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Thread: Calcium deposits?

  1. #1
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    Default Calcium deposits?

    Is this a calcium deposit? (see attached photo).

    Before I was introduced to this site, I used Cal Hypo to deal with an algae problem. I have since been testing regularly, keeping chlorine levels up with my SWCG and pH and alk balanced with muriatic acid. I have had the pool open for 10 months, and had some growing pains with the SWCG, but seem to have a good balance now.

    My numbers this morning were:
    FC: 9.0
    CC: 0.5
    TC: 9.5
    pH: 8.2
    Alk: 130 (I have since added 1 gal muriatic acid-will retest in a couple hours)
    Cal: 420
    Cya: 60
    Temp: 78
    Salt: 3200

    My typical readings throughout August were:
    FC: 8.0
    CC: 0.5
    pH: 7.8
    Alk: 100
    Cal: 420
    Cya: 65
    Temp: 83
    Salt: 3200

    Can anyone tell me just what the build-up is (in the photo) and how I should remove it?

    Thanks,
    Larry
    Attached Images
    Last edited by halefmly; 09-04-2006 at 09:17 AM.
    Larry

  2. #2
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    Smile Re: Calcium deposits?

    Hi Larry,

    I was hoping to see someone else respond to this so they could better explain the actual chemicals that are in your deposits...there's an explanation for what you're seeing...efflourescence???

    Anyway, I have the same deposits that form underneath my rock waterfall and seem to come down the grout lines, although they do exist on the tile, as well. A dilute solution of muriatic acid, about 1 part muriatic acid to 4-5 parts water sprayed onto the surface and then brushed with a hand brush seems to do the trick for me. The stuff will fizz and bubble on the surface as it's clearing up the deposits. Easy to rinse off with pool water right after working in an area, too. When you're done, you can dump the excess solution (shouldn't be much) into the pool where it will work to lower your pH. When working with even a dilute mixture of muriatic acid, I wear rubber gloves and eye protection...quite the site in the pool .

    I've only had my pool 3 months, SWCG about 1 month, and it seems as if I have fewer deposits if I really keep an eye on my pH. My pool's happy at 7.5. When my pool was first filled and the pH was over 8.2, the deposits built up right away, within that first week. Even at 7.8 or just below, the deposits came up fairly quickly. Now, at 7.5, it's several weeks before I feel I have to clean them off.
    Sandy
    15,600 gallon, screened 15x30 IG plaster sport pool with 6x8 tanning area, Aquarite SWCG, Hayward cartridge filter, Polaris 280 cleaner

  3. #3
    chem geek is offline PF Supporter Whibble Konker chem geek 4 stars chem geek 4 stars chem geek 4 stars chem geek 4 stars
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    Default Re: Calcium deposits?

    Larry,

    The deposits may be calcium carbonate because the combination of high CH, high TA, and high pH can lead to this scaling. Your typical readings through August had a saturation index of about 0.5 which isn't extraordinarily high (most people don't see cloudiness until 0.7 or 1.0), however your "this morning" numbers had a saturation index close to 1.0. I would have thought that the water would have become cloudy before you saw such deposits, but perhaps the evaporation of the water above the water line made the concentration much higher thus precipitating calcium carbonate.

    As Sandy suggested, dilute acid will dissolve this scale. You should try and keep your pH down closer to 7.5 though you may have trouble doing this with your TA level at 130. If you find your pH rises frequently and you are always adding acid to lower it, then try lowering your TA level significantly down to 80 or below (using Ben's Lowering Your Alkalinity procedure) and see if this improves your rising pH and required acid addition. See this thread for more detailed info about possible sources of rising pH in SWCG pools.

    Richard

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    Smile Re: Calcium deposits?

    Sandy and Richard,

    Thank you both for the replies. I will use your suggestions to get the scale removed, and also to get the TA reduced.

    I have been reading the thread with Ben's method for reducing TA. I have a spillover from the spa into the pool, and also a fountain water feature in the spa. Will those alone create enough bubble action for the outgassing, or should I run the spa's air pump as well?

    Larry
    Last edited by halefmly; 09-23-2006 at 08:57 AM. Reason: to put the a s s back in "outg***ing"
    Larry

  5. #5
    chem geek is offline PF Supporter Whibble Konker chem geek 4 stars chem geek 4 stars chem geek 4 stars chem geek 4 stars
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    Default Re: Calcium deposits?

    Larry,

    For fastest results, run the spa's air pump. The more aeration the better, unless you want to wait longer for the pH to rise (and TA to drop when you add acid). You should also make sure you get good mixing between your spa and pool water -- otherwise the pH rise, add acid, pH/TA drop process will happen much more in your spa instead of your pool.

    Richard
    Last edited by chem geek; 09-04-2006 at 10:53 PM.

  6. #6
    KurtV is offline Registered+ Widget Weaver KurtV 0
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    Default Re: Calcium deposits?

    That looks like, as DawnDenise said, efflorescence. That leaches though (or "flowers" if we want to be true to the root of the word) from the concrete/gunite, as opposed to being deposited by your water. Not much practical difference when it comes to removing it, but all the water chemistry in the world won't prevent it if it is efflorescence.

    This is pretty common, as I understand it, on raised bond beams and exposed gunite walls. I get it on the back side of the negative edge, even through the tile.

  7. #7
    chem geek is offline PF Supporter Whibble Konker chem geek 4 stars chem geek 4 stars chem geek 4 stars chem geek 4 stars
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    Default Re: Calcium deposits?

    Larry,

    Both Sandy (dawndenise) and KurtV are right about efflorescence (which is why it's so great to have a forum with multiple answers). Your water chemistry is still on the scaling side, but since you don't have cloudy water this isn't something to worry about, though as I said, lowering your TA should help lower your pH rise and acid demand. At any rate, if you make a dilute acid solution using Muriatic acid to clean up the deposits, be sure to remember the rule I learned in chemistry class, "if you're doin' what you oughta, add the acid to the water." The reason is that dilution of acid generates heat so doing it wrong by pouring water into acid can generate enough heat to cause water droplets (with some acid now in it) to boil and splatter (into your face).

    Richard

  8. #8
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    Default Re: Calcium deposits?

    Also for maintenance purposes - you probably want to keep your PH closer to 7.4 than 7.8. The SWCG generator will quickly get your PH too high - I try to keep my PH between 7.2-7.4.
    Completed 8/21/06
    14,000 gallon 3'-6' concrete pool with Diamond Brite
    Spa with spillway
    250K BTU gas heater (for spa)
    SWCG - Aqua Rite
    Hayward Super II Pump - Cartridge filter

    See pictures here http://www.philsimmons.com/family/ga...mages&keyword=

  9. #9
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    Default Re: Calcium deposits?

    Many thanks to all of you for the advice. I will post here as I make progress against the efflorescence and also the Alk.

    Larry
    Larry

  10. #10
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    Default Re: Calcium deposits?

    Well, I needed to use a scraper in conjunction with the acid/water solution, but the efflorescence is now gone. I have been using the aeration method in an attempt to bring down the TA, and it has been hovering around 90 for some time, but today, after a weekend of plenty of pool use and splashing, it is now down to 80.

    FC: 14.5 (I have just lowered the SWCG from 45 - 25%)
    CC: 0
    pH: 7.5
    Alk: 80
    Cal 470 (that is higher than my usual 420 - I'll recheck)
    Cya: 60
    temp: 83
    Salt: 3000

    Thanks to all who have given advice and suggestions in this thread.
    Larry
    Last edited by halefmly; 09-10-2006 at 08:01 PM. Reason: spelling
    Larry

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