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Thread: SWG target FC levels

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    SWG target FC levels

    In the Chlorine/CYA Chart by Chemgeek here:

    viewtopic.php?t=2346

    It states as follows:

    "3. Most saltwater chlorine generator (SWG) pools appear to prevent algae at a minimum FC level of 4.5% of the CYA level as compared with the roughly 7.5% of the CYA level shown in the "Min FC" column for manually dosed pools."

    This equates to the level required to acheive the same FC level as a non-SWG at around 60%.

    Would it then be correct to assume that if the Yel/Mstrd Min FC level at a CyA of 70 is 10.5 in a non-SWG pool the level required in a SWG pool should be .60 x 10.5 = 6.4 FC? If one is only trying to achieve target FC then .60 x 6 = 4.8?

    And assume that if the Yel/Mstrd Min FC level at a CyA of 80 is .60 x 12.0 = 7.2 FC? If one is only trying to achieve target FC then .60 x 9.1 = 5.5?

    In a SWG pool that has 30 CyA it would be for the Yel/Mstrd Min FC level .60 x 4.6 = 2.8? and target FC .60 x 3.5 = 2.2?

    Or is this incorrect. Just trying to understand.

    Aloha.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

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    JasonLion's Avatar
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    Re: SWG target FC levels

    The lower target FC levels for use with a SWG were discovered empirically. We don't know exactly why they work nor do we have enough experience with them to say anything about what happens with mustard algae or when the CYA level is significantly below 60.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: SWG target FC levels

    Thank you for the reply.

    So as I understand it from your answer it would be trial and error to acheive the correct FC for a given condition and CYA when using a SWG.

    Although practical experience of high CYA 60-80 in a SWG pool seem to work for some at 4-6 FC, without issues.

    It would be great if there could be a database where persons could post their experiences of SWG Unit type, CyA, FC levels, algae experience, ORP (if any), or unit power level, and poolsize; this might lead to a better understanding of what works and does not given varying conditions.

    Aloha.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

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    JasonLion's Avatar
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    Re: SWG target FC levels

    Nearly everyone uses their SWG with CYA between 60 and 80 and they can follow the suggested levels in this chart. Those levels are reliable and apply to the vast majority of pools with a SWG. Trial and error is only required if you are operating outside of the normal limits, which we do not recommend.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: SWG target FC levels

    Quote Originally Posted by smallpooldad
    Thank you for the reply.

    So as I understand it from your answer it would be trial and error to acheive the correct FC for a given condition and CYA when using a SWG.

    Although practical experience of high CYA 60-80 in a SWG pool seem to work for some at 4-6 FC, without issues.

    It would be great if there could be a database where persons could post their experiences of SWG Unit type, CyA, FC levels, algae experience, ORP (if any), or unit power level, and poolsize; this might lead to a better understanding of what works and does not given varying conditions.

    Aloha.
    would be hard as these are not the only parameters affecting algae growth
    reason why it can operate at lower level is because it's constantly producing chlorine and constantly "shocking" all the water passing through it

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    Re: SWG target FC levels

    Strannik and JasonLion,

    Thank you both for your replies.

    Hopefully the ORP set at 690, will maintain an algae free enviroment if not we will have to switch to a % production method.

    Although going to the % method would mean having to adjust it upwards if the pool were left uncovered for any great length of time, such as a Sunday.

    Just have to wait and see.

    Aloha
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

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