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Thread: Could my CYA have dropped? Now 40... that okay? Recommended level?

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    bbrock's Avatar
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    Could my CYA have dropped? Now 40... that okay? Recommended level?

    Hi TFPers,
    Yesterday was full test day. In the on-season, I perform my full testing approx. 1x/mo. At 0745, here were my results:
    pH 7.6
    FC 5.5
    CC 0
    TA 60
    CH 1100 (yes, I know high, but that is not the topic of this thread. I am managing it and using Pool Math to keep h2o balanced)
    CYA 40
    water temp = 82

    I added 28 oz chlorine (I use 12.5%) and 37 oz MA (I use 14.5%). When my CYA was 50, on the days I added chlorine I would always add to the upper limit of the recommendation. So, I added 28 oz chlorine to bring up my FC to 7.

    I am curious how my CYA could have dropped to 40. For approx. a year since I have been managing my water and using the TF-100, it has been 50. I did a partial drain/fill last year around this time to bring it down to 50. FWIW, if it may have affected things, I recently began using a 8 mil solar cover. Is a CYA of 40 okay? I have read so many threads on here that have discussions about different CYA levels. It appears there is no clear cut answer. My pool generally gets sun for approx. 8 hr/day +/-.

    Is there a recommended level given my details?

    Tx for any help.
    19k gal IG plaster, built '70s, probably resurfaced in '80s-'90s; Blue Haven Hayward filter C4520BHMB (Filbur FC-1275 cartridges); Hayward MaxFlo sp2302 VSP 1.5hp; 6 solar panels 288. sq. ft. total (142"x47.5" ea.) on 1 story hm; Pentair Compool LX220 Solar Controller; FlowVis flow meter; Maytronics Dolphin S200; AG 300 gal AquaTerra spa; TF-100 & Speedstir; gone: Pentair Challenger 3/4 HP 1 speed; Polaris 280

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    Mod Squad jblizzle's Avatar
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    Re: Could my CYA have dropped? Now 40... that okay? Recommended level?

    Just wrote this in another thread:
    CYA is consumed at a very low rate. Plus losses to splashout and backwashing and rain overflow.
    And sometimes over the winter it get converted to ammonia and drops to zero, although usually in a neglected pool.
    If you get a lot of intense sun, then up around 50ppm is good, less sun, then lower toward 30ppm is fine.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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    bbrock's Avatar
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    Re: Could my CYA have dropped? Now 40... that okay? Recommended level?

    Tx Jason.

    Per the recommended levels page, it appears that 40 is right in the middle of the recommendation for plaster with bleach (http://www.troublefreepool.com/conte...mmended-levels). Yes, in the summer I get some intense sun for up to 8 h +/-, but again it is only 8 h. Not sure how to quantify "intense" from a temperature perspective or duration.
    19k gal IG plaster, built '70s, probably resurfaced in '80s-'90s; Blue Haven Hayward filter C4520BHMB (Filbur FC-1275 cartridges); Hayward MaxFlo sp2302 VSP 1.5hp; 6 solar panels 288. sq. ft. total (142"x47.5" ea.) on 1 story hm; Pentair Compool LX220 Solar Controller; FlowVis flow meter; Maytronics Dolphin S200; AG 300 gal AquaTerra spa; TF-100 & Speedstir; gone: Pentair Challenger 3/4 HP 1 speed; Polaris 280

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    Mod Squad jblizzle's Avatar
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    Re: Could my CYA have dropped? Now 40... that okay? Recommended level?

    If you are losing more FC every day than you like, then raise the CYA level up some. Normal to have to add 2-4ppm of FC every day.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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