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Thread: Unexplained TA rising

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    HamburgerChef's Avatar
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    CHLORINE DROPPING TO ZERO

    I just finished my pool build (well its swim-able) and it just finished filling from well water today. 2 days total fill time. Pump and filter came online a few hours ago. While filling I used the Pool Calculator to adjust chlorine to shock levels each evening. Last evening and this evening the levels have been below detection with the TF-100 kit prior to adding bleach. There is no FC or CC. I have not yet added any CYA but plan to do so tomorrow. There is a lot of what looks like rust that has collected on the bottom of the pool. The cleaner is blowing that off the bottom tonight so hopefully it will be clean and ready to swim tomorrow.

    Is it normal for the chlorine to drop to zero from 10ppm in 24 hours? What is causing it? Sun? Iron?

    PH is 7.5 as far as I can tell.
    13,500gal AGP Matrix 24'
    Pentair Sanddollar SD-80 75GPM filter, Pentair Dynamo 1HP 2 speed pump
    Polaris 65 pool cleaner
    (20'x30" solar heater to be installed)

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    Richard320's Avatar
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    Re: CHLORINE DROPPING TO ZERO

    Quote Originally Posted by HamburgerChef
    I just finished my pool build (well its swim-able) and it just finished filling from well water today. 2 days total fill time. Pump and filter came online a few hours ago. While filling I used the Pool Calculator to adjust chlorine to shock levels each evening. Last evening and this evening the levels have been below detection with the TF-100 kit prior to adding bleach. There is no FC or CC. I have not yet added any CYA but plan to do so tomorrow. There is a lot of what looks like rust that has collected on the bottom of the pool. The cleaner is blowing that off the bottom tonight so hopefully it will be clean and ready to swim tomorrow.

    Is it normal for the chlorine to drop to zero from 10ppm in 24 hours? What is causing it? Sun? Iron?

    PH is 7.5 as far as I can tell.
    Without any CYA, yes.

    You'll lose something like 1/2 per hour in sunlight. So...10 - 5 - 2.5 - 1.25 - .63 -.31 - .15 - undetectable.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    HamburgerChef's Avatar
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    Re: CHLORINE DROPPING TO ZERO

    Thanks for the quik reply. I will pick up some from the Pool Store tomorrow on the way home.
    13,500gal AGP Matrix 24'
    Pentair Sanddollar SD-80 75GPM filter, Pentair Dynamo 1HP 2 speed pump
    Polaris 65 pool cleaner
    (20'x30" solar heater to be installed)

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    Re: CHLORINE DROPPING TO ZERO

    Quote Originally Posted by HamburgerChef
    Thanks for the quik reply. I will pick up some from the Pool Store tomorrow on the way home.
    aw, sometimes they have the best price
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    Re: CHLORINE DROPPING TO ZERO

    If you live near a Walmart, and don't despise it like I do, they also have CYA.
    John
    7 year old ~13,500 gal 24' AGP with 1.5 hp Proline pump, 150 sqft Pleatco cartridge, filled with well water with pH of about 4.5.
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    HamburgerChef's Avatar
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    Re: CHLORINE DROPPING TO ZERO

    Quote Originally Posted by JohnN
    If you live near a Walmart, and don't despise it like I do, they also have CYA.
    In my area they were the only place that carries CYA. I called the local pool store and they didn't have any.

    Me, "yes, do you carry cyanuric acid?"
    Pool Store, "What?"
    Me, "You know, cyanuric acid, like stabilizer or anything?"
    Pool Store, "We have Sulfuric Acid"
    Me, "So you don't carry stabilizer"
    Pool Store, "What is stabilizer?"
    Me, "Thanks for your help!"

    I put in CYA from Walmart and am currently waiting for one week to pass. After succesfully shocking the pool per pool school criteria here is what I have.

    Test results before CYA
    FC-10.5
    CC-0.5
    CYA probably 0
    TA-180
    PH-7.5

    Test results 24 hours after addition of CYA.
    FC-3
    CC-0.5
    CYA 10-15 too low to be sure
    PH-7.9 shouldn't this have gone down with CYA addition?

    Test result 48 hours after adition of CYA and 2 hours after addition of dry acid
    FC-2
    CC-0.5
    CYA 10-15
    TA-240 Why did it go up?
    PH-7.4

    Added more dry acid and rechecked 1 hour later
    PH-7.2

    So now the return is pointed up and is churning the water to raise PH up again. Why did my TA raise? Is it something in the CYA? Something in the dry acid? I have been using Tech Group brand 10% liquid chlorine from Meijer.
    13,500gal AGP Matrix 24'
    Pentair Sanddollar SD-80 75GPM filter, Pentair Dynamo 1HP 2 speed pump
    Polaris 65 pool cleaner
    (20'x30" solar heater to be installed)

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    Re: CHLORINE DROPPING TO ZERO

    Did you add any water to the pool recently? If so, the TA increase probably came from the fill water.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: CHLORINE DROPPING TO ZERO

    Quote Originally Posted by JasonLion
    Did you add any water to the pool recently? If so, the TA increase probably came from the fill water.
    I didn't add any water during any of these tests but it has rained several times. Probably 2" total.
    13,500gal AGP Matrix 24'
    Pentair Sanddollar SD-80 75GPM filter, Pentair Dynamo 1HP 2 speed pump
    Polaris 65 pool cleaner
    (20'x30" solar heater to be installed)

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    Re: CHLORINE DROPPING TO ZERO

    Rain normally has no effect on TA, though occasionally it will lower TA.

    It doesn't have anything to do with "during" the test. Any water added to the pool at any time between the two tests could have raised the TA, though raising it that much is unlikely even when you have high TA fill water.

