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Thread: When can I add sequestrant ?

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    rickyislandgirl's Avatar
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    Apr 2013
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    When can I add sequestrant ?

    TA is at 180. CYA is at 35, PH is 75
    I was told that the TA and PH and chlorine need to be low in order for the sequestrant to work. Is this true?
    Thanks
    10,400k, AG 21 round, 1.0HP Waterway pump cartridge filter. TF-100

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    Re: When can I add sequestrant ?

    If the chlorine is too high, it will oxidize the sequestrant too quickly and will also oxidize ferrous iron to insoluble ferric. If the pH is higher, then the metal ions will precipitate or stain as metal oxides-hydroxides. Usually a higher TA level results in the pH rising over time, but by itself I don't see it interfering with the metal sequestrant (I presume you are trying to remove iron or copper and not calcium carbonate scale).

    So the usual sequence is to first get the chlorine to near zero and the pH low and use a stain remover such as ascorbic acid for iron stains or citric acid for copper stains. Then one adds a metal sequestrant product and slowly raises the chlorine and pH to normal levels. One continues to add metal sequestrant product at a maintenance dose each week to replenish that lost by oxidation from chlorine. Metal sequestrants that use HEDP are more resistant to such chlorine oxidation (compared to, say, EDTA), but nevertheless they still get broken down.

    The other approach to removing metal from the water is to do a water replacement after the stain is removed (i.e. after the ascorbic acid or citric acid treatment).

    Yet another approach to removing metal from the water is to use CuLator, but if that is done and isn't working for any reason then the company needs to be contacted for special procedures. CuLator is not inexpensive, but if water replacement or ongoing metal sequestrant use is expensive or cumbersome then it's an option.
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    Swampwoman's Avatar
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    Re: When can I add sequestrant ?

    +1 on Chemgeek's explanation...^just to add that each Mfg of the two recommended sequestrants has slightly different instructions. Metal Magic wants your ph to be above 7.5 when you use it, and prefers FC to be in the 1-3 range.
    Jack's Magic Pink prefers ph of 7.2.

    Your parameters will depend on which you purchase...once you buy your metal sequestrant, just follow the directions
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    rickyislandgirl's Avatar
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    Re: When can I add sequestrant ?

    Thank you
    10,400k, AG 21 round, 1.0HP Waterway pump cartridge filter. TF-100

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