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?
Rate of TA decrease
- Thread starter suicidalbob
- Start date
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).
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).
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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