Acid demand question

[bravowren]

Once my new pool acid demand had somewhat stabilized after 7 months, my acid demand was down to about 2 gallons a month, my routine being to add it twice a week - about a quart each time.
Last month, I decided to switch my routine to adding smaller amounts of acid every day, to keep a tighter bandwidth (+- 0.1) on my pH deviation from my 7.4 target. Since I have done so, my acid demand has been cut in half. I now put in about 4 oz. a day, which works out to a gallon a month.
Is it just my imagination, or does keeping very tight control of pH swing actually lower acid demand?

 

[VinDeeLoo]

You have lowered your alkalinity by doing it more often. With a lower alkalinity your pH has become more stabilized.


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[singingpond]

Were you running the 2 gallons per month routine for a significant number of months? Just wondering if that was a long-term stable pattern for your pool?

 

[JoyfulNoise]

Why are you targeting 7.4 as your pH? That is not typically a realistic goal in the western US due to the high pH and high TA fill water.

If you drop your TA to 60ppm and target a pH range if 7.6-7.8 (adding only enough MA to lower the pH to 7.6 and only doing so when the pH goes above 7.8), you will likely use less acid overall.

 

[bravowren]

Thanks all for your helpful replies. My 2 gal per month was for months 7-9, after the new pool had somewhat stabilized. I'm targeting 7.4 pH to balance my high CH of 500. I do not use city water for fill, but am using softened water with a pH of 7.4. I have an automatic pool cover to limit excessive evaporation.

 

[JoyfulNoise]

Thanks all for your helpful replies. My 2 gal per month was for months 7-9, after the new pool had somewhat stabilized. I'm targeting 7.4 pH to balance my high CH of 500. I do not use city water for fill, but am using softened water with a pH of 7.4. I have an automatic pool cover to limit excessive evaporation.

It's great that you have softened water to fill the pool with. However, without knowing your full test results, it's hard to know where your CSI is and how to advise. Even with a CH of 500ppm, there is typically no need to keep your pH as low as 7.4 unless you are running your TA at higher levels. Carbon dioxide outgassing is what dominates pH rise and acid demand in pools. If you hold your pH at a higher level, then the rate of CO2 outgassing is much lower and the pH rise will be a lot less.

My pool water has a CH of nearly 1000ppm. I can easily maintain my pool water in a scale free manner with my pH level kept between 7.6 and 7.8. My acid demand is less than a quart of MA added every 10-12 days and grows less and less as the weather cools.

 

[bravowren]

:It's great that you have softened water to fill the pool with. However, without knowing your full test results, it's hard to know where your CSI is and how to advise. Even with a CH of 500ppm, there is typically no need to keep your pH as low as 7.4 unless you are running your TA at higher levels. Carbon dioxide outgassing is what dominates pH rise and acid demand in pools. If you hold your pH at a higher level, then the rate of CO2 outgassing is much lower and the pH rise will be a lot less.

My pool water has a CH of nearly 1000ppm. I can easily maintain my pool water in a scale free manner with my pH level kept between 7.6 and 7.8. My acid demand is less than a quart of MA added every 10-12 days and grows less and less as the weather cools.

Thanks for the info. Base on all the feedback I got, I will try maintaining a pH of 7.6, and see how it goes. This forum has been very helpful to a new pool owner like myself.