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Thread: CYA to FC Correlation

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    CYA to FC Correlation

    Currently my CYA is 50 and I've been pouring about 64oz of 12.5% bleach in daily to keep FC at 6 (14,500 gallon concrete pool). It seems a lot to me but maybe I'm just not used think liquid chlorine stuff as I just switched off pucks a couple weeks ago. All my other chemistry numbers are in check and water is crystal clear. When I have been checking every morning I am getting FC reading of only 1 which means I am losing 5ppm every day. That seem plausible? I would like to only be adding every other day as every day is kinda of a PIA, the pucks did have that going for them. Also with high CYA will the FC still show up on test even though it's not being used because of so much stabilizer of does the high CYA cancel out those FC readings?

    Thanks for your help

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    pabeader's Avatar
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    Re: CYA to FC Correlation

    Does the pool get sun most of the day? Have you tried doing an OCLT?
    Bob - INTEX 12x24 owner (not setup yet), 'New to me' Kreepy Krauly Sand Shark, Test kit: TF-100 w/Speed Stir

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    Mod Squad Jimrahbe's Avatar
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    Re: CYA to FC Correlation

    J,

    We usually say that pool uses 2 to 4 ppm of chlorine per day. Your 64 oz of 12.5% chlorine adds 4.3 ppm to your pool, so you are on the high end..

    As Bob suggests, I'd do an OCLT just to be sure it is the sun and not something in the water eating your chlorine..

    What you are finding out is exactly why a lot to TFPers are using a Stenner pump system or Saltwater Chlorine Generators...

    Thanks for posting,

    Jim R.
    Finished in 2015 - 17K Gal, IG, 20' x 25' Almost Rectangular Pool, Pebble finish, three rockport water falls. Pentair Equipment: EasyTouch 4, IC40 SWG, 3 HP VS Pump, CCP520 Cartridge Filter.
    TF100 with SpeedStir and SampleSizer, ColorQ Pro 7, Dolphin Premier Robot Cleaner, added Screen Logic 2, added small 3 person Caldera Spa.

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    Re: CYA to FC Correlation

    Thanks I will try the OCLT this evening, and yes I've been looking at the Steener pumps and automating this process. If I had algae or something else in the pool wouldn't I see it? The water is crystal clear and no complaints minus the excessive chlorine I appear to be using

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    Mod Squad jblizzle's Avatar
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    Re: CYA to FC Correlation

    It is possible to have algae that you can't see yet.
    Jason, TFP Moderator
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    Re: CYA to FC Correlation

    It does get a fair amount of sun throughout the hottest part of the day, and I'm in Austin too so it's hot

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    Richard320's Avatar
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    Re: CYA to FC Correlation

    Besides running an OCLT, here's a few other things to consider
    1) Testing error on the CYA. If you didn't have bright light, the dot will disappear too soon and give you a falsely high reading. I can see a distinct difference in results if I hold the view tube at just the top with thumb and forefinger or if I hold it more naturally with all my fingers touching.
    2) The pool is bigger than you think. When you dose with acid or bleach, do you see the results you're expecting or come up short?
    3) The bleach is old and not full strength anymore. If you get it at a pool store, there's probably a quick turnover. If it came from Lowes or Home Depot, it could have sat out in the garden center over the winter. Check the date code on the box. https://www.google.com/url?sa=t&rct=...M3b8XH92eqK-5Q
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Re: CYA to FC Correlation

    Must of had something in the pool that I couldn't see even though water was crystal clear. I went ahead and slammed it. Took FC up to 20, and after it settled back down to norm I appear to be doing a daily burn of 3ppm. So dropping from 6 to 3 FC per day and dropped my liquid usage from 64oz a day to 44oz. Think I'm good to go now.

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