Testing sample size variation with Clear Choice Labs kits - should be 10ml

AusPhil

Well-known member
Jan 23, 2018
99
Canberra ACT
CYA doesn’t interfere to cause a high reading on the TA test, it is part of the total alkalinity and should be accounted for. CYA, borate and carbonate are the major species that interact to stabilise the pH and are all part of the total alkalinity. If present, all three are accounted for as part of the total alkalinity test. Removing the CYA portion is an ‘old school’ pool industry thing, TFP does not remove the CYA portion, that would lead you to over dose with baking Soda and artificially raise your TA too high. Removing the CYA borate portion leaves you with carbonate alkalinity and is done automatically to calculate CSI.
So Taylor Technologies, the gold standard held up by TFP has it wrong in their own notes about their own reagents for drop tests....... Technical FAQs ...

Note i'm very happy to learn if they have just i would think that they would themselves know how they own reagents react.
 

AUSpool

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TFP Guide
Sep 23, 2015
717
Brisbane, Australia.
I wouldn’t blame or question Taylor, they supply quality tests, but its the LPSs that profit from the results. By lowering the alkalinity value the LPSs are presented with an opportunity to sell you something you didn’t think you needed. With TA in my tap water I don’t need to add any, just the opposite, I need to work at reducing it.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
16,031
Tucson, AZ
You only need to worry about adjusted alkalinity if you are doing saturation (CSI) calculations by hand or using a chart to dose a pool with bicarbonate . The PoolMath App (and the old Pool Math webpage) already account for cyanurate and borate alkalinity in all of its calculations.

As for using pipettes, scales, graduated cylinders, and digital pH meters, all that can be said is that it’s your pool and your time. If one wants to spend a lot of time trying to achieve lab-scale accuracy in their pool water measurements, go for it. It’s certainly not going to change the way a pool is cared for and it’s not going to result in some amazingly different wate feel. People can swim in water with a pH anywhere from 6.8 to 8.4 and never know the difference nor can they feel a difference in water with high or low alkalinity. So having accuracy any better than 0.1 is mostly unnecessary.
 
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AUSpool

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Sep 23, 2015
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Thanks Matt, that’s what I was looking for.

So Taylor Technologies, the gold standard held up by TFP has it wrong in their own notes about their own reagents for drop tests....... Technical FAQs ...

Note i'm very happy to learn if they have just i would think that they would themselves know how they own reagents react.
There is an interference from high FC but if you read through the Taylor TA section in the FAQs carefully and go on to refer to the ‘Testing and Treatment Guide’ they say that the cyanurate ion produces a high reading. Its not referred to as an interference, it doesn’t interfere with the reagents and Taylor acknowledges that the cyanurate ion is part of the total alkalinity. Taylor and TFP are mostly on the same page. Taylor need to adjust the TA to essentially produce a carbonate alkalinity value that is then used on the next page of the ‘Testing and Treatment Guide’ to produce their saturation index (SI).

TFP just keep it simple and use the total alkalinity value as produced by the test. As Joyful said, PoolMath does the calculations for us when the TA is used to produce the CSI. If an ‘adjusted value’ was entered into PoolMath it would be introducing noticeable error factor. In reality the 33% correction in itself is a simplification, its only 33% at a pH of 7.6. In reality the cyanurate ion concentration is pH dependant where its 0.22%@pH7 and 0.36%@pH8. I believe that the TFP PoolMath accounts for this variation and also adjusts for the borate alkalinity.
 
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imagineero

Member
Nov 24, 2019
16
sydney australia
So having accuracy any better than 0.1 is mostly unnecessary.
Speaking for myself only, the certainty of the accuracy is more of a concern than the resolution of it. I like to get things done efficiently in my life without trouble, which is why TFP got my attention. For someone with your knowledge and experience, I don’t doubt you could turn the swamps of hades into pristine waters with the most basic of test equipment from any local hardware store. Because you have a good understanding of the relative importance of the variables, their interactions, and what to expect. People with knowledge and experience can often get anything pretty close to right, even without the benefit of the best tools.

For myself, I’m a blind man’s stumbling along in the dark without a cane. From my limited time dealing with pools (about 3 months totally) it seems like a huge number of unfortunate souls are in an even worse position! I really have very little idea about what matters or how much time/care is necessary to get reliable test results, and not much idea how to reduce uncertainty (or if I even need to) beyond what I’ve got. Seems to be working so far, be nice to know it was working!
 

