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Thread: Bringing shock up without reaching the CC breakpoint

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    Bringing shock up without reaching the CC breakpoint

    Split off of this topic. JasonLion

    I'm going through the same thing. I shocked last night (though didn't measure...) and measured this morning (Taylor FAS-DPD) and had 2.0 FC and 6.5 CC. My CC was previously at 4.0. My question is: according to the taylor manual you need to bring FC up to 10x the CC to "kill it off". However 65ppm will take a ton of shock. Am I okay using the recommended CYA/Chlorine levels? My CYA is steady at 30. From what I've read bringing shock up without reaching the CC breakpoint (e.g. 10x FC) will increase CC. Just want to make sure I'm working towards a fixed problem instead of a worse one.
    IG Gunite 25,000 gallons STA-RITE S7M120 cartridge filter 100GPM

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    JasonLion's Avatar
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    Re: Bringing shock up without reaching the CC breakpoint

    Welcome to TFP!

    That entire breakpoint chlorination story is a myth. It doesn't work that way.

    Shocking the pool is a process, not something you simply add to the pool and you are done. You need to shock the pool properly, as described in Pool School, and the CC level will come down. Your CC level is quite high, so it may take several days. It is possible that CC will go up before it starts coming down. Don't worry about that. Maintain the correct FC level for your CYA level (FC around 12) and you will be fine.
    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: Bringing shock up without reaching the CC breakpoint

    Thanks for the advice. My other issue is that my pH is now pretty low, 7.0. I'm using Borax to raise it back up (targeting 7.4-7.6) slowly. Any bad interaction between borax and calcium hypochlorite or recommendations on how to split up applying the two? My thought is to apply borax in the mornings and then shock in the evening.
    IG Gunite 25,000 gallons STA-RITE S7M120 cartridge filter 100GPM

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    Re: Bringing shock up without reaching the CC breakpoint

    Simply calculate enough Borax to reach around 7.3 and put it in as a one time dose.

    Then start your shock process an hour later.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Bringing shock up without reaching the CC breakpoint

    Thanks for the advice. I raised the pH last night to around 7.3 and then shocked. This morning the FC had dropped down to around 2 but the CC was very low (1ish, still getting used to doing the drop tests...). My plan is to raise the pH a bit more tonight (glad I bought 20 pounds of Borax while I was at the store instead of just a couple of boxes) and then continue to follow the pool school shocking advice.

    One other question is whether using a solar cover makes a difference good or bad when dealing with high CC or low FC. Does the solar cover increase FC depletion? My water is pretty cool (65 F) so I'm trying to keep the cover on as much as I can.
    IG Gunite 25,000 gallons STA-RITE S7M120 cartridge filter 100GPM

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    Re: Bringing shock up without reaching the CC breakpoint

    This morning the FC had dropped down to around 2
    Then you did not finish shocking your pool. Reread how to shock your pool in Pool School and you will find it is a continual process of adding chlorine and testing. You should never let the FC get low when you are shocking. Your FC should be held constant at 12ppm or a little more.

    Disregard your pH and leave your solar cover off until the shock process is complete.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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