Testing for high chlorine levels

Its always good to find another authoritative web site for pool maintenance! I've been through the pool store jungle of mystery potions which don't seem to do much except drain my wallet. Now I use my local dealer for cyanuric acid, a gel block for the skimmer to clear the water (it does work, but sloooowly) and tests to compare with my own results.

I've been using the bleach shock method with good results. I do find that the OTO chlorine test using a crude titration method doesn't let me directly read the high levels for effective shocking. To compensate I've diluted the pool sample with an equal amount of distilled water, and then doubled the indicated level after adding the prescribed 5 drops. Is this a reasonably accurate method? The strips are hopeless for this....

Wow. Answering this is a hoot!

If we've answered that question once this season, we've answered 500 times. But this is the first time, I recall someone asking. Normally, we answer because WE know they need to know, not because THEY have realized they need to know.

Anyhow, the answer is, "You need a Taylor K2006. Full info is in the test kit page linked in my signature. Meanwhile, if you maybe able to get a HTH 6-way kit at a Walmart near you check availability). It's a private labeled Taylor kit that is compatible with the K2006."

The kit I have, from Leslie's, looks equivalent to the listing for the K2006 as illustrated in Amazon, with the exception of cyanuric acid. I have a separate test kit for that. The Leslie's kit allows me to measure pH and acid demand, total hardness/alkalinity, and, of course chlorine levels. My kit uses two tiny tubes with colored patches corresponding to chlorine levels and pH.

This is not very precise; a better way would be to use a proper indicator and count the number of drops and then convert to chlorine or pH. As I remember my qualitative and quantitative analysis college chemistry courses many years ago this would be "easy" for pH; I have no ready idea what indicator would work for chlorine.

I'm not sure that I stated my question accurately. If I dilute the pool water with an equal amount of distilled water (to avoid any domestic supply chlorine) and then test for chlorine levels, wouldn't the indicated levels with the test kit represent 1/2 of the chlorine levels of the undiluted sample? So an indicated 5ppm via the kit would actually be 10ppm?

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Originally Posted by George in GA

My kit uses two tiny tubes with colored patches corresponding to chlorine levels and pH.

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You probably have the K-2005, which Leslies's sells. The problem is (a) the red shade is one a lot of people have trouble with, (b) the range only goes to 5 ppm -- some kits 'read' higher, but people don't, & (c) DPD color match reads 0 ppm for levels that are 0.0 ppm FC *and* for levels that are 15 ppm FC!

You need the K-1515.

Phenol red color match is sufficient for the task, unless you are color blind. Acid and base demand can be used to quantify pH levels outside the measurable range.

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This is not very precise; a better way would be to use a proper indicator and count the number of drops and then convert to chlorine or pH.

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It would be more precise, but would not necessarily be better. More precise is ONLY better when you NEED more precision; otherwise, more precision is just a PITA.

I constantly have to fight some people's tendency to try to run a set of numbers, instead of a pool!

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As I remember my qualitative and quantitative analysis college chemistry courses many years ago this would be "easy" for pH; I have no ready idea what indicator would work for chlorine.

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As it happens, the acid / base demand test in the K2005/6 -- if that is what you have -- operates as close to that as you will get with pH. If you want ACCURATE pH results, you need a double buffer calibrated pH meter. But, the only people that normally NEED such a meter are those with color perception probelms.

Also, in the K-2005/6, both the alkalinity and calcium hardness tests are straightforward titrations with an indicator (methyl orange; Calcon): the only difference is you are using a dropper tip instead of a titration and a tube instead of a flask.

In the K-2006 -- and this is the critical difference -- the chlorine test is ALSO a back-titration, with "FAS" -- ferric ammonium sulfate -- to a 0.0 ppm FC level

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If I dilute the pool water with an equal amount of distilled water (to avoid any domestic supply chlorine) and then test for chlorine levels, wouldn't the indicated levels with the test kit represent 1/2 of the chlorine levels of the undiluted sample? So an indicated 5ppm via the kit would actually be 10ppm?

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That process is described in the "How to test without a good testkit" sticky.

Sorry to have bothered.

I'm sorry for being 'testy'; it's been a very long week, and I'm about used up. Newbies are newbies, educated or not, and I know that. God knows I've done enough of that myself!

