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Thread: oxalic acid clumps at bottom of the pool

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    oxalic acid clumps at bottom of the pool

    I treated my stains with oxalic acid and it was an ordeal due to the amount of staining. Anyway, the best way to remove the worst staining from the deep end was to just throw clumps of oxalic adding in. Wrong! I have no stain but after two years I still have that hard oxalic acid clump spots. I have tried tubing muriatic acid to the clumps, bleach and excessive brushing and still its like chipping away at ice sculpture. how do i get rid of this clumps?

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    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: oxalic acid clumps at bottom of the pool

    Welcome to TFP!

    We normally recommend using ascorbic acid as the reducing agent to remove metal stains and then an HEDP-based metal sequestrant to keep the metal ions in solution to prevent re-staining. Take a look at the thread Oxalic Acid Treatment and Calcium Oxalate Worries which gives one reason why we don't recommend using oxalic acid as it can precipitate as calcium oxalate if too much is used. However, it was powdery clumps and not hard as you describe. So unfortunately I don't know what happened in your particular pool and don't have a recommendation for removing it, especially since you already tried Muriatic Acid which would have been my first suggestion. Did you use a spot dosing tool for the acid such as this one?
    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: oxalic acid clumps at bottom of the pool

    Ascorbic acid even after several treatments during two seasons failed to touch my staining. I will try a tool I was just using a long PVC pipe.

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    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: oxalic acid clumps at bottom of the pool

    Did you have copper stains? Ascorbic acid works better on iron stains. For copper, oxalic acid usually works better, but has the side effects I noted.

    I would have thought that a long PVC pipe would have worked, but with the tool you can hold the acid in one place more easily and the acid will remain concentrated as well. Keep us posted.
    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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