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Thread: Rate of TA decrease

  1. Back To Top    #1

    Join Date
    Aug 2015
    Location
    New Lothrop
    Posts
    2

    Rate of TA decrease

    I had high TA so I lowered it using the muriatic acid/aerate method. The first gallon brought TA down from 190 to 150. The second gallon from 150 to 120. The third gallon from 120 to 110. Is it more difficult to lower TA when its approaching the normal range than when its high? Or might I have another chemistry issue?
    32x16 in-ground.

  2. Back To Top    #2

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

    Re: Rate of TA decrease

    Welcome to TFP!

    Something doesn't make sense since the same amount of acid should lower the TA by a fixed amount. If I assume that your pool is 17,000 gallons and that you used full-strength Muriatic Acid (31.45% Hydrochloric Acid), then every gallon should have dropped the TA by 30 ppm. So you should have gone from 190 to 160 to 130 to 100. If we line these up to what you reported:

    Theory: . 190 160 130 100
    Actual: .. 190 150 120 110
    Diff.: ........ 0 -10 -10 +10

    You will notice that your measurements are within 10 ppm of theory and the error in the test is +/- 10 ppm so I'd say you just got fooled by errors that went high/low in pairs (i.e. 120 was lower then the true reading and 110 is higher than the true reading).
    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"

  3. Back To Top    #3

    Join Date
    Aug 2015
    Location
    New Lothrop
    Posts
    2

    Re: Rate of TA decrease

    Thanks chem geek! Logically it didn't make sense to me. And nothing online supported some type of law of diminishing returns. But, this is only my 2nd year of pool ownership, so I know I don't know everything yet!

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