Re: Which test kit?

Originally Posted by
iwannapool
How often would I see CL, CC or FC, above 15 ppm? I guess if you get a big problem CC could go high, but FC? By the way, what is FAS-DPD; is it an acronym or ?
DPD and FAS-DPD are the reagents used.
DPD is N,N-diethyl-paraphenylenediamine. It is the indicator used to test for clorine (and other halogens) using a color comparator. Most men have difficulties with this test because they cannot differentiate between the shades of red the test produces. The test can bleach out at chlorine levels above 10 ppm (which is not even shock level in most pools!). It is accurate to 1 ppm (IF you can differentiate the different shades of red produced.) It can test both free and total chlorine so combined chlorine can be found by the formula TC-FC=CC
FAS-DPD stands for Ferric Ammonium Sulfate -- N,N-diethyl-paraphenylenediamine
This test does not use a color comparator but is a titration test (like the tests for Total Alkallinity and Calcium Hardness) with a distinct endpoint color change from bright pink to colorless. Even people who are colorblind find this test easy to do. This test will not bleach out at chlorine levels as high as 50 ppm with an precision of as much as .2 ppm. (Comes in handy when you want to try and kill algae and it requires you to keep your FC levels at 15 or 20 ppm!) It test for free chlorine and combined chlorine directly. If you want to know your total chlorine it would be FC+CC=TC.
All things considered the FAS-DPD test is much easier to do and produces much more accurate results and is worth every penny extra it costs!
Retired pool store and commercial pool maintenance guy.
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