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Thread: SWg why such a high CYA level

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    fofa's Avatar
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    SWg why such a high CYA level

    I used to try to keep my CYA in the 20-40 range when I was running a chlorinator. Seemed to work pretty good over all. Now i have a SWG and the range is 80-100. I keep mine around 80, but still seems top require a high CL reading to keep algae at bay. Is there some intrinsic reason that a SWG requires a much higher CYA level? Since my MFG recommends this level, I have tried it, but am not that happy with it. But I don't want to cause early cell wear or anything.
    30,000 Gallons, Hayward C5030 cartridge filter, IG, Plaster, SWG

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    mas985's Avatar
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    Re: SWg why such a high CYA level

    Many on the forum have experienced a lower required SWG setting with higher CYA even though the CL levels must be kept at a higher level. Conventional wisdom is that the CL level should be at least 5% of the CYA so for a CYA level of 80 ppm, CL levels must be kept at 4 ppm. I found for my pool, that at a CYA 45 (CL 2.25ppm) I required a higher SWG setting than for a CYA of 80 ppm (CL 4 ppm). Your results may vary but it could be that your residual CL level is not high enough for the CYA of 80 ppm.
    Mark
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    JasonLion's Avatar
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    Re: SWg why such a high CYA level

    At higher CYA levels you don't need to add as much chlorine to the pool, so you can run the SWG at a lower percentage and it will last longer and cause less PH drift. At the same time, at higher CYA levels you need the FC level to be higher than at lower CYA levels. This can be kind of counter intuitive, at higher CYA levels you need higher FC levels but it still takes less chlorine added to the pool to get to that higher FC level.

    Around here we recommend that CYA be around 70 to 80 with a SWG, regardless of brand. Higher CYA levels can be problematic if something goes wrong and you end up having to fight algae.
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    Re: SWg why such a high CYA level

    There is actually a bit more to it than the above explanations. This post helps explain why a higher CYA level is used with a SWG.
    viewtopic.php?f=21&t=3663
    With a CYA of 80 ppm you should not have any problems if you have at least an 8 hour pump run time and adjust your cell output to maintain about 4 ppm FC. If you are trying to do it with a shorter pump run time you might have problems.

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    Re: SWg why such a high CYA level

    Last summer my pool was new. Based on numerous test numbers from the pool store I thought my cya was 60-80. I ran my swg at 80-100% in order to get 3-4 ppm. After finding this site and getting educated I bought a TFTest kit and found my cya to be 30-40. I raised it to 80 this spring and in the heat of the summer I ran my swg at 20% (2.8 hrs/day of "on" time) to hold a FC of 5. Now that it has started to cool off my FC is 7 @ 2.4 hrs of "on" time. Not only is cell life being conserved, my ph rise is less thus less ma is being used. I'm a believer. Thanks TFP!

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