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Thread: Removing metal

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    Removing metal

    Let me start by saying that I don't have a metal problem.

    I've been reading a lot of forum posts on metals and it seems the standard response is maintain levels of sequesterant (cost $$$) but you can't actually remove the metal from the water. I've seen several posts of people trying various products that supposedly remove the metals and it seems the results range between poor and useless. Certainly metal is removable - reverse osmosis if nothing else (appreciate that removes _everything_ and lots of additives would need put back), but what about electrowinning? (Electrolysis to plate the metal out of the water)

    Has this been tried and ruled out? Is there something I'm missing about the chemistry that would prevent it from working?
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    Re: Removing metal

    The concentration of the metal ions if very low since as low as 1 ppm (mg/L) can cause staining. Saltwater chlorine generators don't seem to lower metal concentrations, but it's something we could look out for just in case it does and we didn't notice.
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    Mod Squad JohnT's Avatar
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    Re: Removing metal

    The metal that is supposed to be in the pool would be affected as well. Lights and niches for instance.
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    Re: Removing metal

    Do we have reference material for the electrical process in a SWG? I have nothing to back me up, but I thought they intentionally alternated the current between the plates to increase their lifespan. Which should result in something more neutral.

    As far as effecting the other metal parts in a pool - only if they're electrically connected to the electrolysis process. For safety reasons I would think the process would need to be run through an isolation transformer.
    IG gunite 20k Gal (estimate), Nautilus NS-60 filter (D.E.), Single speed pump (unreadable nameplate - assume 1HP) on a crappy mechanical timer.
    And a worn-out Kreepy Kraully. TF-100.

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    JayBauman's Avatar
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    Re: Removing metal

    Thermodynamically, it's easier to reduce copper (0.34V) ions than chlorine (1.34V) ions, so you might expect expect your electrolyzer (SWG) to preferentially reduce copper (or iron or silver or many other metals) onto the cathode rather than reduce chlorine ions into chlorine gas. However, it's not that simple. The extremely low concentrations of metal in a pool, combined with the low conductivity of your electrolyte (salt water) means that the metal ions never really see the cathode potential so they can pick up the electrons needed to plate out.
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    Re: Removing metal

    At the risk of causing Richard some dejavu, I found this discussion:
    http://www.poolspaforum.com/forum/in...howtopic=20137

    and this one
    http://www.sciencemadness.org/talk/v....php?tid=16144

    Added considerably to my reading list...
    IG gunite 20k Gal (estimate), Nautilus NS-60 filter (D.E.), Single speed pump (unreadable nameplate - assume 1HP) on a crappy mechanical timer.
    And a worn-out Kreepy Kraully. TF-100.

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    Re: Removing metal

    Quote Originally Posted by Desterline View Post
    Do we have reference material for the electrical process in a SWG? I have nothing to back me up, but I thought they intentionally alternated the current between the plates to increase their lifespan. Which should result in something more neutral.
    Yes, most salt cells reverse their polarity every so many hours in order to slough off any scale buildup (usually calcium carbonate). Technically, it could also un-plate any metals that had plated.
    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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