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Thread: I am getting incorrect results with PoolMath

  1. Back To Top    #1

    Join Date
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    I am getting incorrect results with PoolMath

    My levels are:
    FC 7
    pH 8.0
    TA 70
    CH 1075
    CYA 80
    Salt 3400
    Borate 0

    When I enter a pH target of 7.6 the PoolMath says to:
    Add 5.1 oz of 31.45% muriatic acid

    However, if I go to bottom, Effects of adding chemicals:
    it says that Adding 5.1 oz of 31.45% muriatic acid will
    lower pH by 0.18 and lower TA by 3. which would only take pH to 7.82

    if I enter 11 oz instead, it says it will:
    lower pH by 0.39 and lower TA by 6.4.

    I know from prior times adding acid that the 11 oz number will take my pH to 7.6 which is where I want it.

    Or am I not using this right?
    6640 gallon outdoor in-ground 8x26 pebble pool, 3'-5' deep, Pentair IntelliFlo Variable Speed pump, Jandy CL580 Cartridge Filter, Jandy AquaPure 1400 SWCG

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    Mod Squad jblizzle's Avatar
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    Re: I am getting incorrect results with PoolMath

    The top takes your TA and borate level into account. The bottom does not. Do you have your TA set at the top?

    Any chance your acid is not 31% and is instead the half strength stuff that a lot of places are now selling?
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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  3. Back To Top    #3

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    Re: I am getting incorrect results with PoolMath

    My TA is set at the top. All my numbers above are plugged in.

    The jug says it is 31.45%.
    6640 gallon outdoor in-ground 8x26 pebble pool, 3'-5' deep, Pentair IntelliFlo Variable Speed pump, Jandy CL580 Cartridge Filter, Jandy AquaPure 1400 SWCG

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    duraleigh's Avatar
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    Re: I am getting incorrect results with PoolMath

    Check your input, Isaac, the error is not in poolmath.........it's been around a long time
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  5. Back To Top    #5

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    Re: I am getting incorrect results with PoolMath

    I have attached a screen shot. Here you can see it is recommending to add 5.1 oz of acid. But at bottom effects of adding 5.1 oz only lowers pH by 0.18.
    poolmath1.jpg

    - - - Updated - - -

    Here is the screenshot where I change it at bottom to 11 oz. That says it will lower by 0.39 which should take me about to the 7.6 target I want.
    poolmath2.jpg
    6640 gallon outdoor in-ground 8x26 pebble pool, 3'-5' deep, Pentair IntelliFlo Variable Speed pump, Jandy CL580 Cartridge Filter, Jandy AquaPure 1400 SWCG

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    jtaves85mcss's Avatar
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    Re: I am getting incorrect results with PoolMath

    Although there is not enough resolution for me to enlarge the attachments and read, I get the same numbers as Issac, top versus bottom (5.1 oz and 11 oz) using his general parameters.

    I will say the top calculation has always given me the measure I need to get the desired Ph.
    Pool: IG 22k- 16x32 clipped corners- vinyl liner, w/ a great board. Built in 3/99, new to me 2/2011.
    Equip: Hayward 3600 DE filter, Hayward CL-200 Chlorinator (empty since 7/5/2013).
    K-2006 Test kit with Speedstir
    Located in Cincinnati, OH. TFP lurker since 9/2011, BBB interested since 5/2012 and converted 7/2013.

  7. Back To Top    #7

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    Re: I am getting incorrect results with PoolMath

    I have noticed the same discrepancy between the top and bottom
    22K Gal, Chlorine, IG, Pebble Sheen Plaster, Jandy 60Sq Ft DE Filter, Intelliflo 3HP VS pump with SVRS, Rainbow 320 Chlorine Dispenser
    Other Equip - Jandy PDA PS6, Jandy LRZ400 Heater, Polaris 280 vacuum
    Features - Spa with fountain that empties into pool over waterfall spillway and separate table rock waterfall, Pool gets full sun until later afternoon and then partial sun
    Pool completed and filled 6/28/13

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    Mod Squad jblizzle's Avatar
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    Re: I am getting incorrect results with PoolMath

    The top should be more accurate ... the bottom makes some assumptions for the pH calculations (as is noted in that section).
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  9. Back To Top    #9

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    Re: I am getting incorrect results with PoolMath

    Assuming you put your 6700 gallon pool size into PoolMath, the 5.1 fluid ounces of 31.45% hydrochloric acid is approximately correct. The precise answer using the Pool Equations spreadsheet is 6.6 fluid ounces. PoolMath uses tables to approximate the calculation since pH calculations are complex.

    The amount of acid indicated needed in the "Effects of adding chemicals" section does NOT use your entered TA number and instead assumes an 80-120 ppm TA range. In this case, it assumes it takes 11.1 fluid ounces to drop the pH from 8.0 to 7.6 (i.t. by 0.4 units) and you would get this if the TA were around 120 ppm. This particular section could probably be improved somewhat.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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