    The only other plausible possibility is testing error. Try wiping the tip of the reagent bottles with a damp cloth/tissue right before doing the TA test and see if that changes the result.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    HamburgerChef's Avatar
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    Re: CHLORINE DROPPING TO ZERO

    Should I wipe between each drop or is wiping at the beginning of each reagent enough. It is probably my testing that is throwing off the results. This is my first time using the kit.
    13,500gal AGP Matrix 24'
    Pentair Sanddollar SD-80 75GPM filter, Pentair Dynamo 1HP 2 speed pump
    Polaris 65 pool cleaner
    (20'x30" solar heater to be installed)

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    Re: CHLORINE DROPPING TO ZERO

    Test results today after 24 hours of return pointed up.
    FC 3
    CC 0.5
    TA 250
    PH 8.1

    Is there a chance that alkalinity up powder from last years intex pool could be bound somehow in the Sand filter Sand? I remember last year using the test strips and questioning the TA results from them. I also recollect having a very hard time changing PH last year (more chemicals than the package called for not making a significant change) and thinking it was caused by too high TA.

    So far this year I added a total of 8.5lbs of Dry Acid (Sodium Bisulfate) and the TA actually increased. What is going on here?
    13,500gal AGP Matrix 24'
    Pentair Sanddollar SD-80 75GPM filter, Pentair Dynamo 1HP 2 speed pump
    Polaris 65 pool cleaner
    (20'x30" solar heater to be installed)

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    HamburgerChef's Avatar
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    Unexplained TA rising

    I posted this topic in the "Just Getting Started" section but still need help. My pool was installed a couple weeks ago. The filter however is used and filled with sand from last season. I had problems with TA and PH last season.

    The TA in the pool has been rising for no good reason. Initial reading was 180. The next reading was 240. The only chemicals used between these two readings were Cyanuric Acid (HTH Stabilizer Conditioner) and liquid Sodium Hypochlorite (Tech Group brand Pool Sanitizer). No water was added but did receive several inches of rain.

    So I added 8.5lbs Dry Acid (HTH Sodium Bisulfate) which lowered the PH to 7.2 and then aerated to 7.9. The next test result showed TA 250. Why would this happen? I thought Dry Acid should lower TA and PH, while aeration should raise PH without affecting TA. Is it possible that the old sand in the filter could be leaching something into the pool that is slowly raising TA?

    I added 4.1lbs of Dry acid yesterday to bring PH back to 7.5. I will check TA soon and post results.
    13,500gal AGP Matrix 24'
    Pentair Sanddollar SD-80 75GPM filter, Pentair Dynamo 1HP 2 speed pump
    Polaris 65 pool cleaner
    (20'x30" solar heater to be installed)

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    Re: Unexplained TA rising

    Topics merged. Never ask the same question in more than one place. JasonLion

    Try wiping the tip of the TA titrant dropper bottle with a damp tissue or cloth between drops while doing the TA test. Sometimes static electricity can build up on the tip and cause false high readings.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    HamburgerChef's Avatar
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    Re: Unexplained TA rising

    I tried wiping the tip on all reagents on the last test and still had TA rise. I will check the TA now and post back in a few.
    13,500gal AGP Matrix 24'
    Pentair Sanddollar SD-80 75GPM filter, Pentair Dynamo 1HP 2 speed pump
    Polaris 65 pool cleaner
    (20'x30" solar heater to be installed)

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    HamburgerChef's Avatar
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    Re: Unexplained TA rising

    Sorry for multiple posting.

    Results are TA 220. Is this a normal drop for adding 12lbs of dry acid?
    13,500gal AGP Matrix 24'
    Pentair Sanddollar SD-80 75GPM filter, Pentair Dynamo 1HP 2 speed pump
    Polaris 65 pool cleaner
    (20'x30" solar heater to be installed)

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    Re: Unexplained TA rising

    Have you tested the TA of the fill water?
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

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    Re: Unexplained TA rising

    I would expect 12 lbs of dry acid in 13,500 gallons to lower TA by about 40. That matches your test results within the precision of the test.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    HamburgerChef's Avatar
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    Re: Unexplained TA rising

    THANKS LION!!! This TA lowering will be very expensive using dry acid. Acid is $11.59 per 7lbs. Started at TA 250 minus goal of TA 80 = drop of TA 170 divided by TA 40 drop per 12 lbs of dry acid is 4.25 or 3.25 more drop add Acid Aerate cycles. 4.25 Multiplied by 12 lbs is 51 lbs. That is about $81 after tax. Is it worth it? Does it really make any difference if the TA is high?
    13,500gal AGP Matrix 24'
    Pentair Sanddollar SD-80 75GPM filter, Pentair Dynamo 1HP 2 speed pump
    Polaris 65 pool cleaner
    (20'x30" solar heater to be installed)

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    HamburgerChef's Avatar
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    Re: Unexplained TA rising

    Quote Originally Posted by Butterfly
    Have you tested the TA of the fill water?
    I haven't checked it yet but that would probably tell me if the filter is leaching or not.
    13,500gal AGP Matrix 24'
    Pentair Sanddollar SD-80 75GPM filter, Pentair Dynamo 1HP 2 speed pump
    Polaris 65 pool cleaner
    (20'x30" solar heater to be installed)

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    Re: Unexplained TA rising

    You should consider using muriatic acid. Not only is is much less expensive, it also does not add sulfates, which can (rarely) cause minor problems. On the other hand it is a little more trouble to work with (fumes).

    High TA levels cause the PH to go up fairly rapidly. As long as you can keep the PH under control, high TA isn't otherwise an issue.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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