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Thread: first time TF-100 user - quick fc drop 7 to 0.5?

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    first time TF-100 user - quick fc drop 7 to 0.5?

    hello all,

    just received my tf-100 kit and joined this excellent forum this week. here are my numbers from last night and this afternoon (3:00pm)...

    last night->today
    fc: 7 -> 0.5
    cc: 0.5 -> 0
    ph: 7.5 -> 7.5
    t/a: 120 -> 110
    ch: 170 -> 220
    cya: 60 -> 60

    pool is essentially in the shade by 3:00pm...extremely light bather load to this point....water is clear.

    seems like a very big drop in fc. anything of concern here? or should i just add chlorine/bleach tonight (as per chlorine/cya chart and pool calc)?

    appreciate the time for a newbie!

    danny
    20k gal, cartridge, IG, plaster

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    JasonLion's Avatar
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    Re: first time TF-100 user - quick fc drop 7 to 0.5?

    Welcome to TFP!

    Yes, that is a very large drop for CYA at 60, I would expect FC to be down to 4 or 5. On the other hand it could be a testing error of some kind. CH shouldn't have gone up like that unless you added calcium. You just got the test kit, so perhaps one or the other of the FC and CH tests were mistaken.

    I suggest doing a quick double check with the OTO chlorine test (in the Taylor K-1000 kit that comes inside the TF100). The OTO chlorine test is a good way to quickly check for FC being very low or not very low, though it isn't so good at giving you specific numbers for FC levels over 2.
    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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    Re: first time TF-100 user - quick fc drop 7 to 0.5?

    thanks for the welcome, jason. it's good to be here!

    i took your suggestion, and the oto test confirmed the extremely low chlorine reading. i guess it's possible i made some mistakes last night, although i did take my time and tried to be very careful. at any rate, what do you suggest based on today's readings?
    20k gal, cartridge, IG, plaster

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    JasonLion's Avatar
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    Re: first time TF-100 user - quick fc drop 7 to 0.5?

    As long as the water remains clear, the best thing to do is to raise FC back up to the high end of the normal range and do an overnight FC loss test. If the water is at all cloudy or murky you should go straight to shocking the pool.
    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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    Re: first time TF-100 user - quick fc drop 7 to 0.5?

    water is clear, so i'll try to raise FC to 7 as per chlorine/cya chart. since CH at 220 is on the low side (slightly below normal range)...and considering that i have a bunch of cal-hypo 68%, i'd like to use the cal-hypo (approx 1.5 lbs) to raise FC this time. from reading pool school i understand that cal-hypo can have negative effects over long-term, but i think i'm safe at this point based on current CH level. is my thinking ok here?
    20k gal, cartridge, IG, plaster

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    JasonLion's Avatar
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    Re: first time TF-100 user - quick fc drop 7 to 0.5?

    Yep. Cal-hypo is just fine for now. When CH gets higher you will want to stop using it.
    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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    Re: first time TF-100 user - quick fc drop 7 to 0.5?

    whenever i've used cal-hypo (granular/powder) in the past, i typically add it through the skimmer. packaging states skimmer or adding directly into the pool water. is there a specific recommendation re: methodology?
    20k gal, cartridge, IG, plaster

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    duraleigh's Avatar
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    Re: first time TF-100 user - quick fc drop 7 to 0.5?

    Use the skimmer but not in one big "glomp". Put it in slowly so it will not interfer with the pump and go right to the filter.

    YOu could also pre-dilute it in water if you choose although I have never done that.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: first time TF-100 user - quick fc drop 7 to 0.5?

    ok, sounds good. thanks dave.
    20k gal, cartridge, IG, plaster

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