had the tests- it might make more sense)

Hope ths clears things up.