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Thread: Understanding CYA to FC-yes, basic Newbie question

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    Understanding CYA to FC-yes, basic Newbie question

    Yes, you can laugh if you want.

    Looking at the Chlorine/CYA Chart. Opened my pool this morning. Adding in about 1/3 water back in pool (pool is 29,700 gal. so roughly 9,000 gal adding in).

    Pool looks crystal clear. No smells. Once I fill to jets and start pool up I will test with my TF-100 Kit.

    My initial question (so I’m understanding this) as an example if my CYA is say 50 my target Chlorine level should be 5.7? That seems really high. My test kit for the daily quick check (k-1000) only goes to 5.0ppm. Trying to get up to speed again... I always thought you want your chlorine at about 3-5 regardless of CYA?

    I use the BBB method. Last year my CYA on average was about 50. I maintained my Chlorine between 2-4ppm. According to this chart that was way to low.

    Confused. Help clarify please.

    Also regardless of my current pool condition (which is clear, looks and smells great) do I still need to “shock” for pool opening? I live in Wisconsin home of the snownomie!

    PS. my pool will be full by morning so I will startup pump by noon tomorrow.

    THANKS FOR ANY ADVICE...go ahead and laugh now
    • 29,700gal. (18x40, avg depth 5.5'), Cartridge Filter (Pentair Clean & Clear CCP420)
    • IG, Vinyl, 1 HP Pump (Pentair SuperFlo High Performance), Pentair Master Temp 250
    Blink
    brett@blinkvisuals.com

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    Richard320's Avatar
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    Re: Understanding CYA to FC-yes, basic Newbie question

    You understand the chart correctly. It's not a big deal - as long as the OTO test is at least as yellow as the top block, you're probably okay. Beyond about 8 it starts to look school bus yellow and then goes into shades of orange and brown. You should be testing it with the FAS-DPD test at least once a week anyway to check yourself. As an aside, you won't generally use more chlorine on a daily basis that you di at a lower level, only a little extra to get it to the higher level initially. I would say you had beginner's luck not getting an algae bloom last year, so don't push your luck.

    Whether or not you need to perform the shock process depends on the readings you get once the pool is full and has had an hour or so running to mix things. If the water is clear and the CC (the powder FAS-DPD test) is .5 or less, then, no. Just take it up to the target FC for your CYA.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Understanding CYA to FC-yes, basic Newbie question

    Thanks Richard! When I closed the pool it was in perfect balance thanks to BBB. I added an extra amount of liquid Chlorine and threw the tarp over it and called it good. I think using a tarp versus a pool cover screen I think helps a lot in opening a pool. It totally keeps out leaves and all debris and sun cannot get to it. Seems the people who go with those mesh covers with all the rain and **** that gets through just turns there pool into a stew...resulting in problems. I will post my tests tomorrow after she gets up to speed. Thanks again for the advice, this site is the best!!
    • 29,700gal. (18x40, avg depth 5.5'), Cartridge Filter (Pentair Clean & Clear CCP420)
    • IG, Vinyl, 1 HP Pump (Pentair SuperFlo High Performance), Pentair Master Temp 250
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    brett@blinkvisuals.com

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    Re: Understanding CYA to FC-yes, basic Newbie question

    Just got done with my initial test after letting jets run for the past 8-hours.

    FC-1.5
    CC- 0
    TC-1.5
    PH-7.3
    TA-130
    CYA-40
    Temp-56

    So according to CL/CYA Chart I should bring my Chlorine up to 4.6? Need to add 1gal & 2quarts of liquid Chlorine right?
    What should i do about my TA its a little high?
    Also my PH is a little low? Add Borax?

    I have the jets on full and the water is breaking the surface so continue to aerate, that will raise my PH and lower my TA right?

    Help anyone?
    • 29,700gal. (18x40, avg depth 5.5'), Cartridge Filter (Pentair Clean & Clear CCP420)
    • IG, Vinyl, 1 HP Pump (Pentair SuperFlo High Performance), Pentair Master Temp 250
    Blink
    brett@blinkvisuals.com

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    Richard320's Avatar
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    Re: Understanding CYA to FC-yes, basic Newbie question

    Quote Originally Posted by Blink
    Just got done with my initial test after letting jets run for the past 8-hours.

    FC-1.5
    CC- 0
    TC-1.5
    PH-7.3
    TA-130
    CYA-40
    Temp-56

    So according to CL/CYA Chart I should bring my Chlorine up to 4.6? Need to add 1gal & 2quarts of liquid Chlorine right?
    What should i do about my TA its a little high?
    Also my PH is a little low? Add Borax?

    I have the jets on full and the water is breaking the surface so continue to aerate, that will raise my PH and lower my TA right?

    Help anyone?
    You understand correctly!

    The pH is fine. It will rise with aeration. The TA will come down slowly as you adjust pH when it climbs up towards 7.8. No need to rush it, the water's too cold to get in anyway.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Mod Squad jblizzle's Avatar
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    Re: Understanding CYA to FC-yes, basic Newbie question

    What chart are you looking at to have decimal targets? Use this one: pool-school/chlorine_cya_chart_shock

    With a CYA of 40ppm, never let the FC get below 3ppm ... so likely need to target 5-6ppm so that it is not below 3ppm by the next day.

    pH is fine, it will rise due to the TA. If you want to lower the TA: pool-school/lowering%20total%20alkalinity
    Jason, TFP Moderator
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    Re: Understanding CYA to FC-yes, basic Newbie question

    Thanks Richard!! I will do accordingly.

    jblizzle the chart i used is on this site. Seems to be two charts. I will stick with 5-6ppm. That way I’m safe.

    Thanks everyone, now I need some 85-degree days!
    • 29,700gal. (18x40, avg depth 5.5'), Cartridge Filter (Pentair Clean & Clear CCP420)
    • IG, Vinyl, 1 HP Pump (Pentair SuperFlo High Performance), Pentair Master Temp 250
    Blink
    brett@blinkvisuals.com

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    Re: Understanding CYA to FC-yes, basic Newbie question

    He was looking at the Chlorine/CYA Chart by Chemgeek that is referenced in a footnote in the Pool School Chlorine/CYA Chart.

    It's the minimum FC that you don't want to go below so if you are adding chlorine once a day and you know you lose 2 ppm FC then you'd want to add chlorine to get to 2 ppm higher than the minimum.
    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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