Mar 24, 2013
69
NW GA
New pool store opened up advertising their brand-new-state-of-the-art WaterLink DataMate 10 water analyzer "accurate to 1/100th of a part per million".
I like numbers, so I figured why not have them test my water just to see if I'm interpreting my tests correctly. I mean pink or more pink or an in between shade of pink - it's all still very pink. :?

So I took a sample from below pool surface at dusk last night and let it sit in my kitchen overnight. I tested the water then took the same sample to the pool store. I'm using the Taylor K1005 test.

My FC looks like maybe a 3 or 4. They say 3.13 ppm. So far so good (except I do need to bump up the run time of my swg.)

My TC? Eh. I don't think it got any more pink but maybe. They say 3.38 for a CC of .25

pH - 7.4 vs 7.4 :whoot: (swg should bring that up closer to 7.6 by the end of the week)

"Hardness". I get CH of 120. The get "hardness" of 169. Idk what they are testing for though really.

TA. Swirling swirling swirling. My green goes to clear at 6 drops, faint purple at 7 drops, and undeniably pink at 8 drops. They say my "alkalinity" is 48.2 ppm.

CYA - I'm out of reagent but it's consistently been 70-80 ppm for me over the past two weeks. They say 106 ppm. [Maybe we should talk about what it means when the black dot disappears.]

Copper I don't test for; they say 0.4ppm
Iron I don't test for; they say 0.1ppm

Salt. My aquacheck sticks are in between 3500 and 3800. They say 4200.

I was in an admittedly bad mood stopping in on my lunch break and running late. The teen girl at the counter said I need to drain half the pool and refill to get my CYA down to 40. I said a CYA of 40 might be the goal for a pool using chlorine tabs but a SWG should be higher. She got kinda snippy with me [my perspective] and said she couldn't advise on any of the other numbers until I got my CYA down to 40 and retested.

So.
TA of 60-70-80? How do you interpret the titration colors?
Am I reading CYA too strictly? I look at the chamber through one eye like using a monocular microscope - focus through left eye but no squinting the right one. I add the solution until I can't see the edges of the black dot in the chamber. I don't go until the chamber looks solid white, but just until I'm not able to distinguish the black dot.
I don't know how they are determining salt. That discrepancy just doesn't make any sense. My numbers match exactly what pool calculator said they should be.
 
First don't trust the pool store measurements...no matter how fancy and "expensive" their equipment is, we see time and time again bad results. And 1/100 of a ppm "accuracy" (I guess it is really resolution) is just ludicrous. Even if is it that good, what is being tested does not warrant that resolution. The tool not appropriately speced for the job.

keep-it-simple said:
So I took a sample from below pool surface at dusk last night and let it sit in my kitchen overnight. I tested the water then took the same sample to the pool store. I'm using the Taylor K1005 test.
You should not hold onto a sample that long before testing...especially for FC, CC.

keep-it-simple said:
"Hardness". I get CH of 120. The get "hardness" of 169. Idk what they are testing for though really.
It is likely they are including Magnesium hardness, which is generally not important. CH is what you want...ignore them.

keep-it-simple said:
TA. Swirling swirling swirling. My green goes to clear at 6 drops, faint purple at 7 drops, and undeniably pink at 8 drops. They say my "alkalinity" is 48.2 ppm.
I'd trust yours.

keep-it-simple said:
CYA - I'm out of reagent but it's consistently been 70-80 ppm for me over the past two weeks. They say 106 ppm. [Maybe we should talk about what it means when the black dot disappears.]
Make sure you do this test with sun at your back and tube held at waist level. See:
http://www.troublefreepool.com/extended-test-kit-directions-t25081.html#p206397

keep-it-simple said:
That discrepancy just doesn't make any sense.
Pool store testing often makes no sense.
 
keep-it-simple said:
I'm using the Taylor K1005 test.

I'd recommend upgrading your kit to be able to perform the FAS-DPD chlorine test. It is by far more accurate and easy to read the results with titration compared to matching colors with the DPD test.

And if you want accuracy, FAS-DPD can measure FC and CC to the nearest 0.2 PPM.
 

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