Pool Test Kits

[chem geek]

In this post I compare the Taylor K-2006 against some test strips. There is really no comparison in resolution nor accuracy. Also, as Ben mentioned, the K-2006 uses a FAS-DPD chlorine test that does not bleach out at high chlorine levels the way the DPD test does and it is more accurate to within 0.2 ppm for a 25 ml sample size and can even read up to 50 ppm (using more DPD powder). The less expensive DPD chlorine test that is read visually only goes from 0-5 ppm with roughly 1 ppm accuracy though even that's a stretch.

[CarlD]

And the only strips that are even vaguely useful are the high-end Hach and LaMotte 6-way strips that have the CYA test. Still I mainly use them as go/no-go gauges...if they are very purple I don't need chlorine. If they are pinking out, I probably need it, and if they are white, open the carboy!

Carl

[SalemCastles]

I'm a fairly technical guy that appreciates precision when it's needed. I'm at a loss as to why I would (should?) be concerned about a .2ppm change in anything. I have easily kept my pool balanced enough to enjoy using test strips of various manufacturers. I presently use Aqua Chems 6 way strips. I do agree with using them as go no-go gauges. My interest in getting a good test kit is more from an economic interest, in that the fun now is to keep it balanced for the least amount of money. However; I still do not see me ever making .2ppm adjustments. What am I missing?

Glenn in Toronto

[PoolDoc]

Chem_geek really, really likes precision. In some of his pool work, those determinations matter when you are attempting (as he is) to understand what's happening with the pool chemistry, at an analytical level. But you are right that 0.2 ppm chlorine rarely matters for most pool operators. However as he also notes (more importantly) DPD-FAS allows measurement of high levels of chlorine.

Generally, you can't manage chlorine at high CYA levels, not because of 0.2 ppm differences, but because of 10 ppm differences. Only the DPD-FAS kits allow reliable distinction between 10 ppm and 25 ppm FC.

Or, if you mess around with copper (ionizers, "minerals", etc.), 400 ppb Cu may not stain; 600 ppb probably will. Target levels are often in the 300 - 500 ppb range (0.3 - 0.5 ppm).

Ben

[SalemCastles]

There is really no comparison in resolution nor accuracy. Also, as Ben mentioned, the K-2006 uses a FAS-DPD chlorine test that does not bleach out at high chlorine levels the way the DPD test does and it is more accurate to within 0.2 ppm for a 25 ml sample size and can even read up to 50 ppm (using more DPD powder). The less expensive DPD chlorine test that is read visually only goes from 0-5 ppm with roughly 1 ppm accuracy though even that's a stretch.

I guess I'm challenging the notion that it's the resolution that makes a good kit necessary as it keeps being compared to the strips when as you have just explained quite simply it's the range that really matters in certain circumstances. I can see you would want a consistent resolution over that range. Thanks for putting it into a context I can more easily understand. I use a safety cover over the winter and change out at least half the water each season so do not have high CYA issues and don't mess around with copper thanks again to you and this forum

Glenn

[PoolDoc]

Yeah, I don't think Chem_geek was really arguing that the 0.2 FC resolution was the key point; it was just a topical fact.

But he and I both have a tendency, when we post, to do an information dump of what we know on a topic, without running the "what information is relevant here?" filter as much as we should. Sometimes, that's because we don't know for sure what the OP needs to know, but sometimes it's just a matter of "if we know it, we say it".

Ben

[CarlD]

Glenn,
I use strips, have excellent color perception (unusual for a male but even my wife acknowledges it) so that's not a problem, but I don't rely on them. They are the canary in the coal mine to me--early warning of a problem. That's because I cannot tell if my pH is 7, 7.2, 7.6 or 7.8 using strips. Also, strips max out on FC at 10ppm. If you need to shock to 12, 15, 20 or 25ppm, they are useless. For CYA, they are inevitably wrong, and the TC tab on the strip usually reads lower than the FC, which isn't possible.

With FAS/DPD you CAN read changes in FC or CC down to .2, but rarely will you ever. Most of us ALWAYS use the .5 scale. The ONLY time I have ever found the .2 scale useful is if I see a CC of .5 or less I can't seem to get rid of. Then I'll measure at the .2 scale and, inevitably, the CC reading is .2 or less, which IS trivial. But if it's higher than .2, but still lower than .5, I'll want to shock the pool before it becomes a problem.

There is a way to use OTO testing to read higher than 3 or 5ppm, which works (search for the CarlD Shot Glass Method, or CarlD Patented Shot Glass Method ) by diluting with distilled water, but accuracy drops with each level of dilution.

Carl

[chem geek]

Yes, I wasn't recommending using a 25 ml sample with 0.2 ppm precision and accuracy, but rather that you COULD be that accurate if you wanted to and that it says something about the quality of the test. Most people use a 10 ml sample for 0.5 ppm precision and accuracy which is fine in most circumstances. For my own pool where I find the 0.2 ppm resolution useful is in two situations: 1) when I want a better handle on the Combined Chlorine (CC) level which is always very low in my pool (i.e. I want to know more than just <= 0.5 ppm; I want to know if it's <= 0.2 ppm) and 2) when doing an overnight chlorine loss test since such losses are also low or even when doing a daytime loss test. These latter loss tests are useful for figuring out average chlorine demand to the point where I can even tell when my wife has peed in the pool (see this thread, for example).

[pratzert]

Ben,

Do you plan to sell your tweaked test kits again or are you advising everyone to use the k2006 ?

How about refills of specific agents ?

Thanks, Tim

[aylad]

For the time being, there are several places online that you can get the reagents, whether it's Taylor's or Ben's kit. You can get them from the Taylor site, but I find spspoolspas.com has some of the most competitive prices. Some people have ordered from them and not been satisfied with their service, but I've never had a problem with them. Others use amato industries. If you need the crosslink between Ben's reagents and Taylor's, let me know, I think I still have it bookmarked.

Janet