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Thread: TFP Calculator compared to Taylor chart re decreasing pH

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    brauh01's Avatar
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    TFP Calculator compared to Taylor chart re decreasing pH

    Hello,
    Working on reducing pH levels since pool opening. Not a particular problem per se, but just noticed something this morning. Entering the test results into TFP's helpful PoolMath page, I get a recommendation to add muriatic acid in the 29 to 32 ounces range. Using the acid demand test and the Taylor chart, I'm seeing something on the order of 2 quarts which is about double the PoolMath site. So, my question is, does the PoolMath site purposely lower the recommendation, especially given what might be considered a "large" change in pH?

    Reading Date pH TA PoolMath Recommendation
    4/26 8.0+ 105 32 ounces muriatic acid
    5/2 8.0 100 32 ounces muriatic acid
    5/3 8.0 90 29 ounces muriatic acid

    Using a Taylor K-2006 test kit. Water temp (not sure this is needed!) is around 60F. Solar cover installed after running uncovered 24/7 for 5 days.
    Bill
    23,500 gallon IG plaster with pebbles, Pentair FLT FNS 60 DE (160 GPM flow rate), Pentair Model 320 in-line Chlorinator, Jandy Plus HP 1.5 HP pump replaced with AO Centurian 1.5 switchless motor; Aquacal Heatwave heat pump. Method: since 2012 transitioned from "pool-stored" to TFP! Get your test kits here: TFTestkits.net correct link for pool calculator: http://www.troublefreepool.com/calc.html

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    Defgufman's Avatar
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    Re: TFP Calculator compared to Taylor chart re decreasing pH

    I quit using the Taylor chart as it was over shooting my pools needs. I found the calculator to be spot on on all chems.
    Inground 13,200 gal Vinyl, Pentair 3/4 hp pump, Pentair Sand Dollar filter, Polaris 280

    Pool School, Pool Math, CYA to FC ratio chart, Testing Kits

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    Richard320's Avatar
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    Re: TFP Calculator compared to Taylor chart re decreasing pH

    The difference is that the pH tester reads anything above 8 as 8. So it might be 9. And since you don't know for sure, neither does poolmath, so it doesn't get it right. It also isn't accurate for large changes in pH - there is this disclaimer at the bottom.
    Note: pH calculations are not exact. These numbers are only suggestive of the relative magnitude of the pH change you can expect. Small changes, +-0.4, with pH between 7.2-7.8, TA around 80-120, and Borate near zero will be approximately correct. The further you go from those ranges the less these pH changes will correspond to reality..
    The acid demand test doesn't care what the pH is now, only what it is after the drops are added.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
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    Re: TFP Calculator compared to Taylor chart re decreasing pH

    Quote Originally Posted by Defgufman View Post
    I quit using the Taylor chart as it was over shooting my pools needs. I found the calculator to be spot on on all chems.
    I had the same experience with the charts.

    Poolmath is dead on, depending on how accurate you input your pool's ACTUAL gallon size....

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    Re: TFP Calculator compared to Taylor chart re decreasing pH

    +1, Pool Math seems to put me right where I expect to be each time.
    '70s IG Vinyl 32K gal, Lazy L, Hayward SuperPump 1.5hp 120V, S240 Sand Filter W/DE
    Solar Blanket, Well Water, Borax Added, TF-100 tester. ? too cold
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    brauh01's Avatar
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    Re: TFP Calculator compared to Taylor chart re decreasing pH

    Thanks for the replies.
    Richard320, thanks for explaining the limits of the testing (and thus what PoolMath must deal with). Sounds like I can reasonably expect, after following poolmath's recommendation today, that I'll have one more round of adding acid. Helpful to know.
    Bill
    23,500 gallon IG plaster with pebbles, Pentair FLT FNS 60 DE (160 GPM flow rate), Pentair Model 320 in-line Chlorinator, Jandy Plus HP 1.5 HP pump replaced with AO Centurian 1.5 switchless motor; Aquacal Heatwave heat pump. Method: since 2012 transitioned from "pool-stored" to TFP! Get your test kits here: TFTestkits.net correct link for pool calculator: http://www.troublefreepool.com/calc.html

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