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Thread: Need Help Determining Numbers For Shock

  1. Back To Top    #1

    Join Date
    Jul 2009
    Location
    Richmond, Michigan
    Posts
    12

    Need Help Determining Numbers For Shock

    Last fall, a big storm pulled part of the cover off our pool and tons of leaves got into the water. We fixed the cover as soon as we noticed it but didn't remove the leaves from the water (HUGE mistake!!). Last weekend, when we opened the pool, the water was, of course, brown and murky. We have scooped all of the leaves out of the pool, but now are left with nasty brown water. We debated whether to treat the water or drain the pool, but have decided to try to treat it. I'm not sure if this was a good call or not. If we drain it, we could be swimming in it by this time next week. Not sure how long it will take to get clean water by treating this mess. We have been running the filter constantly and need to start adding chemicals.

    The readings today look like this:

    TH - 20
    FC - O
    PH - 7.5
    TA - 240
    CYA - 0

    We would like to shock it today, but I'm unclear on what FC level I should be trying to achieve. From what I read about shocking, you should never raise the FC level above 5 if your CYA is 0. Can anyone help me?
    15 x 24 AG Vinyl, 10,500 Gallons, 1 hp StaRite Pump, Cartridge Filter

  2. Back To Top    #2

    Join Date
    Feb 2008
    Location
    Flower Mound, TX
    Posts
    5,062

    Re: Need Help Determining Numbers For Shock

    Best to go ahead and add enough CYA in there to raise your CYA to 30, then shock with an FC of 12. That helps the FC persist in the water a little bit better. So just put the CYA in a sock, enough for 30 ppm, then commence shocking by raising the FC to 12 and holding it there as best you can. You may have to recheck the FC hourly in the beginning, especially since it is sunny.

    You can also go ahead and just add the CYA now and then start you shocking after the sun has set. Up to you.

    Have you gotten yourself a good test kit yet? You'll need it. Here is the Test Kit Comparison page to help you decide. The TF-100 is the best value among them.
    10K gallon IG gunite with waterfall; Pentair CC320P filter; WhisperFlo 2 HP pump
    TF Test Kits - Pool Math - Pool School
    "It depends."- JohnT

  3. Back To Top    #3

    Join Date
    Jul 2009
    Location
    Richmond, Michigan
    Posts
    12

    Re: Need Help Determining Numbers For Shock

    Thanks, that makes sense. I was worried about getting the FC level too high and causing damage.

    A friend of ours told us he cleared a swampy pool by using the packets labeled "shock treatment". I've never used it, so I'm not sure what it is. Does anyone have any input on this product? Is it used in addition to CYA and bleach?
    15 x 24 AG Vinyl, 10,500 Gallons, 1 hp StaRite Pump, Cartridge Filter

  4. Back To Top    #4

    Join Date
    Feb 2008
    Location
    Flower Mound, TX
    Posts
    5,062

    Re: Need Help Determining Numbers For Shock

    Some products such as dichlor will add both CYA and chlorine. If the product is dichlor (read the ingredients) then you can use it. Just be sure not to add any more than what is required to get your CYA up to 30, and then switch to non-stabilized chlorine sources (bleach) to complete the job.

    Other stuff that is sold as "shock" is often calcium hypochlorite. Cal-hypo adds no CYA but it does add calcium. Not such a big deal for you since you have a vinyl liner, but it would be more expensive than just adding bleach.
    10K gallon IG gunite with waterfall; Pentair CC320P filter; WhisperFlo 2 HP pump
    TF Test Kits - Pool Math - Pool School
    "It depends."- JohnT

  5. Back To Top    #5

    Join Date
    Jul 2009
    Location
    Richmond, Michigan
    Posts
    12

    Re: Need Help Determining Numbers For Shock

    Excellent info! Thanks so much! I think it would be best to stick with CYA and bleach and just skip the shock packets.
    15 x 24 AG Vinyl, 10,500 Gallons, 1 hp StaRite Pump, Cartridge Filter

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