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Thread: Hello and question about acid and FC

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    Join Date
    Feb 2015
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    Indianapolis/Indiana
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    Hello and question about acid and FC

    Greetings TPFers. First off, thanks to all who post here. I've learned a ton....but obviously not enough.

    Here's my deliema. Pool installed last fall, opened early April

    24k gallon, in ground vinyl, auto cover (closed 90% of the time thus far this season so very little sunlight),
    SWG. Pump runs continuously. Testing with Taylor 2006.

    My total alkalinity of fill water was over 200, pH has been between 7.5 and 7.8, calcium around 200, cya 40-50

    Had to slam the pool early May because it got cloudy (fc at the time was 1.5). I chalked it up to a beginner's mistake. It cleared nicely in a few days.

    Since that time, fc has never dropped below six. I have been dialing down the swg percentage trying to hit the 3-4 range but it just stayed high. Haven't been too worried and figured I would get it sorted out as I keep learning my pool.

    Did my Sunday testing a day late this week because of the holiday, so this was 72 hours ago.
    Fc 6.5, pH 7.8, TA 170. Figured I'd add some muriatic acid, and did so using the pool calculator with a target of 7.2
    Didn't open the cover (or test) the next two days because of rain.

    So I roll back the cover tonight, and she's all clowdy again. And so I test...and I find I have zero sanitizer.

    FC of 0. Ph 7.4 TA 140. I assume cya and calcium are the same because I have not added significant water

    It has dawned on me that one common thread with both of my clowdy episodes has been it occurs after the addition of acid. So my question is, could that be significantly affecting (consuming via an acid/base reaction) my free chlorine level? Could the acid addition be affecting my salt cell (I've been diluting in a bucket and adding into the deep end). Salt cell has been on 30% for the past couple of weeks.

    Any other thoughts on why my fc would suddenly drop from consistently over 6 for the past month to zero in less than 72 hours. Again let me stress that it was covered the entire time with zero bather load.

    So, 5 bottles of bleach are currently fighting the good fight, and my education continues.....
    24k gallon IG vinyl, AquaRite swg, sand filter, auto cover, deck jets x3, installed 10/14
    550 gallon IG acrylic spa, 3 step bromine, installed 10/14

    Taylor 2006
    Pentair OTO

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    Richard320's Avatar
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    Re: Hello and question about acid and FC

    No. Acid shouldn't affect FC readings at all.

    Just remember the mantra. "Only two things consume FC: organics and sunlight." If your pool was covered the whole time, then it must be organics - algae.

    Just to be sure.... check that bottle of acid and make sure it isn't ammonia or sodium thiosulfite.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Hello and question about acid and FC

    Thanks for the reply. It was definitely acid.

    No question it's algae. I just don't get how the balance was tipped so quickly. Admittedly I'm a novice, but one would think that even if the swg was off, and thus no maintained choline was added during those 72 hours, I could have coasted at least a couple of days in a covered pool with no bather load and a starting FC of over 6.
    My god, if these things are really that tenuous, then I have wasted a **** of a lot of money, because there is no way I'm gonna be able to maintain it. I simply cannot go out every single night and play Breaking Bad for half an hour.
    24k gallon IG vinyl, AquaRite swg, sand filter, auto cover, deck jets x3, installed 10/14
    550 gallon IG acrylic spa, 3 step bromine, installed 10/14

    Taylor 2006
    Pentair OTO

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    Patrick_B's Avatar
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    Re: Hello and question about acid and FC

    Once this lined out you won't have too. Youve just never gotten all the way clear, and or have remained on the ragged edge of trouble this whole time. Once you have a handle on it things will be really easy, especially with a SWG. Lots of us do only manual addition, and don't test every day. I promise, you will get a feel for it.
    TFP Moderator
    Essential Links:
    ABC's Of Pool Chemistry, Test Kits, SLAM Your Pool
    28K Gal IG FreeForm, CLI Quartz, Pentair 36"SF & VS Pump, Dolphin M5, Rheem

  5. Back To Top    #5

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    Re: Hello and question about acid and FC

    Thanks for your encouragement. I'm sure your right. I assumed all along I would make mistakes and learn from them. I'm just not sure what my mistake was here except not testing every day.

    Once I get this cleared, I'm gonna have to figure out how to confirm that my salt cell is working. Panel lights and read outs say it is, but how does one actually verify that?
    24k gallon IG vinyl, AquaRite swg, sand filter, auto cover, deck jets x3, installed 10/14
    550 gallon IG acrylic spa, 3 step bromine, installed 10/14

    Taylor 2006
    Pentair OTO

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    Donldson's Avatar
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    Re: Hello and question about acid and FC

    Quote Originally Posted by ElDuderino View Post
    Once I get this cleared, I'm gonna have to figure out how to confirm that my salt cell is working. Panel lights and read outs say it is, but how does one actually verify that?
    While your SWG is running measure your FC far away from the return and then take a sample straight from the return. If everything is working then you will see higher FC from your return water. Works best shortly after your SWG turns on, before the water has had time to mix, but you should see a difference regardless.
    JD - 28' Round Above Ground Pool, 17,000 Gallons. Dual speed Jacuzzi pump with cartridge filter. Dual speed 1 HP pump, Hayward S210T sand filter
    Pool School - PoolMath - HIGHLY Recommended Test Kits

  7. Back To Top    #7

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    Indianapolis/Indiana
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    Re: Hello and question about acid and FC

    I see. Thanks.

    Another thought that I've had.....I wonder if I've done the cya test correctly. Does either high TA or high FC affect the cya test?
    24k gallon IG vinyl, AquaRite swg, sand filter, auto cover, deck jets x3, installed 10/14
    550 gallon IG acrylic spa, 3 step bromine, installed 10/14

    Taylor 2006
    Pentair OTO

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