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Thread: Help with rough bumps on walls

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    Help with rough bumps on walls

    Over the last 2 weeks I've noticed there are tiny white/yellowish flaky bumps forming all along the tile waterline and plaster walls of our 20,000 gallon in-ground pool. The bumps are rough and with some heavy rubbing can somewhat flake off from the waterline tiles (I haven't tried rubbing it off the plaster walls). Is there any way I can remove this?

    I've talked to Leslie's Pool Supply and they told me my only hope was to use their Ultimate Scale & Stain Removal bundle for $125. I talked to other pool supply places and most said the was nothing I could do about it besides sand blasting the pool walls which could cost $800. My first guess is that the bumps are calcium deposits. Its been about a 1.5 years since we last drained the pool and I guess the high calcium and high pH finally had an effect. I spent the entire weekend shocking the pool with chlorine to get it clear again (it turned green while we went on vacation last week).

    Here are the results from the TF100 test after the water was clear enough to see through to the bottom:

    FC - 25 ppm
    CC - 0
    pH - 8.2+
    TA - 130
    CH - 160
    CYA - 100

    What should I do next? I was thinking to buy either Stain Free or Muriatic Acid but I didn't know if this was the correct move or which one to get or how much to buy. Please help as I hope my pool isn't ruined forever.

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Help with rough bumps on walls

    Welcome to TFP!

    The first thing to do is to lower your PH down to something reasonable. You should never allow the PH to go above 8.0. You are also going to want to replace water to get CYA down to something more reasonable.

    Once calcium scaling occurs there is no easy way to remove it. The recommended approach for extensive calcium scaling is to drain the pool and manually acid wash the deposits off. Sandblasting can also work, though it is a bit more complex and not commonly used. There are other approaches, but they are much less reliable than those two.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. Back To Top    #3

    Join Date
    Sep 2014
    Bakersfield, CA

    Re: Help with rough bumps on walls

    pH test results are not reliable when FC exceeds 10 ppm. However if you are getting calcium scaling with such a low CH it's likely your pH is extraordinarily high. You can use PoolMath to help you figure out how much mutriatic acid to add, but go slowly until your FC is below 10.

    Also don't ask Leslie's for any more advice, invariably they will try to sell you stuff you don't need, and will likely make the problem worse.
    Cheers, Peter
    20,000 gal, 52'x17' kidney shaped IG, Pebble Tec, IntelliPro P6E6VS4H-209L pump. Intellichlor IC40 SWG.
    300 sf Sta-Rite System 3 cartridge filter. Poolvergnuegen 4-wheel suction pool cleaner. TF-100 test kit.

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