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Thread: Acid demand question

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    Acid demand question

    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?
    38x11 IG rectangular shotcrete w/ integrated 6x6 spa, CoverPools auto cover. Main pump Intelliflo VS, Spa pump Pentair XF VS, Pentair 400KBTU heater, 520SF Cartridge Filter , Flowvis, Pentair SWG, Levelor. 10x Waterway power storm jets. EasyTouch automation, Intellibrite LEDs.

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    VinDeeLoo's Avatar
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    Re: Acid demand question

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


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    VinDeeLoo
    7600 gallons ~ AG ~ Summer Waves Cartridge C Filter ~ using pump that came with our Summer Waves 18 x 48 pool ~ Taylor K-2006 (SpeedStir & Sample Sizer) ~ no well water or water restrictions

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    Re: Acid demand question

    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?
    18' x 48" ring top pool (Summer Escapes); 5500 gallons; set up June - October, stored during winter; Intex 2500 gph pump (B size cartridge filter) Hayward 21" sand filter + 1.5 hp single speed Powerflo Matrix pump (upgrade October 2016) *** K-2006 test kit, refills from tftestkits

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    JoyfulNoise's Avatar
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    Acid demand question

    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.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Acid demand question

    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.
    38x11 IG rectangular shotcrete w/ integrated 6x6 spa, CoverPools auto cover. Main pump Intelliflo VS, Spa pump Pentair XF VS, Pentair 400KBTU heater, 520SF Cartridge Filter , Flowvis, Pentair SWG, Levelor. 10x Waterway power storm jets. EasyTouch automation, Intellibrite LEDs.

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    JoyfulNoise's Avatar
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    Re: Acid demand question

    Quote Originally Posted by bravowren View Post
    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.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Acid demand question

    :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.
    38x11 IG rectangular shotcrete w/ integrated 6x6 spa, CoverPools auto cover. Main pump Intelliflo VS, Spa pump Pentair XF VS, Pentair 400KBTU heater, 520SF Cartridge Filter , Flowvis, Pentair SWG, Levelor. 10x Waterway power storm jets. EasyTouch automation, Intellibrite LEDs.

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