Leslie's Digital Water Chemistry

[JPMorgan]

I was at Leslie's yesterday and took a sample of water to be tested to compare to my own test results. The store I go to had a new digital water tester. In about a minute they gave me precise results, i.e., CYA=28, CH=208 vs. the "rough" results I get with my tests. I had calculated my CYA to be about 30 and CH about 220. I was wondering if others have had any experience with these digital pool water measurements and if they are reliable. They certainly are more precise, but I'm not sure about reliability. They did not try to sell me anything based on the results. The store rep simply said your chemistry looks really good. Anyone have an opinion on whether these digital readouts can give more accurate measurements than I can get with my test kit? It was encouraging that they were very close to the results that I was getting on all measures. I usually have the most difficulty measuring CYA and CH, so it would be nice to get a "second opinion" from a pool store ocassionally.

 

[Griswald]

Your test results are fine, as shown by the fancy high dollar test at Leslie's.
Rounded off numbers are fine, 30 vs. 28 and 220 vs. 208 makes absolutely no difference in your pool.

 

[Donldson]

Reliable?

No. Those units are almost never calibrated once they hit the store because it doesn't matter if they are calibrated so long as they help push sales. And they do push sales, because a shiny technical looking device convinces people more than some salesperson with a test kit. And don't fall for that imaginary precision, that's literally added to convince people it is accurate. It cannot measure down to the single digit ppm CYA. Digital pool store testing is less reliable than typical pool store testing. Which, as you know, is unreliable.

Trust yourself and don't go seeking "second opinions" from pool stores. If you think you screwed something up, you can always ask here. When have we ever shied away from telling someone they were wrong?

 

[JPMorgan]

Thanks for the thoughts and comments on this.

 

[jfelbab]

Two of my neighbors and myself all arrive at different test results using my Taylor kit. It seems as we all have slightly different eyesight. Recently, I have been backing up my readings with Leslie's new digital testing and I like the fact that their digital testing is repeatable to a degree impossible for me using a manual test. This brings to my mind the question... "How accurate do these tests need to be?" I can take two samples from my pool to Leslies and they yield identical results. My optical results vary slightly ± 5-10% from the Leslie's digital results. I'll keep an eye on this over time to see if their accuracy is reliable.

 

[tim5055]

Please do not confuse the specificity of the results they give with accuracy.

 

[Donldson]

I can take two samples from my pool to Leslies and they yield identical results.

Now see, this is the part where you are either lying, or being lied to. Don't get me wrong, I assume the latter, but regardless it is an impossible statement.

Two different samples will always be slightly different. It might be a few ppm TA, or 0.2 ppm FC, but they will be different. So if you went in to Leslie's with two samples and got identical results, then I don't even think they ran the tests the second time around. Think about it, if it could actually test to the precision it says it does, then you would find minor but measurable differences in the results. If it isn't actually testing to that precision (and it definitely isn't) then the artificial number generator that fills in the final digit would produce different numbers. Either way it would produce different results, whether accurate or not. If this actually happened then my guess is the second test wasn't even run and the same numbers were just spit out because they aren't going to demonstrate to you that their testing is inaccurate.

OR... You didn't actually try this and are just telling us that you could do it because it backs up your story. Not accusing you, but it is one possible conclusion.

 

[tim5055]

Now see, this is the part where you are either lying, or being lied to. Don't get me wrong, I assume the latter, but regardless it is an impossible statement.

Two different samples will always be slightly different. It might be a few ppm TA, or 0.2 ppm FC, but they will be different. So if you went in to Leslie's with two samples and got identical results, then I don't even think they ran the tests the second time around. Think about it, if it could actually test to the precision it says it does, then you would find minor but measurable differences in the results. If it isn't actually testing to that precision (and it definitely isn't) then the artificial number generator that fills in the final digit would produce different numbers. Either way it would produce different results, whether accurate or not. If this actually happened then my guess is the second test wasn't even run and the same numbers were just spit out because they aren't going to demonstrate to you that their testing is inaccurate.

OR... You didn't actually try this and are just telling us that you could do it because it backs up your story. Not accusing you, but it is one possible conclusion.

On days that I was really bored I would visit different pool stores with water samples just to amuse myself. I wasn't going ot buy anything, I just nodded and said "great, I have some of that at home from last time" when they made recommendations.

Three bottles from the same pool taken at the same time revealed numbers way off even considering the time between stores as I ran my errands. I'm talking CYA differences from 60 to 150, TA from 50 to 120 (not adjusted) and CH differences between 100 and 400. Two bottles of water from my pool and what I said was my neighbors pool taken to the same store with the fancy computer also yielded different results that gave different fixes being recommended for each pool.

The store I went to that got it the closest to my readings was a store that used Taylor drop based testing, but only when the owner did the testing. I would watch carefully as people did the test. The owner was deliberate and followed proper testing protocols. One kid in particular was never even close His additions of reagent were more like squirts than drops to be counted.

Now, my friend in Miami has a small family owned store near him. Their testing is spot on every time I've been there. They also use Taylor drop based tests, but teh employees have obviously been well trained. I've tested his water before we went to the store and they were almost always spot on or within a one drop of reagent different.

 

[pookiesunshine]

Now see, this is the part where you are either lying, or being lied to. Don't get me wrong, I assume the latter, but regardless it is an impossible statement.

