Different Test Results

[RMcGirr83]

So for my own edification, which is now driving me completely insane, I've been doing some tests using various methods of testing:

1. Lamotte ColorQ 7
2. TF100
3. Pool Store (BioGuard)

What I can't understand is how the results can be so completely different. I can understand a 10, 20 ppm swing but some of these numbers are just crazy. The below were all done within 5 minutes of each other

Basically the TA and CH numbers vary greatly which, naturally, is affecting my CSI number. CH I'm not too worried about but I'm trying to dial in TA so my pH is more stable. Why aren't these more in line?

	Lamotte Color Q	TF100	BioGuard
FC	2.4	2.0	2
CC	0	0	0
pH	7.6	7.8	7.8
TA	64	90	47
CH	376	850	544
CYA	50	60	71
CSI	-.10	.63	"High" whatever that means

 

[PoolGate]

Your pH, FC and CYA are the important tests and your results on those counts are close. Trust the TF-100 and ignore the rest.

 

[ajw22]

TFP recommendations are calibrated to Taylor reagent testing.

Different testing methods give different results. If you developed a set of recommendations for the Lamotte tester or a specific pool store you would fit it to their testing results.

You have proved again why only Taylor testing is recommended for following TFPC methods.

 

[proavia]

Rich, you've been around here long enough to know we don't hold pool store test results in high regard.

When doing the TF-100 tests, are you holding the reagent bottles perfectly vertical and allowing the drops to fully form on the tip (not forcing the drops off the tips)? Are you using a speed stir?

Also, what is the CH and TA of your fill water?

 

[RMcGirr83]

Yeah I know not to trust pool store stuff and yes I am holding bottles completely vertical for both TF100 and Lamotte. Haven't tested my full water lately but last I recall CH was 225ish (Texas water is harder than diamonds) and can't recall what the TA was but will test it again from off the irrigation system which is before going into the house (autofill is hooked into irrigation line).
This was more of a "let's see what's what." I just can't fathom the CH results would be off that much.

 

[proavia]

How long ago was the pool filled completely? What is your evaporation rate?

Here in AZ, the water is hard also. CH around 250 and TA of 110. With evaporation rates in AZ, my CH at least doubles every year.

 

[RMcGirr83]

Pool was completed in November 2018. No idea what the evap rate is but have to imagine it's pretty high given the 95+ temperatures, wind and low humidity.

 

[proavia]

With a fill water CH of 225ish, your entire pool would have had to evaporate more than 3 times since November 2018 to get a result of 850 on the TF-100 CH test. It's doubtful that that has happened. Are you hand swirling or using a speed stir?

Using a speed stir, my CH readings dropped about 200ppm over hand swirling.

 

[RMcGirr83]

Speed stir

 

[proavia]

Well, it sounds like you are doing everything correctly with the TF-100 CH test. Have you tried the test again to see if the results match the previous test?

Do you happen to recall what the CH was in November/December?

If you have not added any calcium to the water, going from 225-ish to 850 in 8-ish months seems excessive though. Let's see what others might have to say.... @JoyfulNoise @mknauss

 

[RMcGirr83]

I'll do it again today when I get home but so far the two I've done on two separate days were pretty much in the ball park 30+ drops to get the vial to change color

 

[JoyfulNoise]

Please dilute your pool water sample 1:1 with DISTILLED water and retest. Start the test by adding 5 drops of R-0012 FIRST then add the R-0010 as-directed. Add the R-0011L dye, then titrate with the R-0012. ADD ALL DROPS OF R-0012 TOGETHER. Please report back the result.

 

[RMcGirr83]

Oh man, now I have to talk to the wife as I have zero idea where to get that around here. I'll find some though come heck or distilled water. ?

 

[IceShadow]

Distilled water can usually be purchased at grocery stores

 

[RMcGirr83]

Wife has some in the house. Says she uses it for her steam mop...who'd a thunk it.

 

[IceShadow]

Its standard use is steam irons, etc. Won't leave behind minerals as it's boiled off to make steam in a device.

 

[RMcGirr83]

LOL I understand what it is.
Distilled water is just that, water that is boiled and the steam is captured which then doesn't have any minerals in it.
Some would disagree but I'm not a complete schmuck
Thanks!

 

[RMcGirr83]

Please dilute your pool water sample 1:1 with DISTILLED water and retest. Start the test by adding 5 drops of R-0012 FIRST then add the R-0010 as-directed. Add the R-0011L dye, then titrate with the R-0012. ADD ALL DROPS OF R-0012 TOGETHER. Please report back the result.

15 drops of R 0012. 5 at onset, 10 titration

 

[JoyfulNoise]

15 drops of R 0012. 5 at onset, 10 titration

So 15 x 25 x 2 = 750ppm

Given the inherent inaccuracies of diluting without the proper chemical gear, I’m going to say your 850ppm CH is probably correct. The LaMotte ColorQ only has a range up to 700ppm and they can be very, very off when it comes to CH tests. I’m inclined to believe the Taylor tests because the process used is more accurate. The ColorQ uses absorbance to detect concentration and that can be very tricky to get right.

 

[JoyfulNoise]

Are you using a 10mL test sample or a 25mL test sample?