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Thread: FC and CYA levels - what determines the range??

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    FC and CYA levels - what determines the range??

    Hard to ask a question in a topic and have it make sense sooo.....

    I've looked at the PS recommended levels and understand the relationship between FC and CYA but my confusion lies in the ranges listed for the recommended levels. FC is listed as from 3-7ppm with the corresponding CYA of 30-50, are the ranges a matter of personal preferences or specific to certain types or pools, or climate, etc, etc. Most of the posts I've read have a recommended CYA of 30 but I have seen other posts where people are running it at 40 which obviously pushes up you FC level.

    I've got a 24 ft Sharkline Matrix AGP coming and just want to make sure I've got everything running as perfectly as possible using BBB. So is there a "perfect" level that I should be aiming for???

    Thanks and I hope that made sense, lol
    24 Ft Sharkline Matrix , ~15,200 Gallons
    Pentair SD60 w/ 2 speed 1.5 HP Dynamo pump
    Taylor K-2006 --- BBB

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    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Tucson, AZ

    Re: FC and CYA levels - what determines the range??

    Kind of pool dependent.
    The CYA is protecting the FC from the sun.
    So if a pool is always in the sun, it would likely benefit from lower FC loss with a higher CYA.

    At CYA 30ppm the minimum FC is 2ppm, but they find they are loosing 4ppm per day ... so they have to dose to 6ppm to stay above the min
    At CYA 40 ppm the min FC is 3ppm, but they may actually only loose 3ppm per day ... again dose to 6ppm, but using less bleach
    At CYA 50 ppm the min FC is 4ppm, but maybe the loss is now only 2ppm per day ... dose up to 6ppm, but now using half the bleach as at 30ppm

    These loss numbers are completely made up and maybe exaggerate, but give the basic idea.

    The problems start to happen when you have the higher CYA and then something happens where you have to shock. The shock levels are much higher as the CYA increases.

    So it will take some dialing in for your pool. We say start at CYA 30ppm and see what your FC usage is, if acceptable good. If seems high, bump up the CYA. Much easier to add than remove.

    Review the pool-school/chlorine_cya_chart_shock
    Jason, TFP Moderator
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    Mod Squad woodyp's Avatar
    Join Date
    Apr 2010
    East Texas

    Re: FC and CYA levels - what determines the range??

    YES!..........There is a PERFECT level for your pool! You're just gonna have to wait for YOUR pool to tell you what that is. They are all different. 30 CYA is a great place to start rather than to over shoot. Losin' too much FC there daily?------take it to 40 and see. Or up to 50 in a hot weather/hot pool water full sun all day.
    16x32x52" Steel Cornelius Miramar AGP Vinyl liner 13,100 gal. Buried 2 ft.
    2 Speed Hayward Power-Flo Matrix 85 g.p.m. 22" 250lb. sand filter hard plumbed
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    Re: FC and CYA levels - what determines the range??

    Gotcha, that makes complete sense now. My AGP will be in direct sun pretty all day long so it looks like my CYA "may" need to be higher.

    Thanks woody and jblizzle
    24 Ft Sharkline Matrix , ~15,200 Gallons
    Pentair SD60 w/ 2 speed 1.5 HP Dynamo pump
    Taylor K-2006 --- BBB

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