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Thread: Acid additions

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    Acid additions

    Changed out the water on my tub. Always a pain because my water has has a high TA of over 250. Is there anything wrong with adding most of the acid needed in one or two doses? As it stands now I've been adding an ounce or 2 of dry acid but the PH will be back above 8 typically in 30 min. It will take at least another day of constant monitoring which is why I'm curious if I can add more acid at any given time. I know the PH would be really low but likely only for a small amount of time. Once the TA gets closer to 100 my plan would be to start slowly adding the acid again.

    Build in progress: 31x18 GI (17,336 gallons) / Diamond Brite French Gray finish / Flagstone Coping / 30ft weeping wall with 7 stations plumbed / Salt Finish Deck / Pentair EasyTouch Controls / Pentair IntelliFlo Variable Speed Pump / Pentair D.E. Filter 60sft / Polaris Automatic Pool Sweep w/ Booster Pump.

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    Mod Squad zea3's Avatar
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    Re: Acid additions

    You would really need to monitor the pH so it does not drop below 7 for a long period of time so you don't damage any of the equipment. If you have a way to bypass the heater during this time you should use it.
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    JoyfulNoise's Avatar
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    Re: Acid additions

    pH below 7.0 for any extended period of time can have detrimental impact on any metallic components as corrosion is driven by pH. If you let your hot tub run, you should be able to quickly drop the TA doing acid/aeration process.

    If you plan to use chlorine, you should consider dropping your TA to 50ppm then add 50ppm borates. The borates will help moderate the pH rise given you more time between acid additions.

    I'm curios, is there a reason you're using dry acid? While dry acid and muriatic acid have the same effect on TA, dry acid builds up sulfates in the water which are not good with respect to metal corrosion as well. I'm not saying you have to switch acid choice, just that I would use MA as it doesn't add anything I wouldn't want in the water. Your choice of course.


    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 Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Acid additions

    Quote Originally Posted by JoyfulNoise View Post
    pH below 7.0 for any extended period of time can have detrimental impact on any metallic components as corrosion is driven by pH. If you let your hot tub run, you should be able to quickly drop the TA doing acid/aeration process.

    If you plan to use chlorine, you should consider dropping your TA to 50ppm then add 50ppm borates. The borates will help moderate the pH rise given you more time between acid additions.

    I'm curios, is there a reason you're using dry acid? While dry acid and muriatic acid have the same effect on TA, dry acid builds up sulfates in the water which are not good with respect to metal corrosion as well. I'm not saying you have to switch acid choice, just that I would use MA as it doesn't add anything I wouldn't want in the water. Your choice of course.


    Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006
    I didn't know about the sulfates I'll switch to MA....already have it for the pool.

    I understand that PH below 7 can cause problems. But my question is how long does that take? If I added acid and it dropped the PH to 6 but within 60 min of aeration it was back to the 7 range would that be a problem?

    Build in progress: 31x18 GI (17,336 gallons) / Diamond Brite French Gray finish / Flagstone Coping / 30ft weeping wall with 7 stations plumbed / Salt Finish Deck / Pentair EasyTouch Controls / Pentair IntelliFlo Variable Speed Pump / Pentair D.E. Filter 60sft / Polaris Automatic Pool Sweep w/ Booster Pump.

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    Mod Squad zea3's Avatar
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    Re: Acid additions

    An hour of low pH should not be harmful. You want to avoid days of low pH levels.
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    JoyfulNoise's Avatar
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    Re: Acid additions

    Corrosion rates are not easily predicted as they depend on the types of metals found in the system as well as the other chemical species in the water. Dissolved oxygen, sulfates and chlorides all influence different forms of corrosion. If your heater is made of titanium, I would not be too concerned about a pH of 6. If it were some other metal, I might not be so cavalier with my predictions.

    As zea3 said, an hour at a pH of 6 is probably not a big deal. But you'll want to carefully monitor pH and TA while treating the water. With each acid/aeration cycle, it will take less acid each time to drop the pH.


    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 Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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