Confused with Chlorine test results OTO vs DPD

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Killer95Stang

Killer95Stang

Well-known member
Aug 17, 2012
977
Sunny SoCal
So.. I've been a proud owner of a Trouble Free pool for the last two months. I have religiously tested for Chlorine levels and PH on a daily basis. I then test everything else using my TF-100 kit with Speedstir every weekend.

So.. I recently switched over to the SWG system and have been playing with unit trying to get my FC just right. With my IC-40 set at 40% and the pump running 10 hours per day (1500 rpm) I've been sitting at 5.5- 6 ppm. I usually also see .5 cc pushing my TC to 6.5.

So now that I've gotten the hang of things, I've been using my Taylor OTO kit to make the daily adjustments and with frequent verification using the DPD kit, I'm usually within .5 ppm on the FC. Recently in the last few days, I've been using the OTO kit and its only registering around 0.5ppm of Chlorine, which I figured was due to some heavy rain we've had. So, I added a little bit of liquid chlorine to kinda give it a jump start a few days ago. Today, I came home and tested again, and got the same results. So I added the Pool calculators recommendation of 72 oz of liquid to raise my .05 to 3ppm (23000 gal pool). I then waited an hour with the pump running on high speed and tested again. I got the same results of 0.5ppm. I felt this was odd, so I did two back to DPD test and got 11ppm for chlorine level. HOLY COW!!

So the question is.. did my OTO test kit go bad? I store it under a covered patio inside of the cardboard box I received it in.
 
First, you have the OTO and the FAS-DPD chlorine tests ... the DPD test is different and it is not in the TF100.

That does not make a whole lot of sense as the OTO can not "bleach-out" due to high levels of FC like the DPD will. With a FC around 11ppm, the OTO should be showing a pretty deep orange.

How old is the kit? Would be better to store inside out of the heat.
 
Kit is only 3 months old max... Hottest it has been is 92 degrees, but that only lasted two days before the rains came. Even with that, kit is stored out of the sunlight, in a box under a large covered patio. Its just funny that kit was very accurate about 5-6 days ago, then all of sudden the kit is way off.
 
Okay... this is just strange... Just retested using the Basic kit using the R-0600 for the Chlorine test / R-0014 (Phenal Red) for PH and the test came out exactly like it should have with 11ppm of FC. Comparator was orange like a pumpkin for the Chlorine and the PH was 7.2 exactly like the calculator said it would be.

hmm... I wouldn't put it past myself to use R-0003 instead of the R-0600... but I keep them separate... :hammer:
 
Killer95Stang said:
Okay... this is just strange... Just retested using the Basic kit using the R-0600 for the Chlorine test / R-0014 (Phenal Red) for PH and the test came out exactly like it should have with 11ppm of FC. Comparator was orange like a pumpkin for the Chlorine and the PH was 7.2 exactly like the calculator said it would be.

hmm... I wouldn't put it past myself to use R-0003 instead of the R-0600... but I keep them separate... :hammer:
Click to expand...
Anytime my results suddenly make no sense, I suspect testing error.

Many is the time I've added reagents to test CH in a 10 ml sample only to realize when it's still not changing colors that I filled the vial to 25... Or added the TA reagents and then tried using the R-0012.

That's the beauty of doing it yourself - you know when something doesn't seem right!
 
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