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Thread: CH and CYA over time

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    CH and CYA over time

    I understand how FC and pH change over time based on sun, usage, etc... but, assuming normal evaporation and refilling and no draining of water, how are CH and CYA affected by evaporation? Are they both not affected by evaporation and essentially stay the same over the course of a summer, unless a large amount of water is pumped out? Or do they slowly decrease over time with standard evaporation and refill with water that essentially has zero CYA and CH?
    32K gal, gunite, French Gray DB, IntelliFlo VF, IntelliFlo, WhisperFlo, Quad DE 100 filter, IntelliTouch, IC-60 SWG, IntelliChem, Dolphin M5

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    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    SouthWest Alabama

    Re: CH and CYA over time

    They're not affected at all by evaporation and refilling. CYA is very very slowly oxidized by chlorine so it would slowly go down over the year.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: CH and CYA over time

    This is because evaporation on only evaporates water since CYA and calcium are not volatile. CYA is not in fill water, but CH often is so with evaporation and refill the CH will rise from adding it via the fill water. Water dilution from splash-out, carry-out, backwashing, rain overflow, etc. will lower the CYA and CH levels.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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