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Thread: Can't keep FC level above 0.1

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    Can't keep FC level above 0.1

    This is my first post. I am glad that I found this site a few weeks ago and have it bookmarked it. I wished that I had found this site when we purchased our pool in 2013.

    The pool water is crystal clear and has been since it was cleaned after removing the cover about four weeks ago. This is the first year that I can't get the FC to increase. Weekly, I have been shocking the pool with 2 pounds of 73% Cal hypo and adding the algaecide.
    Three weeks ago, I began taking the water for testing at the pool store. Each week the results were:
    Week 1) FC 0.09 CYA 157
    Week 2) FC 0.1 CYA 132
    Week 3) FC 0.1 CYA 40

    I thought that there was no way that the CYA level reduced that much in one week so I had it tested at a second pool store. FC 0.1 CYA 139
    Yesterday, I received the TF-100 kit (no more pool store tests) and put it to use. That test had the CYA at 100 and FC at near 0.

    Should I drain the pool water to reduce the CYA? If so, should I attempt to get it at 50? I can only go to the bottom of the skimmer each time since I don't have a bottom drain installed.
    Chlorine 20x40 IG vinyl pool, 28400 gallons, sand filter

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    Mod Squad jblizzle's Avatar
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    Re: Can't keep FC level above 0.1

    Welcome to TFP!!!

    If you want to take control, you need to stop having your water tested at the pool stores (you data even shows why) and in vest in one of the Recommended Test Kits.
    I should read the whole post before typing

    Post up a full set of test results. Yes, you need to replace water to lower the CYA level, and then you will need to follow the ShockLevelAndMAINTAIN Process to take care of whatever is consuming your FC.

    You can either rent or buy a sump pump which will be WAY faster and less water than trying to only replace 3" of water at a time. Or can you just setup a siphon with a hose?

    We also do not "shock" with cal-hypo and do not recommend the use of expensive algaecides.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    Texas Splash's Avatar
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    Re: Can't keep FC level above 0.1

    A little draining ahead of you, but not too bad if the CYA is indeed close to 100 and not higher. Welcome to TFP!
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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    Re: Can't keep FC level above 0.1

    Week 1) FC .09
    TC 0.37
    pH 7.8
    CH 171
    TA 87
    CYA 157

    Week 2) FC 0.1
    TC 0.2
    pH 7.6
    CH 161
    TA 96
    CYA 132

    Week 3) FC 0.1
    TC 0.4
    pH 7.6
    CH 181
    TA 90
    CYA 40

    Using the TF-100 kit
    TC 0.5
    pH 7.5
    CH 175
    CYA 100
    Chlorine 20x40 IG vinyl pool, 28400 gallons, sand filter

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    Mod Squad jblizzle's Avatar
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    Re: Can't keep FC level above 0.1

    What is the FC and CC? Did you do the FAS-DPD chlorine test? TA?

    I am ignoring everything before the TF100.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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    Texas Splash's Avatar
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    Re: Can't keep FC level above 0.1

    Swimguy, what a difference in numbers with your own test kit huh? Looks like you still need to do a bit more water exchange though. Next time you post your results, please post all of them as follows:
    FC
    CC
    CYA
    pH
    TA
    CH (not normally necessary for a vinyl pool, but okay to post)

    It will help us all. Glad you got that kit!
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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    PAGirl's Avatar
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    Re: Can't keep FC level above 0.1

    Your CYA could be above 100. You can follow the instructions for diluting (step 9 under testing CYA) to find out if it is.
    Pool School - CYA
    26' X 52" Intex Ultra Frame. Intex Sand Filter
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    You can lead a horse to (clear) water, but you can't force him to swim in it!

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    cowboycasey's Avatar
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    Re: Can't keep FC level above 0.1

    Quote Originally Posted by PAGirl View Post
    Your CYA could be above 100. You can follow the instructions for diluting (step 9 under testing CYA) to find out if it is.
    Pool School - CYA
    +1, I agree, your CYA may be closer to 200.. post up you new numbers and we can get you going
    Pool: Intex 16x32 15000 gal, 2 speed 340042, Pentair CC320 Filter, CircuPool SJ45 Salt System, Intermatic PE653RC; Hot Tub: 650 Gal SWG Megachlor
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    JoeSelf's Avatar
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    Re: Can't keep FC level above 0.1

    You can drain past the skimmer using a vacuum hose and vacuum head at the bottom of the pool. I had to do a 50% drain and this is how I did it.
    13700 gal, 32'x16'x54" AG oval, vinyl, Echo Canyon II, 8500 series, Narrow Yard, Safety Fence & Stair, Sta-Rite Crystal Flow T-210WF, 44 GPM, Hayward SP1580TL 1HP Pump, Aqua Luminator, Festiva wedding cake steps, March 2006, TFT-100, Speed-Stir, Sample Sizer. Avatar Credit: TJ Townsend

  10. Back To Top    #10

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    Re: Can't keep FC level above 0.1

    Thanks for the replies. Non stop rain has prevented further testing. I'll post them over the weekend.
    Chlorine 20x40 IG vinyl pool, 28400 gallons, sand filter

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    Re: Can't keep FC level above 0.1

    Yesterday, I drained the water to the bottom of the skimmer. I added three inches of water . Afterwards, it rained 1.5 inches. Just before dusk, I added 2.5 pounds of cal hypo (getting rid of what's left before switching to regular chlorine) About 30 minutes ago, I used the TF 100 kit and got the following results.

    TC 4.0
    CC 1.0
    FC 3.0
    TA 160
    CYA 100 (I used the step 9 method)
    pH 7.5

    The water remains very clear.
    Thank you for your help
    Chlorine 20x40 IG vinyl pool, 28400 gallons, sand filter

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    Texas Splash's Avatar
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    Re: Can't keep FC level above 0.1

    Those are good improvements. Now just remember to refer to the Chlorine/CYA Chart table. A CYA at 100 requires a "minimum" FC of 7, target FC of 12. And that's IF the CYA is only 100. Yours may still be higher, so you may want to increase that FC and/or continue some more partial drains while there are rains in the forecast. If you have any more questions, give us a shout.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
    If you enjoyed your TFP experience, please consider donating to Support TFP!

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