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Thread: CSI and Cell Scale

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    Aquatica's Avatar
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    CSI and Cell Scale

    I've been finding my pools with +CSI even though balanced tend to collect some scale on the sensor while pools with a -CSI stay clean of scale.

    Is it better to be slightly on the - side than the + side with SWG's?

    I'm only talking about like 0.16 and some scale collects around the sensor. where pools with like -0.18 the cell stays clean.

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    JasonLion's Avatar
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    Re: CSI and Cell Scale

    If you are talking about SWGs where the sensor is inside the cell, that makes perfect sense. The CSI at various points inside the SWG cell is much higher. Keeping the pool slightly negative helps keep the CSI in the cell from going out of range high.
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    Re: CSI and Cell Scale

    Quote Originally Posted by JasonLion
    If you are talking about SWGs where the sensor is inside the cell, that makes perfect sense. The CSI at various points inside the SWG cell is much higher. Keeping the pool slightly negative helps keep the CSI in the cell from going out of range high.

    Interesting thanks Jason.

    Have you heard anything about the way the cell is installed. I know they say it doesn't matter with the AquaRite whether the sensor is facing downstream or facing upstream but I've been thinking I'd rather the sensor face upstream so the waterflow hits the sensor instead of gliding over and around it as it would if installed facing downstream.

    all my cells are installed now so that sensor is facing upstream. dont know if that helps keep scale from building on the sensor or not.

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    Re: CSI and Cell Scale

    A somewhat negative CSI will help prevent scale inside the SWG cell as will the use of borates since they provide strong buffering against a rise in pH which is what causes scaling at the hydrogen gas generation plate.
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    Re: CSI and Cell Scale

    Quote Originally Posted by chem geek
    A somewhat negative CSI will help prevent scale inside the SWG cell as will the use of borates since the provide strong buffering against a rise in pH which is what causes scaling at the hydrogen gas generation plate.

    Thanks Chem sounds good. only prob is I found with SWG's I never need to increase pH. Always need more acid. Once levels are balanced I only seem to use acid. would like to add some borates but most of the time I'm trying to get TA and pH down with a little acid each week until pH locks in place. then its smooth sailing from there.

    also havent got into adding borates yet but might be an add on service later but just busy trying to deal with the pools I have and we are still in a growth phase.

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    Re: CSI and Cell Scale

    Borates make it simpler to stop the PH from rising. Once you have added borates you can let the TA go down further than you can without borates, and once TA gets low enough PH locks in and everything stays stable for a long time.
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    Re: CSI and Cell Scale

    It also helps if you can keep the cell percentage to less than 50 %. This will allow any scale that accumulates while running to be removed when the cell is off. So, going with the largest cell possible helps.

    The same thing happens in hot tub heaters. Even at a slightly negative CSI, there is probably scale developing when the element is on and it redissolves when the element is off.

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    Re: CSI and Cell Scale

    Scale will almost never redissolve at only very slightly negative CSI numbers, so that won't work. Scale comes off when the cell reverses, at least most of the time. That doesn't work for the sensor, which is why scale is seen on the sensor but not the cell plates. On heaters scale doesn't usually occur, since the CSI increase inside the heater isn't nearly as high as it is inside the SWG. Scale can also come off of a heater due to thermal cycling.
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    Re: CSI and Cell Scale

    Quote Originally Posted by JasonLion
    On heaters scale doesn't usually occur, since the CSI increase inside the heater isn't nearly as high as it is inside the SWG. Scale can also come off of a heater due to thermal cycling.
    I was thinking about the heating element in an electric hot tub heater. I figured that it got hot enough to scale when it was on?

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    Re: CSI and Cell Scale

    Quote Originally Posted by JamesW
    It also helps if you can keep the cell percentage to less than 50 %. This will allow any scale that accumulates while running to be removed when the cell is off. So, going with the largest cell possible helps.

    The same thing happens in hot tub heaters. Even at a slightly negative CSI, there is probably scale developing when the element is on and it redissolves when the element is off.
    i think that effect is minimal if there at all.

    if that was any significant then there would be no point in making reverse polarity units, you'd just make cells big enough to be run at 50% all the time.

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    Re: CSI and Cell Scale

    TA and CH levels in a spa are normally much lower than they would be in a pool, resulting in lower room temperature CSI levels. The CSI increase from a spa heater is only going to be perhaps +0.2, which is normally on top of an otherwise negative CSI, so there shouldn't be any scaling. The CSI increase inside an SWG can be much more dramatic than that.
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