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Thread: cya levels

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    Join Date
    Apr 2013
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    cya levels

    What is the purpose of cya in pool water?
    2500 gal. concrete, indoor, 3hp Pentair vs, 50 sq ft cartridge

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    Re: cya levels

    CYA is a chemical that acts as a stabiliser in swimming pools and helps to protect chlorine from breakdown due to ultraviolet light from the sun's rays.
    Sydney, AU | IG concrete / glass bead | ~8,000 Gal Kidney Shape | speck 90/230 w/Auto Clear SWG & Davies Sand filter|speck supersport swim jet | Attached Raised Spa | Pool just resurfaced |the pool cleaner | solar heated

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    Re: cya levels

    Thank you , so if my spa is indoors is there a need to have any?
    2500 gal. concrete, indoor, 3hp Pentair vs, 50 sq ft cartridge

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    JasonLion's Avatar
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    May 2007
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    Re: cya levels

    CYA does several things, slowing breakdown from sunlight is the main one, but there is another issue with spas.

    It is good to have low levels of CYA (around 20 ppm) in a spa to help buffer the required chlorine levels. Fairly large amounts of chlorine are required in a spa because there is a relatively high ratio of sweat to water. CYA slows down the action of chlorine, steering it away form producing some of the slightly harmful breakdown products, and more towards the safer breakdown products. It also increases swimsuit lifetime (if you wear swimsuits).
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: cya levels

    The chlorine will also outgas more slowly and degrade hot tub covers more slowly. Basically, CYA moderates chlorine's strength which would otherwise be too strong.
    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
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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