Two different samples will always be slightly different. It might be a few ppm TA, or 0.2 ppm FC, but they will be different. So if you went in to Leslie's with two samples and got identical results, then I don't even think they ran the tests the second time around. Think about it, if it could actually test to the precision it says it does, then you would find minor but measurable differences in the results. If it isn't actually testing to that precision (and it definitely isn't) then the artificial number generator that fills in the final digit would produce different numbers. Either way it would produce different results, whether accurate or not. If this actually happened then my guess is the second test wasn't even run and the same numbers were just spit out because they aren't going to demonstrate to you that their testing is inaccurate.

OR... You didn't actually try this and are just telling us that you could do it because it backs up your story. Not accusing you, but it is one possible conclusion.

another possibility is that he meant nearly identical and not precisely identical. and yes, if this is true, a better expression would have been "essentially the same". of course i have no knowledge of what he really meant.

 

[duraleigh]

so it would be nice to get a "second opinion" from a pool store ocassionally.

Perhaps, but if that opinion is bogus to begin with (and it is), what is the point?

"Hmmmm. My own tests reveal 2+2=4. However, the shiny new digital tester at the pool store says 2+2=5"

A basic tenant of what we teach is to purchase a test kit you can trust and trust your own testing. Over and over we see people trust the shiny, whirring digital tester and question their own work.

Just keep reading and learning, folks. Many of us at TFP have been doing this close to 15 years......we are not wrong.

 

[JPMorgan]

Just got back from Leslie's which will be my last trip there for water testing. According to their test, my CC was 2.42. On my own test, I get less than .5. Tried to sell me non-chlorine shock due to my "high CC", as well as Phos Free for my high phosphate levels. I agree with the Experts here.... trust your own testing. My pool is crystal clear and my water chemistry is very good based on my testing. According to Leslie's, I need to add their "stuff" to deal with my high CC and high phosphates. I see Leslie's doing a real dis-service to a lot of pool owners. Stick with TFP methods (including doing your own testing, using basic ingredients for balancing, and liquid chlorine and you will have a "happy" pool.

 

[tim5055]

I see Leslie's doing a real dis-service to a lot of pool owners.

They are commissioned sales people and the management makes a bonus off what their employees sell.

 

[JPMorgan]

Correction: In my previous post I said that Leslie's test showed CC of 2.42. That was actually the TC reading, but my FC was 2.08, so less than .5 on CC. They flagged the "high TC" on their test results and suggested I use a non-chlorine shock to address the "high TC". It's my understanding (based on information on this site) that CC below .5 is not an issue, nor do I need to "shock weekly" as was recommended by Leslie's. I have had great pool water for a couple of years now following TFP advice and almost never shock my pool anymore (except at open). I won't be making any more trips to Leslie's. All the information needed for terrific pool water is right here on TFP!

 

[jfelbab]

Update regarding the identical tests numbers I received at my nearby Leslie's. I discovered through a long discussion with the store's management that their shiny new digital testing device has been on the blink for the past month and they have been using some test strips and just making up readings for the items not easily tested like Copper, Iron, Phosphates, etc. I don't doubt their expensive automated test device can yield accurate results when routinely calibrated and is operating properly but clearly this store is not to be trusted. I would have felt better if they had informed me that the machine was broken and they were simply using test strips but they chose not to do so. I don't appreciate being misled and won't be back.

TY all.

 

[Donldson]

Thank you very much for sharing that.

If that doesn't cement why we refuse to trust pool store testing, I don't know what will. It would be a considerable stretch of logic to think that you stumbled in to the only untrustworthy Leslie's in the country. It rather proves my point that accurate testing is not the purpose of those machines, but getting people in the store. Otherwise they wouldn't have lied about it, right? Or they would have gotten it fixed by now, right? They admitted to literally making up phosphate numbers when we know that one of their most profitable items is PhosFree! Imagine that, making up test results that push sales. Who would have guessed that?

Those units are almost never calibrated once they hit the store because it doesn't matter if they are calibrated so long as they help push sales. And they do push sales, because a shiny technical looking device convinces people more than some salesperson with a test kit.

The pieces all start to fall in to place.

 

[poolpsycho]

I trust the digital test far more than the human doing the test. I have watched the humans not following the time, drops, mixing the samples, the accuracy of the amount of water sample used, etc., much to my dissatisfaction! Someone's eyes may not be as accurate as another person. Also, their interpretation of what they see may be off as well. At least, the computer is consistent. The results may be off, but they are consistent.

 

[duraleigh]

I trust the digital test far more than the human doing the test.

How about if you were the human doing your OWN testing.......would you still trust the digital test more?

 

[poolpsycho]

Yes, I would trust the digital test over my eyes. The main reason is when I look through the sample compared with the backlight being the sky, the sky, and the light changes constantly. Using the digital method, the light is pretty constant being it is in the machine.

 

[Donldson]

If you really think, "I don't care if it's wrong, as long as it's consistently wrong" makes sense, then I guess there isn't much we can say. Clearly we have very different goals in pool testing than you.

 

[Oly]

The main reason is when I look through the sample compared with the backlight being the sky, the sky, and the light changes constantly.

Regarding the pH test you can control the backlight with white paper. Also any changes to the backlighting will change both the comparitor standard and the water sample equally.