Tf-100 Free Chlorine testing question

catdrugn

LifeTime Supporter
Apr 4, 2008
19
This old man needs a little more advice. This time on testing FC. I think I'm doing everything correctly but I'm not getting the expected results.

I fill the tube to 10 ml and add a heaping scoop of the powder and swirl. The water turns pink with the addition of the powder but during the second or two of swirling the water turns sorta milky white. And this is before I add any drops. When I begin adding the drops the water stays milky (or cloudy) then within about 15 drops or so starts turning pink again and stays that way, even up to 40 drops.

What am I doing wrong? And am I looking for the water to go from pink to white (milky, cloudy) or should it go from pink to clear (see through)?

Other info: The water is crystal clear. PH is 7.2. CYA is still high @ over 100.
 

duraleigh

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Apr 1, 2007
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Sebring, Florida
Wow! That's puzzling? What results do you get when you do the OTO test for chlorine? (that's in the blue plastic box with the comparator that tests both FC and pH)
 

catdrugn

LifeTime Supporter
Apr 4, 2008
19
Hi Dave,

The basic test kit shows a dark orange color for the chlorine and shows 7.2 - 7.5 for PH.

I double checked the bottle numbers I was using: the R-0870 DPD powder and the R-0871 chlorine test liquid for the FC test.
 
G

Guest

Sounds like you have very high chlorine levels and the DPD is bleaching out (the dark orange color on the OTO test confirms this!). Add another 1/2 scoop to 1 scoop of DPD powder until the pink color is holding (it might even take up to 2 of 3 scoops extra) and then titrate. 40 drops would be 20 ppm and it is very possible that you are higher than that. As an alternative, try mixing equal parts of pool water and distilled water and testing 10 ml of that. Count each drop of titrant as 1 ppm chlorine.
 

duraleigh

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Apr 1, 2007
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Hi, Evan,

Thanks! I hope that's the case. I am puzzled by it, tho. I have tested FC up in the 40's (not my pool....thank you very much! :lol: :lol: ) and the sample never turned white.
 
G

Guest

Cloudiness CAN happen when you add the DPD powder. Not sure what causes it (probably some of the propriatary buffers that Taylor includes in the mix) but it has no impact on the results. You want it to turn from pink to not pink. It might be clear or it might be cloudy. Mine is usually cloudy :cry: :shock: . The fact that it turned pink at all and then not pink indicated bleachout of the DPD.
 

catdrugn

LifeTime Supporter
Apr 4, 2008
19
Your theory sounded good to me waterbear. I added 2 scoops of the powder and the pink color held. I commenced to adding drops. I got up to 100 drops before deciding the pink just wasn't going away. I must have a major overdose of C. As a side note my brown golden retriever took a swim and is now white......coincidence? :)))

I'm going to wait a few days (or a month...) and let the C levels come down and test again.

Any other suggestions, let 'em fly!
 

derek1027

Member
Apr 30, 2008
10
I added the drops and got the color change from pink to clear with 8 drops (so 4ppm). While reading the directions for performing the next test, the solution changed back to a very light pink color. Should i add another drop or 2 to get it to remain clear longer and count that into the FC ppm? It was staying clear for probably 20-30 sec then changing slightly (I was holding over a white sink so change is very obvious)