Highest FC for testing

[S Ray]

Hi all
Just shocked pool, how high can FC be and still have accuarate test results. I think I read its different for different tests.
Thanks, Steve

 

[PaulR]

Depends on the type of test. The OTO test (drops that turn yellow) generally comes with a color block that goes up to 5; you can dilute your sample half-and-half with chlorine-free water to double the range. The DPD test (drops that turn red) I think works the same way, range-wise; although it tends to "bleach out" at high FC levels (incorrectly reads very low). The FAS-DPD test (powder that turns the water pink, with drops that make the color go away) is supposed to work up to 50ppm.
--paulr

 

[S Ray]

Hi again,
What I ment to say was Id like to run all the tests. Will different tests require different FC levels.
Thanks,Steve

 

[PaulR]

Ah, okay... the pH test starts being unreliable at FC > 10; I hear that high FC can also cause the, uh, I think it's the TA test to turn unusual colors, but if you're just looking for the color to start and stop changing, the exact color isn't important. I don't think anything else cares about FC level.
--paulr