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Thread: The Variability of Testing Results from Different Test Kits

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    Join Date
    Jun 2008
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    Thornton, PA
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    The Variability of Testing Results from Different Test Kits

    Folks-

    I am not at all sure how to post values from a spread sheet but last summer when my PB was calling into question my testing efficacy -to include the veracity of the mighty TF-100, I did a little experiment. I tested the same exact sample of water at 4 other local pool stores -all within 1.5 hours of sample collection just to see how much variability there is among the different testing methods. Once collected and recorded I identified statistical outliers from the other testing methods. The tests ranged from my TF-100, to a Taylor kit, to BioGaurd -Strip Reader, to WaterLink Express to an unnamed Strip evaluation.

    Net net, the TF-100 did a great job, with only the CH being slightly out of whack (+10%) from the others.

    Here's the data, maybe someone knows how to make this present better?

    Testing Source Self Carlton WC Anthony/ Sylvan Elam Pools WC Aquavita Pools Raw Average Average (minus outliers)
    Date 06/06/09 06/06/09 06/06/09 06/06/09 06/06/09
    Free CL 4 5 4.3 4 4 4.26 4.08
    Combined CL 0.2 0 0.1 0.1 0 0.08 0.08
    Total CL 4.2 5 4.4 4.1 4 4.34 4.18
    pH 7.2 6.6 7.4 7.2 7.2 7.12 7.25
    Total Alkalinity 70 59 40 90 80 67.8 69.67
    Calcium Hardness 440 400 360 410 400 402 403.33
    CYA 30 150 15 35 40 54 30
    Temp 78 78 N/A N/A N/A 78 78
    Salt 3300 3300 N/A 3100 N/A 3233.33 3300
    Test Method TF-100 BioGaurd -Strip Reader WaterLink Express Taylor Reagents -full battery Strip evaluation

    I thought it was interesting, maybe you will too.

    Dan
    28K Gal. 802 Sq Ft., Free Form, IG, Gunnite with Midnight Maui Hydrazzo Carlton Pool. Exposed Aggregate Decking. Jandy DE Filter, 1.5 HP Jandy Pump, SWCG. Zodiac 380 pressure-side cleaner. Completed Construction: May 2008.

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    Mod Squad JohnT's Avatar
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    SW Indiana
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    Re: The Variability of Testing Results from Different Test Kits

    It is interesting. It actually tracks better than I would have expected. Since TA and CH are +/-10ppm by their nature, those numbers aren't too far out, but the one pH of 6.6 is a problem.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Join Date
    Jun 2008
    Location
    Thornton, PA
    Posts
    76

    Re: The Variability of Testing Results from Different Test Kits

    Yeah, the pH of 6.6 was from the Bio-Guard automatic strip reader system.

    Dan
    28K Gal. 802 Sq Ft., Free Form, IG, Gunnite with Midnight Maui Hydrazzo Carlton Pool. Exposed Aggregate Decking. Jandy DE Filter, 1.5 HP Jandy Pump, SWCG. Zodiac 380 pressure-side cleaner. Completed Construction: May 2008.

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