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Thread: Help with Calcium Nodules?

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    Join Date
    Jun 2015
    Location
    Austin/TX
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    Help with Calcium Nodules?

    I believe we have calcium nodules all over the bottom and walls of our pool. Our pool builder looked at our pool last week for a pipe leak (that's another story) and when I asked about the white spots he said they were "Calcium Nodules" and we can just scrub them off. We tried a wire brush (as he suggested) that did nothing and also tried a pumice stone and although that seems to help it does not remove completely and I can not see being able to do that all over the bottom of the pool. Is there any other options? and what causes this?

    Thank you in advance for any advice!!
    FullSizeRender (2).jpgFullSizeRender (1).jpgFullSizeRender.jpg
    plaster free form, 28000 gallons
    Salt, built in 8/2011

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    Richard320's Avatar
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    Jan 2010
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    San Dimas, CA (LA County)
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    Re: Help with Calcium Nodules?

    Welcome!

    High pH and high CH conspire together and form them.

    I've had better luck removing them using drywall sanding screen than with pumice.

    The longterm solution is to keep the chemistry balanced. What sort of test kit do you have? Have you seen Pool School - Test Kits Compared

    There are ways to slowly remove the Calcium - and I mean at a glacial pace - by careful chemistry, but without knowing you have the right test kit, I won't detail it because you won't be able to do it.
    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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    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
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    Re: Help with Calcium Nodules?

    See the thread Calcium Nodules in Pools. The cause is improper bonding of the plaster surface in a way that has created voids. These voids contain calcium hydroxide and when eventually the plaster surface gets a pinhole in it, say from movement/flexing over time, water may enter the void and the calcium hydroxide escape where it meets bicarbonate in the water to form calcium carbonate. The pH in the pool also rises as a result.

    Ironically, keeping a proper water balance to protect plaster surfaces has this problem show up more. If you had more aggressive water, then there would be less nodules formed or they would form with less calcium carbonate, but you'd also be threatening the rest of your plaster surface. So the bright side is that these nodules show you have your water at least reasonably saturated with calcium carbonate (i.e. your pH, TA, CH is likely in good shape). If you post a full set of water chemistry test results, we can confirm this.

    I got these in my pool after around 7 years (it was a new pool, not a replaster). There was also delamination. It was not a great plaster job and the pool is now 11 years old. Normally these problem are more common after a replaster job since it's harder to properly bond new curing plaster over already cured gunite or plaster.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Join Date
    Jun 2015
    Location
    Austin/TX
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    Re: Help with Calcium Nodules?

    thank you for your help, We usually take our water to the pool store for a full run down of tests about once a month. I check the cl/ph once a week. I will check this afternoon and post. after reading one of the posts we will get a better kit to do more testing at home. This is our first pool and never really got any info on how to take care of it so we have relied on our local pool store for help, we are trying to learn as we go so we are better educated on caring for our pool. Thanks again for your help. One question, you mentioned that it had to do with the plaster? does this mean we should look at getting our pool replastered? and do you know can you go from plaster to pebble-tec?
    plaster free form, 28000 gallons
    Salt, built in 8/2011

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    poolnoob.ca's Avatar
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    May 2014
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    Georgetown, ON, Canada
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    277

    Re: Help with Calcium Nodules?

    Quote Originally Posted by myflores View Post
    This is our first pool and never really got any info on how to take care of it so we have relied on our local pool store for help, we are trying to learn as we go so we are better educated on caring for our pool.
    Sadly this is the way it goes. They sell you a nice expensive pool, then dont even tell you how to maintain it, or tell you incorrect info, then you end up on the pool store merry-go-round...until the dizziness wears off and you end up at TFP
    32,000L Fibreglass Leisure Pools IG 12.5'x23'x5' Pump: AstralPools BX1 1.0HP
    Filter: AstralPools ZX-310 SWCG: AstralPools VX7T
    Heater: Hayward H250FDN Test Kit: TF-100

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