Pool test smackdown: Taylor K2006, OTO, Pinch-a-Penny, Pool Store

So I'm into my 8th week of pool ownership. Up until yesterday, I was using my Pinch-a-Penny Basic Test Kit (OTO) to test for chlorine and ph. Over these weeks, the chlorine readings are either a solid 2.0, or maybe a little lighter shade, but not the shade of 1.0 (so I marked down 1.5).

I've also been pitting two "professional" pool companies against each other: a local Pinch-a-Penny store, and another store called, simply, The Pool Store. Pinch-a-Penny appears to rely on some dropper-based testing. The Pool Store relies on a computer and a test strip.

Then yesterday, I received my Taylor K-2006 kit.

Not suprisingly, everybody's tests read somewhat differently.

Among the pros, the points of agreement are with Calcium Hardness and Salt. I couldn't test for these without the K-2006, so that's fine.

The pros differed somewhat on pH testing, but not significantly, and their tests were fairly close to my OTO kit anyway, so that was fine.

The pros differ from each other on Stablizer. (BTW, I take pool samples from the same pool location at the same time, and then turn the two respective bottles over to the pros for evaluation, just to see what they both tell me). But since it's a matter of one pro saying I've got 45 and one says I've got 65 (as was the case today), but both are fairly good numbers, I've not worried about it.

The pros differ wildly on Alkalinity. The dropper-based Pinch-a-Penny test aligns well with my own OTO kit and, now, my Taylor K-2006. Those three tests showed Total Alkalinity of 80 or 90. The test-strip-based Pool Store said my TA was 120. They've consistently give TA results much higher than the others.

But it's testing for chlorine that most puzzles me!

This morning, my OTO kit showed I probably had free chlorine of 1.5. (BTW, the OTO kit says free chlorine can be measured by watching for results a few seconds after dropping in the reagent. Waiting 5 mins or so gives a Total Chlorine reading). Pool Store said I had almost no free chlorine: 0.2, with no Combined Chlorine. Pinch-a-Penny said I had 1.0 Free Chlorine, no Combined Chlorine. So, Pinch-a-Penny and my own OTO kit are pretty much in agreement.

My Taylor K-2006, however, reads quite differently. The Taylor kit read 3.5 for free chlorine, and some trace level of Combined Chlorine (I say "trace" because during that part of the test, the water color was a very slight shade of pink, but turned noticeably clearer when I added that one drop of reagent that calculates CC).

During the free chlorine test using the K-2006, I'm adding drops until the water is *perfectly* clear, where no changes in water color are observed. What that means is that the last 2 or 3 drops of the reagent are changing slightly the shade of pink I observe to an even more slight shade of pink, until the point where the white dot at the bottom of the tube is perfectly white, and I can't observe any further color changes.

So here's the question: When I add the reagent drops to the K-2006 that change the water color from pink to colorless, is the objective to really get it to be 100% colorless, or just mostly colorless with perhaps a slight tinge of pink still remaining? How colorless do you strive to make the water during this test?

If I just went for a big noticeable change away from the pink color, I probably got that within the 4th drop of the reagent. But I had to go to 7 drops (7 * 0.5pppm = 3.5ppm) before it was 100% colorless.

Thoughts?

(I'm about to free myself from testing at The Pool Store, as their tests seem to be mostly the outliers and probably inaccurate to a large degree. I'd like to use Pinch-a-Penny for a "professional" tester that can provide backup against any warranty claims I might need to make in the future against my Diamond Brite pool finish).

Quote:

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Originally Posted by famousdavis

So here's the question: When I add the reagent drops to the K-2006 that change the water color from pink to colorless, is the objective to really get it to be 100% colorless, or just mostly colorless with perhaps a slight tinge of pink still remaining? How colorless do you strive to make the water during this test?

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There are no gradations of 'colorless'. It's an absolute. Colorless = absence of color = clear. A slight tinge of pink means there's still color and you're not done with the titration. Keep adding and counting drops until it is colorless.

AnnaK,

Thanks for the "clarity" of your answer. :-) I wasn't sure just how sensitive the drop testing process is. I guess it's pretty sensitive. Usually when I get to what I think is the last drop, because it looks pretty clear already, I'll add one more drop of the reagent, and then it gets noticeably more white. To paraphrase Horton, A trace is a trace, no matter how small.

All the way to infinity, yeah. But we don't need that sort of precision. When it doesn't get any more colorless you subtract all the drops you added to see if it would and then use that number in your calculation.

Clear? :)

Very clear!

One question, though: If I add another drop to see if it gets clear (during the FC test) -- and it doesn't get any more clear, because it's clear and colorless already -- does that extra drop of reagent goof-up the subsequent test for CC? I'm thinking it wouldn't matter, but I really don't know that for sure.

Quote:

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Originally Posted by famousdavis

Not suprisingly, everybody's tests read somewhat differently.
Pretty much normal...trust your own readings with the K-2006.

The pros differ from each other on Stablizer.
Once again normal, test it yourself.

The pros differ wildly on Alkalinity. The dropper-based Pinch-a-Penny test aligns well with my own OTO kit and, now, my Taylor K-2006. Those three tests showed Total Alkalinity of 80 or 90. The test-strip-based Pool Store said my TA was 120. They've consistently give TA results much higher than the others.
That is one of the big reasons we don't much like test strips with or without a strip reader!
BTW, the OTO kit says free chlorine can be measured by watching for results a few seconds after dropping in the reagent. Waiting 5 mins or so gives a Total Chlorine reading
Wrong Wrong Wrong. OTO tests Total Chlorine. Period!

Pool Store said I had almost no free chlorine: 0.2, with no Combined Chlorine. Pinch-a-Penny said I had 1.0 Free Chlorine, no Combined Chlorine. So, Pinch-a-Penny and my own OTO kit are pretty much in agreement.
Pinch a penny uses Taylor reagents and does DPD testing which is pretty much like OTO except that it will test for FC and TC, unlike OTO.
My Taylor K-2006, however, reads quite differently. The Taylor kit read 3.5 for free chlorine, and some trace level of Combined Chlorine (I say "trace" because during that part of the test, the water color was a very slight shade of pink, but turned noticeably clearer when I added that one drop of reagent that calculates CC).
Count the drops it takes for it to turn colorless. The intensity of the red does not matter. The number of drops it takes to turn it colorless does.

During the free chlorine test using the K-2006, I'm adding drops until the water is *perfectly* clear, where no changes in water color are observed. What that means is that the last 2 or 3 drops of the reagent are changing slightly the shade of pink I observe to an even more slight shade of pink, until the point where the white dot at the bottom of the tube is perfectly white, and I can't observe any further color changes.

So here's the question: When I add the reagent drops to the K-2006 that change the water color from pink to colorless, is the objective to really get it to be 100% colorless, or just mostly colorless with perhaps a slight tinge of pink still remaining?
100% colorless. The test is to keep adding drops until one more drop produces no more color change and then don't count the last drop. It's really pretty easy.
How colorless do you strive to make the water during this test?
Once again, colorless.
If I just went for a big noticeable change away from the pink color, I probably got that within the 4th drop of the reagent. But I had to go to 7 drops (7 * 0.5pppm = 3.5ppm) before it was 100% colorless.

Thoughts?
If it takes 7 drops and an 8th drop produces no more color change then 7 drops it is!
I'd like to use Pinch-a-Penny for a "professional" tester that can provide backup against any warranty claims I might need to make in the future against my Diamond Brite pool finish).

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That is fine but I would not follow their dosing recommendations for pool chemicals. Remember that they are in the business of selling chems.