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Thread: Why am I still seeing scale?

  1. #1
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    Why am I still seeing scale?

    Day after day and week after week I getting scale popping up all over the pool. Sometimes it's in the form of little white dots, other times it looks almost like an icicle dripping down the wall. It seems to be mostly confined to the top few feet of water, but sometimes appears deeper down.

    Background:

    - Saltwater pool, gunnite finish
    - This is the second year that it's been opened.
    - When the pool was opened this spring, I had a massive scale problem which I beat back with two no-drain acid washes
    - The first year it was opened, there was no scale issue at all
    - for the two years it's been opened I've been fighting the raising pH by using nearly a gallon of muriatic acid a week

    Here are my latest numbers:

    FC 2
    CC 0
    TC 2
    PH 7.2 (it was around 8 before adding acid)
    T/A 60 (I finally got it down from around 210 early this year)
    CH 550

    Is my high CH a factor here?

    Is the scale just a side effect of the young pool still curing or is something more sinister going on?

    Also, should I start using scale inhibitor or some other type of treatment?

    Thanks!
    Bart
    700 sq. ft./30,000 gal, gunite pool; 48 SF DE filter; 1.5 HP pump; Salt Water Generator; Solar Heat

  2. #2
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    Re: Why am I still seeing scale?

    Your high CH is indeed a factor but your pH is a bigger factor.

    Never let your pH get to 8. Now, keeping it at 7.0 - 7.2 may help redissolve some of the scale. Do not go below 7.0 and monitor it EVERY day to keep it below 7.4.
    Dave S.
    Site Owner 42k vinyl and concrete pool, 1.5hp pump, 140gpm filter, No SWG
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    TFTestkits , PoolMath , Pool School

  3. #3
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    Re: Why am I still seeing scale?

    Thanks Dave!

    One of my problems is that the pool is at a weekend place which means I can only tinker with it Saturday and Sunday. The good news is that I'll be there for the next 5 days in a row, but that's unusual.

    Do you think the gunnite is still curing? It was poured/filled in October of 2011.

    What about scale inhibitors? Worth the money?

    Thanks!
    Bart

    PS - I just bought some replacement test chemicals from you.....didn't notice your signature until today but I recognized the "duraleigh" in the email. THanks!
    700 sq. ft./30,000 gal, gunite pool; 48 SF DE filter; 1.5 HP pump; Salt Water Generator; Solar Heat

  4. #4
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    Re: Why am I still seeing scale?

    Thanks for your business.

    The gunite may be curing a little but not too much by now.

    I don't know what's in scale inhibitor but I wouldn't use it. Just keep your pH where it belongs. How low does your pH comparator block read? If it reads 6.8 at the lowest, you are safe to go to 7.0....no lower.

    You will have to think of some way to keep your pH down while you are away. The high pH is almost surely what caused the issue and holding pH down at the sfest low possible (7.0) may very well cure it....at least stop anything further.
    Dave S.
    Site Owner 42k vinyl and concrete pool, 1.5hp pump, 140gpm filter, No SWG
    TFTestkits owner
    TFTestkits , PoolMath , Pool School

  5. #5
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    Re: Why am I still seeing scale?

    My pH block goes to 6.8.

    What do you think is causing the pH rise? The SWG?
    700 sq. ft./30,000 gal, gunite pool; 48 SF DE filter; 1.5 HP pump; Salt Water Generator; Solar Heat

  6. #6
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    Re: Why am I still seeing scale?

    What do you think is causing the pH rise? The SWG?
    Absolutely...nature of the beast.
    Dave S.
    Site Owner 42k vinyl and concrete pool, 1.5hp pump, 140gpm filter, No SWG
    TFTestkits owner
    TFTestkits , PoolMath , Pool School

  7. #7
    Mod Squad zea3's Avatar
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    Re: Why am I still seeing scale?

    Test the CH level of your fill water. If it is below 200ppm then a partial drain and refill will help, along with keeping the pH low. If you can visit only on weekends, first thing test and balance pH and make sure the returns are directed downward. Do not run any fountains or waterfalls. Water features that break the surface/churn the water at the surface raise the pH.
    TFP Moderator
    Helpful links: TF Test Kits,TFP Pool School, PoolMath
    Vogue 21" round AG, Pentair 1 hp 2 speed pump, 36 sq ft DE filter, Hayward S180T 150# sand filter, Houston, Texas
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  8. #8
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    Re: Why am I still seeing scale?

    Thanks zea!

    My jets go straight out of the wall (non-adjustable) and I don't have any water features. I did however spend the last few weeks aerating the pool with a hose to bring the T/A down to an acceptable range. I was hoping the pH would stablilize when that process was complete, but so far that hasn't happened.

    And what a great idea to use the test kit for my water!!!! D'oh! Why didn't I think of that?!!?? I had no idea how to get my well water tested and figured it would be very expensive so I've been resisting. It never occured to me that I already had everything I needed an arms length away.

    Thanks again,
    Bart
    700 sq. ft./30,000 gal, gunite pool; 48 SF DE filter; 1.5 HP pump; Salt Water Generator; Solar Heat

  9. #9
    Mod Squad zea3's Avatar
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    Re: Why am I still seeing scale?

    You may want to look at slip return fittings, such as this one to allow you to control the direction of flow from the returns.

    As Duraleigh said, the SWG will cause the pH to rise over time. Some folks use an automated system such as this one by pentair to deliver MA for pH control. I do not know anything about these systems myself so you may want to do some research if you are interested.
    TFP Moderator
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  10. #10
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    Re: Why am I still seeing scale?

    You are a prime candidate for borates. I'm not going to make any promises, but I will say I'm not the only one that has enjoyed the benefits of 50ppm borates.
    1. much lower pH swings
    2. scaling completely eliminated
    3. more stable TA

    You'll need a lot. I've tried both ways, and my recommendation would be to go the boric acid way. In a small pool a few boxes of Borax and a bottle or two of MA is not a big deal, but for big pools it's a pain.
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II T100 Sand Filter, CompuPool CPCS48 SWG, TF-100 test kit

  11. #11
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    Re: Why am I still seeing scale?

    Thanks for the borates suggestion! When I posted this thread, I noticed that first "borates" post and was thinking about reading it just to see what it was all about.......now I know!

    I spent they day yesterday reading that (long) thread and then emptying the entire borax stock of 3 different walmarts and one Target.

    I'm about to head out and start dumping and brushing and dumping and brushing.

    Thanks again for the tip.
    700 sq. ft./30,000 gal, gunite pool; 48 SF DE filter; 1.5 HP pump; Salt Water Generator; Solar Heat

  12. #12
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    Re: Why am I still seeing scale?

    It is likely that the white spots and icicles are actually "calcium nodules" due to either cracking or delamination of the new plaster coat, which sometimes happens on new pool plaster. This is a separate problem from the scaling issue that you are also having. It is also likely that even after removing the raised white spots, they will continue to return regardless of your water balance.

  13. #13
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    Re: Why am I still seeing scale?

    Here is a link to an article that explains why and how calcium nodules form. http://www.poolhelp.com/onBalanceCalciu ... lletin.pdf

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