Calcium Test w/ TF100

[Cayman]

I am testing my CH with the test kit that came wth my TF100. I consistently get readings of 425 yet 2 different pool supply places get a result of 290. This is a drastic difference which makes we question the TF100 reagents, as I follow the directions exactly. My pool builder was even here yesterday and used my test kit and got 425 as well.

Any thoughts or suggestions, as I want to be able to accurately monitor all of this, especially since the finish is only 14 days old.

Thank you.

 

[ajw22]

Trust your TF-100 test. All of our recommendations are based on Taylor Technology testing.

The pool stores are likely testing using different equipment and methods giving different results. If the stores are using Lamotte Color-Q equipment we know that gives different CH reults then Taylor reagent testing.

 

[Cayman]

Trust your TF-100 test. All of our recommendations are based on Taylor Technology testing.

The pool stores are likely testing using different equipment and methods giving different results. If the stores are using Lamotte Color-Q equipment we know that gives different CH reults then Taylor reagent testing.

It appears they use Taylor products, but from what I noticed, they measure when the water turns purple instead of continuing to blue. That is my guess anyways.

 

[ajw22]

Most pool stores employees using reagent testing are poorly trained and sloppy in their procedures which introduce all sorts of errors.

The fact is they don't care if they give you an accurate or inaccurate test result. They just want you to buy something.

 

[Cayman]

Is there somewhere that I can take my pool water to get it truly checked for CH so I can verify 100% that my testing is proper? Or maybe should I buy some strips to try?

 

[ajw22]

Trust your TF-100 testing. It is better then anyplace you will find.

"A man with a watch knows what time it is. A man with two watches is never sure. " - Segal's law - Wikipedia

If you are that concerned buy Standard Solutions to check your testing methods.

 

[Cayman]

Didn’t know that was an option! Perfect! Thank you.

 

[Bvacchiano]

Get the CH Standard solution and test it. It’s a known value and if u get what it says it is then done deal.

 

[Cayman]

Get the CH Standard solution and test it. It’s a known value and if u get what it says it is then done deal.

So my standard solution arrived today and I tested using the 10ml method and the 25ml. The 10ml turns blue after 10 drops which is 250 but the 25ml turns blue after 22 drops, which is 220. The stand solution is supposed to be 200.

So I am even more confused on what to believe, because based on this, each drop would be 20 using the 10ml test.

Thoughts? Any help is appreciated as I am stressed about this.

Thank you.

 

[Rocket J Squirrel]

the 25ml turns blue after 22 drops, which is 220. The stand solution is supposed to be 200.

A 10% error isn't too bad. I never had any luck with the standard solutions. They simply did not read correctly for me and I don't trust them. I trust the Taylor reagents more.

 

[duraleigh]

I never had any luck with the standard solutions. They simply did not read correctly for me and I don't trust them. I trust the Taylor reagents more.

The standard solutions are from Taylor also so I guess you are saying they don't do as well as supplying your own test result and ignoring what Taylor says should be the outcome.

I am not disagreeing with you but am curious that you trust Taylor reagents but don't trust their standard solutions. Which ones did you try?

Now, I hijacked a bit so back to OP's questions.

Any help is appreciated as I am stressed about this.

As Rocket says, there is no need to stress. Plus or minus 10% is pretty acceptable and has no bearing at all on your pool management practices.........especially on the CH test.

 

[JoyfulNoise]

I would redo the test and be very careful when you are titrating. The conversion from red/pink to purple is fast and then the conversion from purple to the pale blue color can be very subtle and slow. You should be doing the test with a speed stir and I would suggest you slow down your drop rate as you get close to the blue endpoint. It’s easy to overshoot and add an extra drop or two. Bright outdoor lighting with a white background helps a lot at detecting the endpoint; indoor lighting is terrible. I would also only use the 25mL test protocol as that will be more accurate and give you finer control over the titration.

