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Thread: Gray chalky staining

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    Join Date
    Oct 2016
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    Andover NJ
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    Gray chalky staining

    Hi, we ran across the BBB pool approach 8 years ago when we first installed our pool, and have never looked back. Our pool has always been sparkly and gorgeous...until this summer. Last two years were not banner pool-care years, and so I got through the summer by just adding 'the usual' amount of liquid chlorine and muriatic acid. The pool still had beautiful water but this summer, we have divots in the bottom of the liner (lots of them) as if the sand is settling underneath the pool These spots are getting dark TOUGH algae (I'm assuming) in them, and if I get the dark spot off, it has a chalky gray layer (rough to the touch) underneath. I have tried everything from straight muriatic acid through a dish wand soap applicator brush, to toothbrushing (almost drowned with that attempt ) to magic eraser. If i use a hard unsharp stick like the back of a wooden spoon, I can get the dark spot to lift off but not the gray layer (sigh).

    Just ran my levels and they are a mess. I need to know what I can do in the next 3 days before we close it to possibly work on the problem across the winter while it's covered up. Anything that will maybe eat through the gray stuff while it's dormant, so to speak.

    FC 0
    CC 0 (usually around 2)
    PH 8.0+ (mid-July 7.6)
    TA 200 (180)
    CH280
    CYA 0 (mid-July 40 CYA)

    We do routinely run filter/clean baskets/brush walls down/backwash accordingly. Have a hand-me-down barracuda that does a pretty good job vacuuming. Water always feels fresh/unslimy, walls also not slimy.

    Hoping I can turn this around. IMG_1985.JPG
    Attached Images Attached Images
    Vinyl pool, ~32,000 gallons (20x40 rectangle, 3ft shallow, 8 ft deep end); Hayward system, DE

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    Mod Squad pooldv's Avatar
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    Re: Gray chalky staining

    That sounds like calcium scale. Your high TA and pH support that idea. Some dry acid in a sock will dissolve it. Maintaining your TA and pH levels better will prevent scale in the future. Keep them here, Pool School - Recommended Levels

    More about scale here, Pool School - Calcium Scaling
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    Re: Gray chalky staining

    The spots are all over the pool - bigger than a sock. Is there a safe way to 'acidize' the pool for the winter without eating through the liner? Read the calcium scaling post - will a pumice stone damage a vinyl liner?
    Vinyl pool, ~32,000 gallons (20x40 rectangle, 3ft shallow, 8 ft deep end); Hayward system, DE

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    Mod Squad Texas Splash's Avatar
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    Re: Gray chalky staining

    Hello and welcome to TFP! Well, at this 4-alarm stage of the game, with only 3 days until you hope to close, you may not have adequate time to address the stains as you would like, especially if it's calcium. You might focus your priority on some basic water chemistry:
    - Lower the pH to about 7.4-7.5 right away with muriatic acid. Re-check/adjust about every 30-45 minutes with pump on high.
    - You need CYA (stabilizer). Pick-up some granular stabilizer and use the sock-soaking method to add enough for a CYA target of 30 ppm. You should also do that right away.
    - Once you know the pH is down to about 7.4-7.5, and the sock is soaking the stabilizer, start adding some bleach. Just enough regular bleach on day one for an FC target of 3 ppm. On day two begin to increase FC to about 5-7 ppm.
    - The final day(s) the stabilizer granules should all be dissolved, so increase FC to 12 (SLAM level). Let that mix for about 24 hours. At the same time, brush very well and clean your filter once or twice along the way.

    Once that's done, begin your closing preparations. If you like to add Polyquat 60 as insurance, let the FC fall slightly from SLAM level to about 6-8 before adding. You can always attack the stains or discoloration next season. Probably not much you can do about those in the winter as that water should be mighty chilly. Buuurrrrrrrr!
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
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    Mod Squad pooldv's Avatar
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    Re: Gray chalky staining

    If you are interested in delaying closing then you can do the no drain acid bath and brush, a lot. The Zero Alkalinity Acid Treatment
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    Re: Gray chalky staining

    No drain acid bath can be done on a vinyl liner without damage?
    Vinyl pool, ~32,000 gallons (20x40 rectangle, 3ft shallow, 8 ft deep end); Hayward system, DE

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    Mod Squad pooldv's Avatar
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    Re: Gray chalky staining

    Yes, for a few days. Bypass a heater if you have one. Or you can take your CSI down to -0.9 and brush often if you want to try that first. PoolMath will give you the number. Lower your pH until it gets there. It will take a lot longer.

    Or you can close it and maintain low CSI next spring and brush to get rid of it. It doesn't hurt anything to have scale other than it being rough and algae likes to grow on it.
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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