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Thread: Effects of SWG produced chlorine

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    porkandbeans's Avatar
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    Effects of SWG produced chlorine

    I'll be the first to admit that I'm no chemist.
    As I understand it, with a chlorine pool you add chlorine, and with a saltwater pool the SWG produces chlorine. So how is chemical chlorine different than SWG chlorine? How come with SWG chlorine your eyes don't redden and you don't need to rinse off swim wear?
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    Re: Effects of SWG produced chlorine

    Are your comments about red eyes and rinsing off from personal experience? If so, can you give more details about the non-SWG and SWG pools? Or was this something a salesperson told you or that you read somewhere?

    The chlorine produced in an SWG (when combining chemicals from both plates and the chlorine has dissolved into the water) is the same as if you add chlorinating liquid or bleach except the salt level doesn't increase when using an SWG (technical details in this post).

    Red eyes are more often caused by out-of-range pH or very high active chlorine levels such as found in commercial/public indoor pools that don't use CYA or high combined chlorine (CC) levels that are sometimes found in high bather-load commercial/public pools sometimes using too much CYA. There is also a difference in osmotic pressure as a function of salt level so an SWG pool that has a higher salt level will have less pressure on the eyes, though still has some effect because the salt level in tears is 9000 ppm while the salt level in SWG pools is closer to 3000 ppm (see this post referring to this paper). One can increase the salt level in a manually dosed pool for the same effect on osmotic pressure -- this effect has nothing to do with the SWG or chlorine from the SWG itself.

    As for rinsing off swimwear, this is needed almost as much in SWG pools as in manually dosed pools. Again, perhaps you are comparing against commercial/public pools some of which do not use any CYA so their active chlorine level is much higher. My wife has experienced this difference between an indoor commercial pool that she used each winter and where her swimsuits would only last one winter season and her skin was flakier and hair frizzier so rinsing was very important. In our own outdoor pool, there were no such problems and her swimsuits have lasted for about 7 years and the effects on skin and hair are a lot less noticeable. The difference is that the commercial pool has 1-2 ppm FC with no CYA while our pool had 3-6 ppm FC with 30-40 ppm CYA which is roughly a factor of 10-20 difference in active chlorine level. Basically, many commercial/public pools (those not using CYA, so mostly indoor pools) are over-chlorinated.

    The target FC/CYA ratio in SWG pools is a little lower than in non-SWG pools, but the difference is not that large and unlikely to be very noticeable in terms of physical effects. We have many pool owners here manually dosing their pools and barely notice that they are chlorinated.
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    porkandbeans's Avatar
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    Re: Effects of SWG produced chlorine

    Thanks for the detailed explanation. It seems likely that my chlorine pool experiences may have been with over chlorinated pools. Whether public pools, family, or friends, as a kid I would be in the water all day and expect the foggy chlorine eyes. As saltwater pools have become popular over the last 10+ years (just as a user, not ownership) perhaps I fell into the urban myth that saltwater pools don't have chlorine. Never felt any chlorine effects at all and never actively put effort into rinsing a swinsuit. But then again, as an adult I don't spend as many countless hours under water or even in water. Now, as a first time pool owner, I am learning about proper pool maintenance. I previously thought that saltwater pools didn't have chlorine.
    Guess I'm off to rinse swimsuits!
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    UnderWaterVanya's Avatar
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    Re: Effects of SWG produced chlorine

    My pool is bleach chlorinated and every now and then someone asks how I keep a "freshwater pool" clean without chlorine.

    Proper levels keep the pool so fresh and clean it is hard to understand until you experience it.

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