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Thread: SWCG and CYA

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    SWCG and CYA

    How is it that CYA disappears over the summer with a SWCG, yet most literature states that CYA never breaks down and can only be decreased thru removing and adding water. I realize some gets lost to splash out and rain, but a SWCG pool and a Dichlor pool put side by side will show a marked decreased of CYA in the SWCG pool.

    Is it possible that the electrolysis in the cell breaks down the acid to a alkaline slowly over a month or two?

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    susa's Avatar
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    Re: SWCG and CYA

    It may be possible for the CYA to be converted to ammonia by bacteria if your FC levels are low. Keep FC between 3-5 and CYA around recommended levels. Having 50 ppm borates helps too as it leaves less for microbial action.

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    Re: SWCG and CYA

    the SWG doesnt deplete teh CYA through electrolysis or any other means.
    CYA can be broken down to ammonia but that typically happens over a long period of time while the pool is closed for the winter.

    Backwashing frequently will deplete the CYA or water loss by means of overflow and dilution due to heavy rain.
    There may be other reasons for CYA loss, but these are two most prominent reasons

    Dichlor uses CYA as a stabilizer, so adding Dichlor will also raise the CYA. Prolonged usage of Dichlor, Trichlor or any other "chlor" shock will eventually lead to higher than acceptable CYA levels and render the required minimum FC unsustainable and you end up with algae.

    Many of the pool industry folks do not understand the chemistry of the FC and CYA and will flat out tell you, its normal to expect a couple of algae blooms a season.

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    Re: SWCG and CYA

    but a SWCG pool and a Dichlor pool put side by side will show a marked decreased of CYA in the SWCG pool.
    Why would you think that? That is new to me and I don't think anyone on the forum has reported that observation. Can you help us understand where that came from?
    Dave S.
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    Re: SWCG and CYA

    I am just surmising and questioning why this happens. Some of you on here even related that in when you winterize your pools, the CYA stays constant from closing to opening.

    Something is happening in SWCG pools, I am just curious. I have mine at 70 ppm now, but I guarantee you in 2 months I will be needing to add more.

    I should add, this loss isn't from spashout or replenishment over the summer. Love to hear from other people with SWCG or perhaps Chemgeek.

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    Re: SWCG and CYA

    If you are properly chlorinating your pool and you need to raise CYA in two months you are either backwashing a lot or you have a leak or there has been a tremendous amount of rain causing the pool to overflow (or be drained back to normal level).
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: SWCG and CYA

    Jason, I am not losing that much water, there is no leaking whatsoever, this descrease of the summer months has happened since I put my SWCG in 8 years ago. My Chlorine readings are constantly at 4 to 6 ppm. Do you also show some CC's when doing DPD testing?

    I know a level around 70 ppm to reduce 10 ppm would require a lot of replacement and rain, I would recognise this I hope lol

    Once you get your levels up to manufacturers levels, do you lose a significant amount over the year?

    Love to see some readings over a period of time.

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    Re: SWCG and CYA

    I raise CYA to 80 in the spring and it is between 60 and 70 the next fall five or six months later. The only exception has been years when we get a *lot* of rain, and thus overflow. The behavior can be a little different if the water is very warm.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: SWCG and CYA

    Thanks Jason, much appreciated, I shall be monitoring my CYA levels and noting it.

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    Re: SWCG and CYA

    I was surprised at how much a 6+" rain one afternoon diluted my CYA. Pool was very close to overflowing onto the deck. If I recollect correctly, my CYA dropped by 15 from 65 to 40.
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    Re: SWCG and CYA

    Ok, to go off base a bit, if one used just liquid chlorine, and mainly at night, would one be able to run a pool without any stabilizer at all? I believe indoor pools are now recommended to use 10-30ppm to act as a buffer?

    Reason for asking, I see many areas are now against Salt Water Pools and backwashing going into the water table. I fear my area could soon be going that way as well. I know that liquid chlorine/bleach also adds some salt with every dosing, but I believe minimally?

    I really love the idea of a pump and container of liquid chlorine/bleach but am afraid of what appears to happen in every puck pool I have been in, their CC's are thru the roof and the smell of Chloramines is rather annoying.

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    Re: SWCG and CYA

    It is possible to run a pool without any CYA, but you use *way* more chlorine and the chlorine is much harsher with higher CC levels.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: SWCG and CYA

    Chlorine does slowly oxidize CYA, but it's usually around 2-3 ppm CYA per month unless the chlorine level and pH are both fairly high. So an extended SLAM might see some CYA loss though usually one doesn't SLAM long enough to notice.
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