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Thread: Can high chlorine cause staining?

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    Can high chlorine cause staining?

    Split by moderator from HERE. Please start your own thread and not tack on question in a sticky. Thanks, jblizzle.

    Question : I read in another post in this forum that "too much Chlorine can cause staining" ... Is that TRUE? e.g., Given the subjective nature of the test, my CYA is somewhere between 35-50. I always try to maintain around 5-6ppm of CL. But when we leave on vacation, I dump a bunch of Chlorine in the pool - bringing it up to around 10-12ppm - just so that when we return a week later there is at least 2ppm remaining & we don't go down to danger level of no chlorine ... Is this Wrong to do and possibly causing staining? If so, what do people do when away on vacation? A pool service or "pucks" ?
    30,000 Gal FIBER GLASS (over Gunite Plaster) Pool, Dolphin Nautilus PLUS Robot, (2) Cartridge Filter System (old), 1/2 HP Pump, Full Sun, Solar Heated, TF-100 Test Kit.

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    Mod Squad JVTrain's Avatar
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    Re: Chlorine/CYA Chart

    You probably don't remember but can you provide a link to the post or who told you?

    Very high levels of chlorine with low CYA levels will not likely cause staining, rather they would cause bleaching or fading of parts and materials. The longer the concentration stays high, the more potential damage. It would also degrade the integrity of plastic based parts more quickly. Using the Chlorine/CYA chart, it is safe and recommended to raise FC as much as up to SLAM level when leaving for a few days. Longer than a few days and then you can raise the FC up to SLAM level and/or use pucks. Covering the pool will also reduce chlorine demand for longer vacations. Otherwise, I've heard folks talk to a trusted neighbor and have them add set amounts of bleach for them based on usual demand while they are gone.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
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    Re: Chlorine/CYA Chart

    You probably don't remember but can you provide a link to the post or who told you?
    Yes, I would like to find that, too.
    Dave S.
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    Re: Can high chlorine cause staining?

    It's higher pH that can cause metal staining especially to plaster surfaces if the pH rises. The pH does rise when you add a hypochlorite source of chlorine (such as bleach or chlorinating liquid or Cal-Hypo or lithium hypochlorite), but it drops back down when the chlorine is used/consumed. So I suspect what you saw was about using a lot of chlorine all at once which would raise the pH and potentially risk staining. If you lowered the pH before adding the chlorine, then that risk would be minimized. If you used 50 ppm Borates for additional pH buffering, then the amount of temporary pH rise from chlorine addition would be significantly lessened.
    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
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    Re: Can high chlorine cause staining?

    The Lafayette area in California has very soft tap water and probably does not contain measureable metals. High chlorination of 12 ppm would not cause staining issues. The question is whether there is copper in the plumbing.

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