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Thread: Calcium Deposits on pool wall

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    Calcium Deposits on pool wall

    So about a week ago I noticed these white things. According to a few sources these are calcium deposits. Admittedly I was stupid and didn't put any acid in my pool for like three weeks so the pH was off the scale. Since then I've drained two feet of water and refilled the pool and then emptied 2.5 gallons of acid into the pool and the pH has been at 6.5 for a few days now. I go to scrub the calcium with a pumice stone (concrete pool) and I still cannot get the deposits off the pool. I can seem to get the majority of the hard stuff off, but there is still a white streak.

    Any clues as to how to resolve this? Thanks in advance!

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    Mod Squad Bama Rambler's Avatar
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    Re: Calcium Deposits on pool wall

    Does it fizz if you put weak muriatic acid on it? If so, you can use dilute muriatic acid to clean it.
    Dave J. TFP Moderator
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    Re: Calcium Deposits on pool wall

    I noticed these white things that kinda look exactly like this
    Is that pic of your pool or a different one? That looks like efflorescence from water seeping out under that stone wall above.
    Dave S.
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    Re: Calcium Deposits on pool wall

    If that's not your pool (that one looks unfinished?), please post a picture of what you're describing! Makes things easier when we can see what's going on.
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
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    Re: Calcium Deposits on pool wall





    Ok, attached are images from my pool. I tried to get pretty close to some of them so you could see what they look like. They are pretty much as hard as rock. The first image shows pretty much how they look all around the pool - kind of like bird droppings on a car window but inside my pool.

    The pool is an outdoor pool but is screened in if that matters. It uses a salt system.

    And I'm not sure how to apply muriatic acid directly to it since it is underwater so I'm not sure if it would fizz or not. I know since I put the 2.5 gallons of acid in the pool I've been having these weird clumps of bubbles on the top of the pool, although I'm not sure if that's due to the acid or if that would be because I drained the pool and then refilled it and now there is air in the system. I know at first there were lots of these clumps but this morning I only saw one very small one.

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    Melt In The Sun's Avatar
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    Re: Calcium Deposits on pool wall

    That is kinda funny looking, and not normally how calcium scale appears in a pool. Can you bust off a little bit of one of them and see if it fizzes with acid?
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
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    Re: Calcium Deposits on pool wall

    I can try. Like I said it's hard as a rock. Even with REALLY heavy scrubbing with a steel brush I was not able to remove it. I'll work on it and let you know

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    Mod Squad Bama Rambler's Avatar
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    Re: Calcium Deposits on pool wall

    Can you post a full set of test results and how you got them?

    You could possibly try a pumice stone on them.
    Dave J. TFP Moderator
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    Re: Calcium Deposits on pool wall

    Yes, as I said in my op I did try a pumice stone and pretty much ground the whole thing up and it still did not remove them. As far as the test results, I do not have a test kit myself as I live literally next door to a pool store so I just scooped up some water and took it over there for a few days (before, right after and three days after adding the acid). I've added some chemicals to the pool since I first went but he said my alkalinity was low and that I needed to add about 25 lbs of it (I have a 15k gallon pool) and the stabilizer was at 10 instead of 25, but that the calcium was fine after draining and re-filling the pool and adding the acid. Three days after adding the acid he said the pH was at 6.5.

    I'm sorry I can't say more, I suppose I could take another sample and have him tell me all the test results if you like.

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    Re: Calcium Deposits on pool wall

    Do a search on posts by Onbalance and "cement leaching". It may be what you have. I have a few of these white spots on the bottom of my pool and I'm certain mine are not calcium scale or otherwise caused by poor water chemistry. IIRC, Onbalance posted a link to a research paper that shows how these spots can form. It could be caused by a poor plaster job.
    9,200 gal. Gunite Luna Quartz French Grey pool with spill over spa, two fountains on tanning ledge (rarely used)
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    Re: Calcium Deposits on pool wall

    Would they suddenly just form though? I mean the pool hasn't been resurfaced in about five years and then the spots suddenly appeared within the course of two or three days. The only thing that was wrong with the pool (at least to my knowledge at the time) was that the pH was off the scale. If it was a poor plaster job, wouldn't it have appeared before now and not all at once (I don't know, I'm asking)?

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    Mod Squad Bama Rambler's Avatar
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    Re: Calcium Deposits on pool wall

    Good test results would tell is a lot but it requires a good test kit. Pool store testing is notoriously bad.