BrettClearChoiceLabs

Gold Supporter
In The Industry
Oct 24, 2016
61
Brisbane, Australia
Accuracy eh? How accurate or precise do we need to be with pool testing? This fills my waking days this question does so I'll chime in a little here. I live in two camps with this one, because obviously when I'm making something like a reagent it's got to be super accurate for so many reasons. When I'm actually using the kit though, I'm a lot more relaxed. I hope I'm not opening too big a can of worms with this one :ROFLMAO: 🥫🥫🥫🥫

Massive amounts of caveats go here 😅😅 the biggest one being this is all very much just my opinion

I feel like accuracy vs precision is an important distinction to make here. Accuracy being how close our result is to reality, and precision being the variation you get when repeating a test. Both would be ideal, but if I had to sacrifice one it'd be precision. This is why I think test kits are built with ease in mind, so you do the tests more frequently and get the benefit of averaging and accuracy via statistics. A bunch of loosely grouped shots at goal are more likely to hit than a bunch of tightly clustered shots not on goal.

We assume then, based on how chemistry works, that a drop test done enough times is going to approach accuracy. Between averaging data points and the fact a set number of blah blah bits of chemistry talk bond to a set number of super tiny blehs blehs in each microlitre and cause a colour change, we get results that approach the actual reality of the chemicals. Precision (variation) is harder and more costly to achieve as you get down to the pointy end, and things outside kit makers control (like temperature etc) become more important. Accuracy is cheaper and IMO more effective.

If you're testing with high precision (consistently getting a similar result) but that result is wrong, you'll always be out. You'll see data movement, and you'll know when your TA rises and your CYA drops and vaguely by how much, but you'll never know that it's actually x-20% for example.

Conversely if you test a lot, even if each one is done quickly or you're more of a "near enoughs good enough" person, then the extra data points you've got will smooth the data out. Assuming you're still following the instructions and staying vaguely within the lines :ROFLMAO: Any imprecision caused by these quicker test methods will be reduced by the accuracy/averaging of more data points. A good test kit should be designed to encourage repetition and therefore accuracy rather than precision, and also reduce any variance/imprecision as much as possible. Again, that's my opinion but if Taylor wants to call me and argue for some reason, then I'm sure they can :crazy:

The dream of course, is a high precision, high accuracy test. Chemical drop tests take care of a lot of the precision, because x number of ions swirling around in the jigamarator will always bond with y number of thingos on the z axis and make the pretty colours happen (sorry if I lost anyone with that technical jargon). So why I love this thread so much is that it's trying to find the best way of ensuring the right amount of chemicals meet in the magic colour changing tubes. Kit designers then have to balance that with repeatibility and cost, and in a way that encourages repetition and accuracy, which is a whole other set of challenges.
 
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AUSpool

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Sep 23, 2015
717
Brisbane, Australia.
A good explanation Brett. High precision in manufacture/supply will make a kit with best possible accuracy. And on top of that we/you need viability so us Aussie self testers have a viable (cost effective) pool test alternative other than a LPS. Of cause, and regardless of test or manufacturer, it’s best to apply the test as designed. Fill to the line and follow direction, where 10 or 25ml equals 10 or 25mls. 8 or 12mls is close but not close enough, the user could do better.

This is a previously posted image giving visual display of accuracy vs precision.5ECDB196-4C7C-4992-8541-DBAE83278E75.png

Adding to that I do believe that most users with a little practice do get a result with both good precision and accuracy. Where the precision factor is mostl from the manufacturer and the accuracy from the user and following the instructions properly. I often bang on about variance but in reality most (70% or better) of all results will fall very close to the actual. Statistically it will look like this where 70% of all results are right on the money.
D5FFB98C-2934-46E6-A4E6-51975F937B7A.png
 
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BrettClearChoiceLabs

Gold Supporter
In The Industry
Oct 24, 2016
61
Brisbane, Australia
I love those targets, they just simplify the whole thing so well. I did stats for three years in Uni a very long time ago so I'm a little less fond of seeing that curve again though :crazy: the painful memories of trying to learn maths at 8am!

I agree with your thoughts that accuracy is user based and precision is manufacturer based. Circling back to the start of this thread, I think the main part of our kit that needs looking at next is definitely the viewing tubes. Hand labelling is not precise enough and also not sustainable as the business grows. I'm always trying to improve things in the back end so having you guys dissect the variance in water samples has been massively distracting, fascinating, and ultimately very useful.

I'd love to have a graduated tube premade for us with the correct markings - finding a decent consistent supplier is going to be the issue there. And then making sure their tubes are within the right tolerances and don't cost a fortune. I really do need to make friends with someone who owns a plastics manufacturing company 😅
 
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