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?

But then I read that the FAS-DPD is for high clorine readings.

So my confusion is that if you have to shock your pool to a theoretical 25ppm, what do you use to measure it?

(this may be a totally stupid question, and if my pool was ready and I had the tests- it might make more sense)