    Sorry I missed the part about already trying the pumice stone. I'd try breaking a piece off and see if it fizzes in acid as MITS suggested.
    Dave J. TFP Moderator
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    Re: Calcium Deposits on pool wall

    Quote Originally Posted by ElementZero
    Would they suddenly just form though? I mean the pool hasn't been resurfaced in about five years and then the spots suddenly appeared within the course of two or three days. The only thing that was wrong with the pool (at least to my knowledge at the time) was that the pH was off the scale. If it was a poor plaster job, wouldn't it have appeared before now and not all at once (I don't know, I'm asking)?
    Good point. I must have missed the age of your pool. My spots showed up within the first year of my pool build and some of them within just a couple of months. I also have the white spot etching that Onbalance describes. But all in all, it's not so bad for me to cause a stink with my plaster subKr.
    9,200 gal. Gunite Luna Quartz French Grey pool with spill over spa, two fountains on tanning ledge (rarely used)
    Pentair Whisperflo 2HP, Pentair CCP Cartridge 420 Sq. Ft., Polaris 280 with booster pump
    Pentair EasyTouch 4, RayPak LoNox 266k Natural Gas heater, Aqua Rite SWCG T Cell 9, Borates, TF-100 test kit

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    Re: Calcium Deposits on pool wall

    IMO Those appear to be coming from a void where the plaster didn't bond to the structure. In the void the water disolves the calcium and builds pressure and forces its way to the surface and then comes out of solution, like a stalagtite forms.

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    Re: Calcium Deposits on pool wall

    I found the post by Onbalance re: calcium nodules. The link below describes the problem.

    http://www.poolhelp.com/handouts/oB_...%20Handout.pdf
    http://www.poolhelp.com/onBalanceCal...leBulletin.pdf
    9,200 gal. Gunite Luna Quartz French Grey pool with spill over spa, two fountains on tanning ledge (rarely used)
    Pentair Whisperflo 2HP, Pentair CCP Cartridge 420 Sq. Ft., Polaris 280 with booster pump
    Pentair EasyTouch 4, RayPak LoNox 266k Natural Gas heater, Aqua Rite SWCG T Cell 9, Borates, TF-100 test kit

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    Re: Calcium Deposits on pool wall

    Ok, I managed to break some of the stuff off with a screwdrivers,dried it, then poured the muratic acid on it - DEFINITELY fizzled so I guess it means it's calcium? Next steps?

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    Re: Calcium Deposits on pool wall

    I think your link was shortened HouTex and I can't seem to click it. I did a Google image search for Calcium Nodules and can confirm that the images look exactly like what I have.

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    Mod Squad Bama Rambler's Avatar
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    Re: Calcium Deposits on pool wall

    It may not be calcium but it definitely means that acid will remove it. You should be able to rig up a pipe with maybe a funnel on the bottom and pour a little dilute acid directly on the spots. Keeping your pH in the low 7's may help dissolve them too. It would be nice to know exactly what your CH is.
    Dave J. TFP Moderator
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    Re: Calcium Deposits on pool wall

    As Carolina Pool and HouTex stated, the white calcium nodules (which is "calcium carbonate") are from delaminated sites where the plaster layer has lost the bond to the old plaster layer underneath. There is a crack below each nodule which allows the calcium carbonate material to exit from a "void" caused by the delamination and then deposit on the surface above the crack. Draining a pool will promote the loss of bonding of new plaster to old plaster.

    The best way to remove is to get some wet & dry sandpaper (either 80 or 100 grit) and simply sand off those raised calcium carbonate bumps, or just simply break them off the surface with a chisel type tool. Unfortunate, after removing them, many nodules will return or form again. When the pool water warms up, jump in the pool and remove the nodules, use a small pointed "pick" to open up the crack or hole, and then push some epoxy cement into the crack or hole to plug it up. That will stop the reformation of nodules.

    Do not make the pool water aggressive or use acid on the nodules as it will also etch and aged the surface around the nodules and make it rough permanently. Also, let's understand that this problem has nothing to do with the water balance of the pool water. The nodules will form whether the calcium, TA, or pH level is low or high. You can't stop it unless you plug the crack or hole.

    Incidently, calcium nodules are not the same thing as white spotting, soft spots, or spot etching, which are all the same plaster defect issue.

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    Re: Calcium Deposits on pool wall

    So the high pH had nothing to do with it? Interesting - given that the spots all appeared at once, I wondering why it would suddenly happen all over the pool. I know we had colder weather for a few days so the temperature of the pool water got down in he lower 50's while normally its been in the 60's during the winter (Florida pool). Do you think the colder water could have done something like shrink the pool surface and make the voids bigger thereby starting this? Just trying I find out why I never saw these before and then all of a sudden they are all over the pool.

    Thanks a bunch everyone! Looks like I need to go buy some sandpaper

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