But it takes a bit of self-control -- never one of my strengths -- to avoid snapping at people who ask unnecessary questions, like yours. As in every area of life, solving problems is maybe 20% technical and 80% people, and I know that too.

There's not much for me to take back; everything I told you is both true and relevant, and if there's a way to 'take back' having said it badly, I've never discovered it! Again, as God knows, it's something I could have used many, many times.

So, yes, you 'bothered' me, and yes, your questions were unnecessary to the function of your pool. But it's part of the learning process, and I responded badly. I hope you'll forgive me.

Just to simplify: If you have the Leslies equivalent of the K-2005 (and, yes, Leslies sells it--it's actually a Taylor re-badged) then all you need is the Taylor K-1515 to "convert" the K2005 to the recommended K-2006. You use the FAS-DPD chlorine test instead of the DPD Chlorine test.

You CAN use the "Patented (j/k) CarlD Shot Glass Method" with an OTO tester like you have to double, triple or even quadruple the reading, using distilled water as you did. However, if you search the forum, you'll find Ben posted another way to use the OTO kit to measure without dilution, with reflecting what it means when the test goes deeper yellow, orange, deep orange, then brown ( I think brown is around 40? ppm?) But you don't get the FC and CC reading, only TC.

BTW, Leslies also sells a re-branded version of the Taylor K-2006 kit.

Carl

Apology accepted.

As one who has taught and as a retired librarian I can well understand the fatigue of fielding the same question over and over and.... I often had to tell myself that the d*** fool question wasn't unnecessary to the seeker.

The main reason I asked the question, BTW, was to fulfill the posting requirement of the site. Perhaps I just should have said "Hello."

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Originally Posted by George in GA

The kit I have, from Leslie's, looks equivalent to the listing for the K2006 as illustrated in Amazon, with the exception of cyanuric acid. I have a separate test kit for that. The Leslie's kit allows me to measure pH and acid demand, total hardness/alkalinity, and, of course chlorine levels. My kit uses two tiny tubes with colored patches corresponding to chlorine levels and pH.

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IFthe kit you have uses DPD for testing FC and TC (3 chlorine testing reagents and comparator block in shades of red) it is a Taylor K-1004 and the only test that is the same as the one in the K-2006 is the TA test. Leslies calls iti the DPD Deluxe test kit. IF your kit uses OTO for TC testing (1 chlorine testing reagent and comparator block in shades of yellow) it is the Leslie OTO deluxe test kit and does not have an equivalent Taylor kit (closest is the K-1003 which also includes a base demand test). In either case your kit does not include tests for CYA nor for calcium hardness. Both of these kits test pH with the R-0014 reagent that uses the small and less precise comparator instead of the R-0004 pH reagent and the large comparator and only included the acid demand test. Total hardness and Total alkalinity are separate tests and total hardness is a useless test for pools since we are interested in calcium hardness. Test strip and the HTH test kit test total hardness so this test is really not giving us any useful info. Even with a vinyl pool one shouhd test their calcium hardness. Just because a vinyl pool does not need ADDITONAL calcium the calcium hardness should be kinown in case any water balance adjustments to pH or TA are in order to lower the possiblity of scale formation (which can ruin a liner pool the same as any other surface).
You would be best served by getting a K-2006 test kit. Your current kit is not even close. Sorry.

As far as dilutions for testing higher FC levels, it can be done with either OTO or DPD and the instructions for doing so are included with the 2000 series kits along with markings on the 2000 series comparators for how much distilled water and pool water to use for 1:1 and 1:4 dilutions. However, it is a cumbersome and error prone process. Once again, the FAS-DPD test is far superior in any case.
Dilutions are easy to do. Just mix a measured amount of pool water with a measured amount of distilled water and test. Multiply your results by the dilution amount:
1 part pool water and 1 part distilled water multiply test results by 2
1 part pool water and 2 parts distilled water multiply test results by 3
1 part pool water and 3 parts distilled water multiply test results by 4
1 part pool water and 4 parts distilled water multiply test results by 5

I would not recommend going higher than a 4:1 dilution since the possibility of too much error and realize that the more you dilute the less precison the test result has. Once again the FS-DPD test is far superior since it can give a precision up to .2 ppm with FC as high as about 50 ppm.