Question on simple 2 drop test kits for PH & Chlorine

[mihzyd777]

Hello,

I know this is a silly question, but I've searched up and down and just want to be sure I have my info straight. With the simple PH & Chlorine test kits that you can buy from Walmart that are Chlorox brand, is the Chlorine test testing TOTAL CHLORINE, or is it testing Active Chlorine? I Believe it's total but want to be sure.
Thanks!

 

[Toxophilite]

Testing Free Chlorine (free available chlorine). Total Chlorine is your Free Chlorine + Combined Chlorine. Those test kits don't measure CC, which you need your Taylor kit for that. I know that the Clorox is OTO (yellow comparator block) which are pretty much useless in accuracy.

 

[JoyfulNoise]

OTO (yellow) only measures total chlorine.
DPD (pink) measures Free chlorine. It can measure total chlorine if you add an additional reagent to it.

However, if a swimming pool is properly cared for and when one actually has a clean and clear swimming pool, combined chlorine levels are so close to zero that it has almost no effect on color matching tests so, in that sense, TC = FC.

One more caveat though - the yellow OTO test is wildly imprecise. Even though there are color blocks for different levels of total chlorine, they are not very accurate. So TFP always treats the yellow OTO test as a simple "yeah, there's some chlorine in the water" go/no-go test.