Photometer testers

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The most common/popular of the available Photometer testers is the Lamotte ColorQ

But, what we have found in practice is that you can not confuse the specificity of the results the ColorQ gives with accuracy. We have had members attempt to use the ColorQ to follow our methods and almost all have abandoned its use due to inaccuracies and inconsistencies.

We even had one member test the same sample of water three times in a row and ended up with three different sets of results. Here is an example of a ColorQ post: ColorQ vs TF100 and here is a review where the Color Q was used alongside a TF-100. Test Kit Comparison

Realistically, with the ColorQ you are using the Lamotte version of a Taylor K-2005 DPD Test Kit, but the ColorQ "interprets" the colors/readings for you. As calibration is part of the start up sequence (for those that I have read thru the instructions) that is not an issue. What may be an issue is failing to keep the tube(s) clean. Additionally, should you ever have the need to SLAM Process the pool you will be unable to do so with the ColorQ due to the limitation of testing FC up to 10. After 10 it just says "High"

Please do not read this to say that we are "down" on the ColorQ. To quote Dave, Site Owner of TFP:
Throughout TFP, you will read that we suggest certain levels that good science and practical experience has taught us fall within safe ranges.

Further reading of posts here will draw you to the inescapable conclusion that these guidelines work.......in thousands and thousands of pools worldwide.

You may or may not choose to use these methods and guidelines or you may use some and not others. Our goal is to teach you what has been proven time and time again and then let you use that information to your benefit.
Click to expand...

We have found that drop based testing using Taylor reagents provides accurate and repeatable test results. These are what we need to make reasonable recommendations for pool chemical additions which is why we always come back to them.

If you do go with a photometer tester you could be the one to make us feel comfortable about the device. But, to do that you would need to consistently test with both the meter and Taylor drop based testing while keeping a log of the results from both. Several folks have said they use them with no issues, but none have proven it with comparative testing.
 
Hi Tim,
Great topic. I was not specifically referring to Lamotte photometer testers, but lets use the Q series as the discussion point.

1. specificity seems to be on spot. However maybe we should add sensitivity as well. For example lets go with the goal is to detect why the pool is sick or if the pool vulnerable to sickness. To simplify goal Specificity == False Negatives with false positives low and Sensitivity == True Positives with false negatives low
2. To keep false positives and false negatives low, reliability is a key point. A couple of points to reliability is repeatability and reproducibility.
3. What are factors to make a pool test repeatable and reproducible? - repeat measurements recording the variation in measurements taken by a test procedure or person under the same conditions. Reproducible measures whether an entire experiment can be reproduced in its entirety.
Was the above criteria followed in the examples provided? I don’t doubt the results , however don’t know the why the results vary.

I have seen the what is listed above done with photometers and the Lamotte referenced without the inconstancies and inaccuracies. Although inaccuracies is subjective - meaning is Taylor kit really a golden standard. Food for thought, a Taylor kit test repeating with different bottles of Taylor reactants produced significant differences in FC results. Factors found - 1) one bottle expired 2) fresh bottle 3) rebranded Taylor bottle. On rebranded bottle it was observed that the drop volume was not constant with Taylor standards.

Enough for now, later we can discuss effects of the above on healthy and a sick pool.

As for the over range, why exclude dilution which is acceptable by Taylor and Lamotte?

Regards,
CaveDiver
 
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