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Thread: CYA level dropped off the charts.

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    DLO's Avatar
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    CYA level dropped off the charts.

    I was maintaining a CYA of 50 last year. The pool level was dropped 18" for closing last fall and refilled to operating depth in late April. I assumed my CYA would be at least close to the ballpark but couldn't test since my TF100 kit was depleted of reagent. I ordered a new TF100 a few days ago, recieved it yesterday. I tested the CYA to find that it was so low as to appear to be zero. (Completely clear solution post adding 0013 and transferring to reading vial.) I added 4lbs to a sock in the skimmer yesterday afternoon. I checked this morning and the entire 4lbs had been disolved. I tested a few min ago, hoping to see at least a small increase in CYA. Not the case. It's still reading too low measure. The pool is reacting as if the CYA level is low, high chlorine consumption when the auto cover is opened. I have another 8 lbs ready to go in, but I figured I'd ask what you guys thought before I did so. My main concern is the apparent total lack of a chemical, who's level is supposedly difficult to to decrease outside a water change. Thanks all.
    "Beer is proof God loves us and wants us to be happy." -B. Franklin

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    frustratedpoolmom's Avatar
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    Re: CYA level dropped off the charts.

    It can take 5-7 days to comletely dissolve and register on the tests - even if it appears to dissolve out of the sock. Testing sooner will just use up your reagent.

    Use the "Effects of Adding Chemicals" section of the pool calc to determine how much the 4 lbs raised your CYA by- just assume that is your level. If you need to add more to reach your target, its fine to do so...(I didn't check your numbers...)
    Helpful links: Pool School; CYA/Chlorine Chart
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    DLO's Avatar
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    Re: CYA level dropped off the charts.

    another bit of data: I added enough bleach yeterday to raise the TC to 10ppm. The cover was open all day. I just checked and TC is back to zero.
    "Beer is proof God loves us and wants us to be happy." -B. Franklin

    In-ground, vinyl lined, 20'x40', 3-10' deep, solar heater, sand filter, 3/4hp pump, Dolphin Pro, Cover Star Auto Cover.

    A proud BBB convert.

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    Re: CYA level dropped off the charts.

    If your CYA level went down to zero over the winter, you need to shock the pool until you don't have any overnight FC loss. It doesn't happen every time, but when CYA vanishes, it has often broken down into ammonia, which you then need to remove by shocking the pool.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    DLO's Avatar
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    Re: CYA level dropped off the charts.

    I shocked to 12ppm a few min ago. I'll leave the cover closed today/tonight and test in the morning for loss. I'm doing several things at once here. My TA is 280, so I dropped my pH to 7.0 last evening. I'm aerating now and will check pH and TA tomorrow when I check for FC loss. Would you think it advisable to add another 4lbs of CYA (bringing the assumed level to 20ppm) while I'm multi tasking?
    "Beer is proof God loves us and wants us to be happy." -B. Franklin

    In-ground, vinyl lined, 20'x40', 3-10' deep, solar heater, sand filter, 3/4hp pump, Dolphin Pro, Cover Star Auto Cover.

    A proud BBB convert.

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    JasonLion's Avatar
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    Re: CYA level dropped off the charts.

    Adding CYA while you are doing other things is fine.

    Remember that the PH reading can be off if the FC level is above 10.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    DLO's Avatar
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    Re: CYA level dropped off the charts.

    Yeah, I took the pH reading last evening when the FC was around 5, so I trusted the 7.0 before I started to aerate.
    "Beer is proof God loves us and wants us to be happy." -B. Franklin

    In-ground, vinyl lined, 20'x40', 3-10' deep, solar heater, sand filter, 3/4hp pump, Dolphin Pro, Cover Star Auto Cover.

    A proud BBB convert.

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    Re: CYA level dropped off the charts.

    I had the same thing happen to me. Pool was filled 7/13/2008 with 23,270 gallons, I added 16 #'s of CYA to get to 80 ppm, which is what it last tested on 8/10/2009. I used bleach and ECG to maintain FC above 7, and closed 10/4/2009 with FC at 10.5.

    I used a "lock-in" cover that basically puts the water under another 20 mil vinyl liner and keeps most things out, so I only lowered the water level 7-8 inches. I needed to add about 3000 gallons to start this year off when I opened 5/25/2010. I took a sample to two pool store's to test because I didn't have reagent for CYA (my FAS-DPD FC=4.5, CC=0, ph=7.4) and got 15 (computer) and 30 (Leslie's plunger/dipstick done too quickly, IMHO). I had started the pump only a few hours before taking a sample, but before adding water, and the temperature was 66, so I expected lower numbers.

    I added 2#s of CYA (for the fresh 3000 gal.,) turned on the ECG and the next day my FC was 3.5, CC=0. I upped the ECG, and added bleach, but still just maintained 3.5 FC. So on 6/2, I took samples in again and got CYA 30 and 50, both more then the 10 ppm rise that I expected, but believable, so I added 2#'s more CYA and ordered reagent(should have done that first ) ECG is keeping up better now, I'm not adding bleach.

    I waited until today to use my fresh reagent re-fill (Thanks for the quick shipping, Dave!,) and with both the small view tube, and the large plunger/dipstick cylinder my CYA is 60. So I need to go get some more (4#'s) CYA to get to 80 so that I can cut back the ECG run time.

    So over winter I lost half of my 80 ppm CYA, and it wasn't from dumping 3000 gallons of water.
    I haven't had a hint of a CC reading since I filled the pool back on 7/13/2009, but I do have ~ 48 ppm borates.

    I should have tested before opening last year, but I was getting a liner replacement.

    Next year I'll make sure to have the proper testing supplies on hand to start the season, and some CYA, too, as I expect that I'll lose it over winter again.
    22 x 40 IG vinyl lined, 23,570 gal.
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