CL eliminator required in TF-100 in pool tests???

mmcwhorter · Jul 23, 2015

I am the proud owner of a new TF-100 test kit. I have a high degree of confidence in this test most excellent kit.

In the past, with other less competent test kits you would be instructed to first use one drop of #4 CL eliminator in the test vial for ALK and PH tests, as they said high levels of CL cause errors. Understandable.

So, my question is: is this #4 CL eliminator required using TF-100 kit?

It does not call for it...and there is no #4 reagent in the kit.

After SLAM (which worked GREAT) and with CYA at >80...I have to keep FC readings above 10 due to high CYA and until I get that fixed I want to be sure my ALK and PH reading are accurate.

I am betting that the good folks who came up with it made it "bulletproof" for us home owners...but I had to ask.

Thanks so much!

YippeeSkippy · Jul 23, 2015

Nope, no need to add anything other than what's in the kit and per instructions although when chlorine is over 10ppm the pH is not accurate.

JoyfulNoise · Jul 23, 2015

The Taylor R-0007 drops are the sodium thiosulfate dechlorinator. They are only used for the TA test as all other indicators have de chlorination built into them or are not sensitive to chlorine bleaching/interference.

That being said, you can not do pH test with your FC higher than 10ppm. The R-0007 drops react with chlorine in a non-neutral way meaning the pH can go up or down. So you can not add R-0007 to the water sample before doing a pH test.

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JoyfulNoise · Jul 23, 2015

If you want to do a less than accurate pH test with your FC between 10-20ppm, you can dilute your test water sample 1:1 with DISTILLED water (the kind you buy in the supermarket for use in irons and coffee pots). Bottled water or tap water will not work. The dilution with distilled water will cut the FC concentration in half without affecting the pH in any measurable way ASSUMING the TA of your pool water is within normal ranges.

It's not as accurate as the standard pH measurement but it does work.

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wisco · Jul 23, 2015

So what is it about a FC > 10ppm that screws up the pH test? Is that just a thing with Taylor's particular test or would that be the same for any phenol red test?

JoyfulNoise · Jul 23, 2015

wisco said:
So what is it about a FC > 10ppm that screws up the pH test? Is that just a thing with Taylor's particular test or would that be the same for any phenol red test?

Phenol red, in the presence of hypochlorous acid gets concerted into chlorohenol red which is also a pH indicator but for a more acidic pKa. At FC higher than 10ppm, a significant fraction of chlorphenol red is present with the phenol red and it interferes with the color comparison. The chlorphenol red becomes purple colored at typical pool pH and thus makes the pH test read high.

The phenol red indicator in the Taylor kit is actually one of the best formulations out there because it has additives in it that allows it to operate at much higher FC levels than any other manufacturer. It can still function at FC levels between 10-15ppm but the results are not as accurate. Past 15ppm it really stops working. But that is much much better than any other manufacturers.

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mmcwhorter · Jul 24, 2015

So, I will conclude from all herein that the Taylor R-0007 is the same thing as the #4 in my "Home Depot" Pool Time brand 5 way kit.....right? And if FC > 10, pH test in TF-100 is not accurate. I'll look in to getting some di water....but once I get me CYA back in control (80 now) and down to 40 ppm, I don't think I'll have to worry about it.

JoyfulNoise · Jul 24, 2015

mmcwhorter10 said:
So, I will conclude from all herein that the Taylor R-0007 is the same thing as the #4 in my "Home Depot" Pool Time brand 5 way kit.....right? And if FC > 10, pH test in TF-100 is not accurate. I'll look in to getting some di water....but once I get me CYA back in control (80 now) and down to 40 ppm, I don't think I'll have to worry about it.

I would not assume the R-0007 is the same as the PoolMaster #4 solution. The Taylor phenol red is a different formulation (based on other additives) than the PoolMaster phenol red. Taylor often puts additives into its various drops to correct for interferences that might occur. I would not assume other manufacturers do the same or that different drops are interchangeable.

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chem geek · Jul 26, 2015

By the way, the chlorination of the phenol red is not very fast so in pools with CYA one can often get an accurate pH reading before that purple color develops. Of course, that's tricky to define so we don't both with that in any instructions. Instead, it's more reliable just to dilute the sample with distilled water (not tap or filtered or buffered water) and retest. Or wait until the FC drops to 10 ppm FC or lower.