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Thread: New plaster stains

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    New plaster stains

    Hey folks....here's my problem and I could use your help.

    Last April I had my pool re plastered with 100% quartz/sand mix. Not long after we started to notice a stain or mottled pattern showing up on the entire pool surface, not just in localized areas. My water has been perfectly balanced since the re plaster. I now find myself in an uncomfortable battle with the contractor who refuses to take 100% responsibility. The water has been tested for metals, there are none and now he wants to try a full pool acid wash....lower the pH and run a circulating pump for a few days. I'm not convinced this will do much.

    I have done some reading which indicates the real problem may be moisture trapped behind the plaster due to poor curing or bad mix. The contractor refuses to believe this is possible.
    Please take a look at my picture which was taken on the steps in shallow end but indicative of the entire surface, and give me your thoughts. Anyone else had this problem?

    Thanks so much. I have been using this forum for maintenance since the re plaster last spring and my water has never looked better. Here are my numbers:

    FC 5
    pH 7.6
    TA 100
    CH 500+ (through the roof)
    CYA 50
    Borate 50

    Also, I have been using acid like crazy since April. I understand it's normal for new plaster but it's been over 6 months now and still using lots to keep pH down.
    Attached Images Attached Images

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    Richard320's Avatar
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    Re: New plaster stains

    That looks like Calcium Scaling to me. Very similar to my pool. Tell me, does it look worse in the early morning or after dark with the lights on, but seems to disappear in full sun? That's what mine does. You'd think that Calcium would be movie-star-smile white, but it tends to be more greyish. I've almost gotten rid of it in the spa, by scrupulously maintaining the pH and scrubbing it with a wire brush while soaking. The pool steps are almost clear of it. The pool walls are not so easy to scrub.

    As an aside, my pool uses acid at an amazing rate, and it's not new plaster. Even now, with colder water, no use, and hardly any refilling, it still takes about a quart a week.
    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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    Re: New plaster stains

    Quote Originally Posted by caljw
    My water has been perfectly balanced since the re plaster.
    :
    CH 500+ (through the roof)
    The high CH along with your other numbers could lead to calcium carbonate scaling if the pH got high and this does not seem balanced. With CH of 500 and the numbers you gave, the saturation index is around +0.2, but if the CH were really closer to 1000 and the pH got to 8.0, then the saturation index would be +0.7. The pH will be higher near a curing plaster surface.

    Do you have fill water that is high in CH or was a lot of CH added on startup or did it increase from the plaster curing? In this thread you noted that the CH was 260 ppm so the CH has apparently increased dramatically in 5 months. Though the CH does increase from plaster curing, it shouldn't increase by that much.
    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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    Re: New plaster stains

    Geek....yes the CH has dramatically increased since re plaster....it is possible the pH has hit 8.0 at times, as I mentioned it has been an ongoing battle to keep it down....
    Both you and Richard mentioned scaling...my surface is smooth, wouldn't scaling cause roughness?
    Also, my contractor...the biggest and best known here in town...said he has never seen this before. If it is scaling would that be so foreign to him?

    Thanks for your input.

    cal

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    Richard320's Avatar
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    Re: New plaster stains

    Quote Originally Posted by caljw
    Geek....yes the CH has dramatically increased since re plaster....it is possible the pH has hit 8.0 at times, as I mentioned it has been an ongoing battle to keep it down....
    Both you and Richard mentioned scaling...my surface is smooth, wouldn't scaling cause roughness?

    cal
    Mine is smooth. I haven't let it keep growing long enough to become sandpaperish. At the moment, I'm pumping out some water on the lawn, I'll take a picture of the dry wall complete with stains, so you can compare, and post it a bit later.Here's the worst section of the spa wall:[attachment=1:llxg4gkd]Dsc01362.jpg[/attachment:llxg4gkd]

    and the side of the pool:[attachment=0:llxg4gkd]Dsc01360.jpg[/attachment:llxg4gkd]
    Attached Images Attached Images
    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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    Re: New plaster stains

    Richard...your right it looks just like my problem. How did you determine it was calcium scaling? And why the heck wouldn't my contractor know that?
    Good luck with your fix...I'd sure hate to have to take a metal brush to my new plaster.
    Thanks very much for taking the picture.
    cal

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    Re: New plaster stains

    Quote Originally Posted by caljw
    Richard...your right it looks just like my problem. How did you determine it was calcium scaling? And why the heck wouldn't my contractor know that?
    It's just that we have seen lots of pools with similar presentations. After a while, you know it by sight and your CH levels and history just confirm it. As for why your contractor wouldn't know that, I am not sure. But contractors do tend to vary a great deal from one another when it comes to experience and knowledge. What I can say about TFP is that collectively, we see hundreds more pools and pool problems that are brought to our attention on this forum per year than your contractor probably does in the same span of time.

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    Re: New plaster stains

    Cal-

    It does look like scaling, and you know how hard our water is. There really isn't any contractor that is going to take 100% responsibility for your pool, as it has not been in their care for 100% of the time since it has been redone. High pH is a symptom of new plaster, and it is the responsibility of the pool owner to maintain proper chemical levels on their pool, regardless of demand.

    That's the bad news. I made a phone call for you earlier today, and I will hang with this and try and get you some help (Disclaimer: No, I did not do the work here; I'm just trying to help ). I know the product that was installed (and you know I know the contractor as well), and you went with a stand up outfit, so I am sure there will be help and assistance, as they do not run from their customers. I believe that you will have to take on some of the responsibility, since the pH is out of "range", as well as your CH, but they should be able to make it look good for you and make you happy.

    If you still have my number, give me a call and we can talk. If you don't, PM me and I will get it to you again. I'm sure they would love to have you in their "happy camper" group, and I don't mind helping!

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    Re: New plaster stains

    Bruce...thanks...I was hoping you would chime in. PM sent.

    Cheers

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    Richard320's Avatar
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    Re: New plaster stains

    Quote Originally Posted by caljw
    Richard...your right it looks just like my problem. How did you determine it was calcium scaling? And why the heck wouldn't my contractor know that?
    Good luck with your fix...I'd sure hate to have to take a metal brush to my new plaster.
    Thanks very much for taking the picture.
    cal
    I think it's just one of those things you learn and never forget. Who can't identify ammonia or formaldehyde just by a whiff of 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!

  11. Back To Top    #11

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    Re: New plaster stains

    As a former pool plasterer, I am convinced that the pictures of above pools and their discoloration are not from calcium scaling. The smoothness of the plaster surface is evidence that it is not calcium scale. The (smooth) dark gray color of the white plaster is caused by excess calcium chloride added to the plaster mix, and/or may be due to overly hard, late, and dry troweling. And the light or white spotting is from excess water added while troweling and improper troweling. Excess water causes the plaster surface to become soft, weak, and porous. Over time, these areas begin to deteriorate and lose more soluble cement material (even in balanced water) in time, and turn lighter in color and appear to be very white and will remain very smooth to the touch. Furthermore, the addition of excess calcium chloride to the plaster mix will dissolve into the pool water and increase the calcium level. And the porous and weakness of the plaster surface (due to improper plastering practices) also allows more calcium to be dissolved (leached) out which also increases the CH level. Not because it is normal to do so.

    I seriously question that the plasterer hasn't ever seen that problem before. This occasional plastering defect and problem has been occuring for more than 25 years. All plasterers should know about it by now.

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