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Thread: high FC won't drop, high CC going on 3 weeks

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    high FC won't drop, high CC going on 3 weeks

    Hi all,

    I've had my pool for about three years and have had no issues at opening until this year...

    After I opened the pool and did the initial shock, I noticed that my FC levels were off the chart high on test strips but my water still smelled like chloramines. I shocked with non-chlorine shock and have seen no improvement after about 3 weeks. Pool water is crystal clear but had the beginnings of a brown algae bloom two days ago (Shocked again and vacuumed). After looking for solutions online, I saw the light and had a Taylor K-2006 FAS-DPD kit expedited to the house. The results (with the K-2006) are as follows:
    FC: 22 ppm
    CC: .5 ppm
    PH: 7.7
    Alk: 140 ppm
    Hardness: 230 ppm
    CYA: >100 full strength test; 140 ppm using 1/2 pool water/ 1/2 bottled

    water was 72 degrees.

    I brought a sample to the local pool store to double check (I needed a bag of DE anyway) and this is what they found:
    FC: OVER 17.23 ppm
    TC: OVER 17.99 ppm
    CC: .76 ppm
    pH: 7.9
    Alk: 105 ppm
    Hardness: 184 ppm
    CYA: 106 ppm

    I am wondering why my combined chlorine is so high with such a high amount of free chlorine. I am guessing that the FC is being impeded by the high CYA (also not burning off due to excess stabilizer?). At the moment, I'm doing a partial drain/fill to try and ease the CYA levels down. Am I on the right track here?

    As for the high FC/ CC, Should I try "breakpoint" chlorination even though the FC is high? I'm not sure I believe the whole "Chlorine lock/breakpoint" theory, and I don't want to add more chlorine if it isn't going to do anything. I'm at a loss at the moment, any help would be greatly appreciated...

    Side note: I haven't added CYA by itself since the first year; I'm assuming it just built up from using the stabilized tri-chlor.
    16 x 32 IG Vinyl 23000 gallons, Hayward DE 2420 filter
    Taylor K-2006 test kit
    3" stabilized Tri-chlor tabs in Hayward off-line chlorinator

  2. Back To Top    #2
    Mod Squad jblizzle's Avatar
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    Re: high FC won't drop, high CC going on 3 weeks

    Welcome to TFP!!!

    Forget about breakpoint non-sense. Your problem is that your FC is not high enough for you CYA as shown in the FC/CYA Chart. Your CYA is way too high and the first think you need to do is replace water to lower the CYA into the recommended 30-50ppm range. Then you need to follow the SLAM Process until you pass all 3 criteria to stop. And then you have to STOP using 3" tablets which are the cause of your problems.

    Stick with liquid chlorine for the SLAM and for maintenance.
    Jason, TFP Moderator
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    Mod Squad woodyp's Avatar
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    Re: high FC won't drop, high CC going on 3 weeks

    "Chlorine lock/breakpoint"......<<<<<<does not exist.
    16x32x52" Steel Cornelius Miramar AGP Vinyl liner 13,100 gal. Buried 2 ft.
    2 Speed Hayward Power-Flo Matrix 85 g.p.m. 22" 250lb. sand filter hard plumbed
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    Re: high FC won't drop, high CC going on 3 weeks

    I almost got "pool stored" (they told me to add more chlorine to break the "lock") but it just didn't make sense. They only reason I'm doubting myself is that even the K2006 manual mentions chlorine breakpoint and the pool still has high CC levels even with the high FC.

    I saw the CYA/FC chart and to me it looks like I should have a 7-12ppm FC residual at 100+ CYA with a shock level of 29ppm. Am I reading it wrong? My 22 ppm FC is still way high, even for that much CYA, no?

  5. Back To Top    #5
    Mod Squad jblizzle's Avatar
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    Re: high FC won't drop, high CC going on 3 weeks

    The shock level is 40+ppm with a cya that high. And 7+ is the minimum to avoid algae in the first place. In fact, since your CYA is 140, then you SLAM level is up around 55ppm.

    Replace water, lower CYA, then SLAM.
    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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