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Thread: Confused About Ascorbic Acid Results

  1. Back To Top    #1

    Join Date
    May 2015
    Moorpark, CA

    Confused About Ascorbic Acid Results

    I have a number of brown stains on my pool that I thought were the result of me letting the chlorine getting too low, pH too high, and leaves and tree berries getting in the pool when I first moved into the house. Chlorine pucks would not touch these stains. Lowering pH and SLAMing didn't do anything either. If I put Ascorbic Acid tablets on the stains, and let the tablets fully dissolve, the stain will be gone or nearly so (may take another treatment). I also noticed that the area around where I put these tablets, the blue plaster is bluer. I had the water tested for iron and copper at the pool store, and both came up zero.

    Today I decided to tackle the bigger stains at the deep end. I put two tablets on the larger stains. Sure enough, they are dissolving, and you can see a brown water trail from each stain. Further out from the stain, the plaster is turning bright blue (about a foot).

    There are no stains on the sides of the pool, only the bottom.

    So I'm confused, are these organic stains that just take some extra acid to dissolve, or iron stains?

    Today's readings:

    pH 7.5
    Cl 10.5
    CC 0.5
    CH 350
    TA 60
    CYA 60

    20,000 gallon in-ground gunite/plaster pool (1992), attached spa with spillway, Pentair Superflo 1.5 HP pump, Smith booster pump for pool sweep, Pentair 2000 DE filter, Sta Rite Max-E-Therm 400 heater, Silencer Blower 2 HP for spa, Polaris 280 pool sweep.

  2. Back To Top    #2
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Tucson, AZ

    Re: Confused About Ascorbic Acid Results

    If ascorbic acid is removing the stains and the trichlor tablets were not, then they are metallic and not organic stains. Sounds like you nee to do a full AA treatment and then start using a sequestrant. See: Pool School - Metals in the Water and Metal Stains
    Jason, TFP Moderator
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  3. Back To Top    #3
    Swampwoman's Avatar
    Join Date
    Apr 2012
    Grand Rapids, MI

    Re: Confused About Ascorbic Acid Results

    Michael, I have a vague recollection from earlier threads that you are on septic, right? Are you on a well? I believe the pool store tested zero for metals.

    Have you ever added metal sequestrant?

    I am on well, have previously had metals, and still have a few historic stains from when I opened the swamp three years ago. I have done both the AA treatment (a few times) and later switched to Metal Magic after doing the sponge test. In my case, both worked equally well for general iron staining.

    But I have a few spots that nothing ultimately resolves. Im my case, I'm vinyl and the liner is 15 years old, and I've decided to live with em until I change the liner

    But I wanted to give you a heads up that sometimes historic stains might stay, particularly if they're "2-part" types of stain.

    If you only have a few spots, not general discoloration, you might want to continue spot treatment to see if you can get there.

    I am posting a link to a tool you can use with either acid (I know, not your favorite) or metal magic to directly treat lightened mine more than anything else: : Purity Pool OS Out Spot Stain Remover : Swimming Pool Stain Removers : Patio, Lawn Garden

    Hope that helps.

    One thing I haven't tried with it but that might work is to load the tool with AA and let it dissolve on the stain for a long period of time.

    If you could post a pic of the pool overall and the specific stains we might be able to assist further.
    In ground vinyl Grecian, 24k gal, Hayward 220t sand filter, VGreen VSP 165, Hayward SWG, Raypak NG 265k heater, dolphin m4.
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