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Thread: 0 fc 0 cya what happened

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    0 fc 0 cya what happened

    My pool is mostly shaded and was taking a while to warm up so I bought a solar cover (clear/opaque) everything was fine for 3 weeks before we were swimming (in the 72 degree water) and pool has actually been up and running for about 6 weeks. Running just like normal FC loss of about a gallon and a half of bleach a week and CYA at 40. Skip forward a bit and I put the solar cover on, first time I test after 3 days or so I notice and abnormal FC loss down to 1 ppm. I figure it must just be concentrating the UV and eating up FC. No problem I add some bleach and things seem normal. The pool heats up fast and is in the 82 degree range and seems perfect except some yellow algae has formed. vacuum to waste backflush the filter and all is fine. Now the cover has been on for 3 more days since last "normal readings" (my CH is a little low 150 but they were out at first and I have been forgetting to grab it). Today it is super cloudy and FC and CYA have dropped to zero. Added 4 bottles of bleach 3 hours ago and still zero FC.

    Do I just keep adding bleach to kill whatever this is? Will it even work with zero CYA? Is my CYA really zero?

    Also it has been 98 degrees here for the last three days and the pool is now 87

    Current:
    FC: 0
    CC: 0
    PH: 7.5 (maybe slightly oranger 7.6)
    TA: 125
    CH: 150
    22,000ish gallon concrete pool.
    Taylor K-2006
    Sand Filter
    Joplin, Mo

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    borjis's Avatar
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    Re: 0 fc 0 cya what happened

    Sounds like you might have mustard algae.

    How exactly are you testing your cya? (inside/outside...etc)
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
    (1.5 HP motor) Raypak PR266AEN (266k btu) gas heater. TF-100 Test Kit.
    Dolphin E10 Cleaning Robot.

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    Pool Tool's Avatar
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    Re: 0 fc 0 cya what happened

    Just a guess - but if this is correct, it sounds like a CYA to ammonia (bacterial) conversion happening. I have seen it, but always on a closed (winterized) pool. Very strange! If that is it, FC will eventually beat ammonia but it takes FC additions, wait 10 minutes and test FC, add back to slam target, wait 10 mins, re-test and repeat until FC holds. Again, I don't know that this is that. I hope somebody with actual knowledge will be around to help soon.
    16' x 32' (21100 gal), vinyl, 1.5 hp Hayward SuperPump,
    Tagelus TA60/60D Sand Filter, Raypak 399K Digital Heater, TF-100

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    Mod Squad zea3's Avatar
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    Re: 0 fc 0 cya what happened

    Dose your pool to slam level (10 for 0 CYA) and re-test after 10 minutes. If you lose more than 1/2 your FC in 10 minutes raise it back up to 10ppm and test again in 10 more minutes. Keep up the 10 minute test and dose cycle until the FC starts to hold above 6ppm. At that point you should be able to add enough CYA to reach 20ppm and slam as normal.
    TFP Moderator
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    Re: 0 fc 0 cya what happened

    Not sure I understand the question, I add 7ML in the vial of pool water and then up to the 14 line of 0013. Shake for 30 seconds and add to the small side of my test cylinder. This is done pool side

    - - - Updated - - -

    Okay. Just used up my last 7 gallons of bleach to accomplish nothing.... How much more should I buy? 8.25% 22k gallons
    22,000ish gallon concrete pool.
    Taylor K-2006
    Sand Filter
    Joplin, Mo

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    Pool Tool's Avatar
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    Re: 0 fc 0 cya what happened

    As long as your CYA testing has been consistent, something has changed. Mustard algae shouldn't affect your CYA level. Zea has elaborated the ammonia process better than I have, follow that and let us know. Good luck.

    UPDATE
    Hard to tell but a warning, ammonia can be FC intensive. I would get a few more than normal. Sorry for your trouble.
    16' x 32' (21100 gal), vinyl, 1.5 hp Hayward SuperPump,
    Tagelus TA60/60D Sand Filter, Raypak 399K Digital Heater, TF-100

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    borjis's Avatar
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    Re: 0 fc 0 cya what happened

    Quote Originally Posted by Dkoucky View Post
    Not sure I understand the question,
    with your back to full sun and your body shading the viewing tube at waist level?

    Just wondering as some folks have tested cya indoors next to a lamp which is highly inaccurate.

    But as mentioned is sounds possibly to be an ammonia issue.
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
    (1.5 HP motor) Raypak PR266AEN (266k btu) gas heater. TF-100 Test Kit.
    Dolphin E10 Cleaning Robot.

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    Re: 0 fc 0 cya what happened

    Thanks guys will try! Should I give up on this solar cover or is it just a coincidence?
    22,000ish gallon concrete pool.
    Taylor K-2006
    Sand Filter
    Joplin, Mo

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    Mod Squad zea3's Avatar
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    Re: 0 fc 0 cya what happened

    It may just be coincidence. If you can spread it out on a flat surface and scrub it with some bleach and water solution it should be ok to use. Keep in mind algae grows quicker in warm water, so it may have accellorated a problem that was already there.
    TFP Moderator
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    Pool Tool's Avatar
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    Re: 0 fc 0 cya what happened

    Coincidence or not, last year I seemed to always have issues with my cover on for long stretches. Now I take it off every day or two even for just a half hour to let it breathe and I haven't had any of the same issues. For what that's worth.

    16' x 32' (21100 gal), vinyl, 1.5 hp Hayward SuperPump,
    Tagelus TA60/60D Sand Filter, Raypak 399K Digital Heater, TF-100

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