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Thread: Why did my TA drop?

  1. Back To Top    #1

    Join Date
    Feb 2010
    Location
    San Diego, CA
    Posts
    25

    Why did my TA drop?

    Hi pool lovers!

    We've been managing my pool with BBB for 9 months and everything's been hunky-dory until today.

    I test the pool once a week and pH usually rises a bit while FC drops. Add the appropriate amount of muriatic acid and bleach and it's all good.

    Typical previous readings:
    FC 3-7
    CC 0
    TA 80-90
    CH 400-600
    pH 7.2-7.8
    CYA 30-50
    Borates 50

    Today's readings:
    FC 5.5
    CC 0
    TA 20
    CH 600
    pH <6.8 (it's quite yellow!! I'm guessing around pH 6.2?)
    CYA (ran out of reagent...it's in the mail)
    Borates 50

    Now to the questions:

    Were the **** did the TA go? This has never happened before so I'm very confused. Asked the hubby and he swears he didn't add any acid to the pool THINKING it was chlorine...

    Do I just need to add a gut load of baking soda? 11 pounds by the pool calculator??? Is it even possible that this could be right?

    Thanks in advance!
    Fiona
    11,000 gallon chlorine pool:: 48 sq ft DE filter :: IG plaster :: 1 hp Whispaflo pump :: Gas heater and Solar Panel heating

  2. Back To Top    #2
    Butterfly's Avatar
    Join Date
    May 2007
    Location
    South Carolina
    Posts
    10,045

    Re: Why did my TA drop?

    Hi Fiona,

    Quote Originally Posted by fscott
    We've been managing my pool with BBB for 9 months and everything's been hunky-dory until today.


    My suggestion is that you take your time and run your tests again to confirm before making any changes.
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

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  3. Back To Top    #3

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Why did my TA drop?

    I agree that you should confirm your readings, but having both TA and pH low is consistent with having acid added to your pool. To go from your starting TA of, say, 80 ppm to 20 ppm, that's over 20 cups of full-strength Muriatic Acid (31.45% Hydrochloric Acid) in 11,000 gallons. The pH would get to as low as 5.8 except that there should be carbon dioxide outgassing so might be at around 6.5 or so.

    If you verify the readings, then if the TA is truly 20 ppm then you would add about 15 cups (a little over 9 pounds) of baking soda to get to 80 ppm which is a reasonable level to prevent the pH from rising too much though with any such large move try adding half, mix with the pump running for an hour, then re-measure to make sure you are on track.
    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"

  4. Back To Top    #4

    Join Date
    Feb 2010
    Location
    San Diego, CA
    Posts
    25

    Re: Why did my TA drop?

    Crisis averted!

    A second pool sample was completely normal: pH 7.5 and TA 80....it's a mystery....

    Thanks for the advice -as usual TFP forum never lets me down.

    Over and out.
    Fiona
    11,000 gallon chlorine pool:: 48 sq ft DE filter :: IG plaster :: 1 hp Whispaflo pump :: Gas heater and Solar Panel heating

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