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Thread: Do I need to shock

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    Join Date
    Aug 2009
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    Pearland, TX
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    Do I need to shock

    We had rain this weekend and my pool is cloudy, blue but cloudy. Thursday I was in the pool which stirred up some sediment (I think dead algea) on the bottom of the pool. I also adjusted my return jet to point just under the water surface (previously it had been pointed further up and stired the surface of the water quite a bit).

    Here are the water test numbers

    FC = 17
    CC < .5
    Ph = 8.0
    TA = 220
    CH = 220
    CYA = 140

    I know that the CYA level is really high (but is better than the 220 it was about 2 weeks ago). I need to lower the Ph with, I think, will also lower the TA.

    Question: Do I need to shock to get the water to clear up? The FC is holding and the CC is low.
    Frank Jurgens
    21' AG, 11000 Gal Vinyl Liner
    Sand Filter

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    Re: Do I need to shock

    Well, checking the CYA chart it appears that since at CYA 30 shock level is 12 and at CYA 60 it is 24, then apparently we can just double the values for CYA 70 to get a shock level for CYA 140 of 56. Wow.

    So, you definately need to increase chlorine levels and is there a way to clear out the sediment/dead algae? Can you vac to waste?
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

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    Re: Do I need to shock

    Your pool will forever give you problems with algae until you make the comittment to lower your CYA.

    You don't say how you chlorinate so I assume you don't have an SWG. Your CYA needs to be 60 at the most and your pool will become far easier to manage.

    Take your pH down to 7.5 or so.

    EDIT: Dmanb2b makes a good point below that I missed......disregard your pH test until chlorine drops below 10ppm
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    dmanb2b's Avatar
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    Re: Do I need to shock

    to adds to daves comments, you really should address your CYA level...PH readings are know to be inaccurate (false high reading) when FC levels are 10ppm or above.
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

    Pool School, TFTestKits, Pool Calculator

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    Re: Do I need to shock

    I have already dumped about 1/3 of my water to get the CYA down to 140. I still need to do at least another 1/3 water change.

    I use bleach to add chlorine. I just started the BBB method about 2 week ago and I just got my test kit last week. The pool is looking better than it has in a long time.

    Another question: In general, do you need to shock after it rains, or do you only shock when there is a problem (like cloudy water to high CC)?
    Frank Jurgens
    21' AG, 11000 Gal Vinyl Liner
    Sand Filter

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    Re: Do I need to shock

    Quote Originally Posted by fdjurgens
    In general, do you need to shock after it rains, or do you only shock when there is a problem (like cloudy water to high CC)?
    In general, you only shock when there is a problem.

    In some cases you may choose to raise the FC level to head off a problem, like when you are expecting particularly heavy rains or maybe a big pool party.

    In our pool, I know that it can handle a 1 inch rain easily. Most of the time we get wind with the rains and I get a lot of pine needles in the pool so I take care to clean out the skimmers and Polaris promptly afterward. I am testing the pool at least every other day right now, so after the Polaris runs and the skimmers do their thing after a big rain I might test to see if I needed to add more chlorine, kinda just depends on how the pool looks. Dirt is worse than leaves I think and in a big storm I do get dirt washed in sometimes.

    Now if there was a Tropical Storm with forcasts of serious rain, 4 or 8 or 10 inches of rain I probably would bump the pool up to the top of the FC range or even a bit higher, maybe even drain down the pool a bit just so I don't have to do it in the middle of the storm. For me that is as much worrying about loss of power as anything else, better to have a bit extra in the pool if it may be offline for a few hours.

    But I haven't shocked my pool in a long time.
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

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    Re: Do I need to shock

    I still need to do at least another 1/3 water change.
    If you want to get down into a range you can manage handily, you need to do a little more than 1/2.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Do I need to shock

    I am going to get the CYA level down, I just don't have a full day to mess with my pool right now. That is what it will take to drain and fill the pool. I don't want to leave my pool only half full and risk the sun damaging the exposed liner.
    Frank Jurgens
    21' AG, 11000 Gal Vinyl Liner
    Sand Filter

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