 

[IMissNimoy]

I had similar issues with my calcium test and Alkalinity test from a recent TF Test Kit order. I had the Taylor standards and got similar results as the OP. I contacted the TFTestKit.com folks. Very helpful! They advised to wipe the tip of each reagent bottle with a damp rag to insure no debris or static was causing issue. I did that. I got closer on my calcium to be satisfied but both test are still different than my previous (Spring '19) reagents and my neighbor's Taylor kit (not expired). Alkalinity is still way off but I haven't had time to followup with them.

 

[Rocket J Squirrel]

The standard solutions are from Taylor also so I guess you are saying they don't do as well as supplying your own test result and ignoring what Taylor says should be the outcome.

I am not disagreeing with you but am curious that you trust Taylor reagents but don't trust their standard solutions. Which ones did you try?

I think I can almost parse your first sentence.

This was over a year ago, so here's my recollection. The standard solution sampler bottles were not labeled Taylor. They were labeled from TF Test Kits. I assumed TFTK made their own solutions and their accuracy varied or maybe they had expired. Also, at that time I didn't have the Speedstir yet so perhaps my own accuracy varied based on hand swirling.

I trust the Taylor reagents because zillions of us use them all the time. If they were flaky, we'd all know it. And I seem to not be the only user reporting issues with the standard solutions.

Have you used the standard solutions lately and gotten reliable, accurate results?

 

[duraleigh]

While I have not used them in some time, all the standard solutions from TFTestkits are manufactured by Taylor Technologies. Sorry about that convoluted syntax in that first sentence.

 

[Rocket J Squirrel]

The other thing that comes to mind is that everyone says to test pool water within an hour of collection. Who knows how old the standard solutions are? At least a few days for shipping to customers and for delivery from Taylor to TFTK.

 

[Leebo]

The other thing that comes to mind is that everyone says to test pool water within an hour of collection. Who knows how old the standard solutions are? At least a few days for shipping to customers and for delivery from Taylor to TFTK.

Thats mostly for items such as chlorine and pH that can change drastically as it sits. Calcium really shouldn’t be effected.

 

[JoyfulNoise]

It’s helpful to keep in mind that the CH testing is probably one of the more technically challenging tests to do outside of a controlled lab environment. It is both a complexometric titration (a titration that uses different chelating agents) and it requires the removal of competing metal species (Mg2+) to get a correct value. Not to mention the color changes used are subtle and hard to see. So it’s pretty good to get within 10% of the real value using simple dropper bottles and a hand-swirled solution.

 

[Rattus Suffocatus]

The CH test is indeed a little subjective and difficult to do. I had been using a CH Titration test out of a LaMotte beer brewing water kit and the results of both were within 10% or each other so the Taylor test statistically has to be good. I am finding that I have been measuring either 200 or 220 for the last 3-4 weeks (and now it will start going up, I was testing as the 4" of rain water overfill evaporated off, and now it's on "autofill") every time... so that's +/- a drop or so. I think it's as good as it gets. Now I find the Taylor TA test to be screwy compared to another brand of TA in a test kit I have. I get the same results in both, but the other brand is easier to use. And don't ask me about the Taylor CYA test, I don't want to get in an argument about it... it's good enough too... barely...so are one brand of strips (gasp!) I have. Luckily doing TFP you don't have to check that often anyway...

Regardless, your own testing is better. The pool store's machines are capable of the reading accuracy of your TF-100 if they calibrate and handle the machines properly. Most don't care. You really can't know if they care. I suspect your reading of 425 is probably correct. Or correct enough...

What might be interesting is to take in that standard solution to the pool stores and see what they get for CH on that....

The accuracy you get in a titration kit is actually quite incredible. It's literally lab quality in most cases...

 

[Cayman]

Thanks for all of the information.

One of my concerns is if I should drain some water next week before they add the salt and turn on the SWG. Since they are adding the salt and stabilizer, I would hate to waste it.

Based on what I am seeing and reading, I think I will drain some and refill it with water from the water softener. This will dilute it down a little, but I don't want to go too far the other way, especially with the brand new finish.