Help interpreting FAS-DPD FC/CC test results **Sorry, long, techy post**

[JimK]

....Adding DPD powder to my 10 ml pool water sample

I add 1-2 scoops of powder to get pink. I don't get an immediate pink nor a hot pink. I get a faint, light pink and while swirling the powder for several seconds, it gradually darkens a little bit. It does not reach the vibrant hot pink the way testing the shock this morning immediately did.

......

This part caught my attention. Are you adding 2 scoops of DPD powder to the water sample per Taylor's instructions? This part of you post sounds like you are adding 1 (incorrect) or 2 (correct) scoops.

I'm not sure why your sample would return to pink after turning clear. I've been using this test kit for years and it has never behaved that way. One possibility I just thought of is that it will return to pink if the DPD powder hadn't completely dissolved before adding the reagent (it will return to pink as the remaining powder dissolves).