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Thread: Theory vs Practice

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    Join Date
    Mar 2014

    Theory vs Practice

    My question is about how theory differs from practice.

    I have been monitoring a pool and all the parameters are balanced, except cyanuric acid.
    pH 7.2
    FAC 2.5-5
    CAC 0
    CH 300
    Alk 100
    CYA 100

    The thing is, the chart says that I am supposed to keep chlorine levels at a minimum of 7ppm, but the pool has levels below that and it is completely clear. I am talking of a SWG pool.

    Now parameters are the following:
    pH 7.0
    FAC 5
    CAC 0
    CH 150
    Alk 70
    CYA 90
    And the pool is completely clear! The water is out of balance and most of the parameters are too low.

    In addition, the pool guy backwashes filters every other day, without the pressure from the filter rising, and he claims that if he doesn't the pool gets turbid.

    So that leads to my question: How much does practice differ from theory?

    Just an extra question: We use calcium hypochlorite and trichlor. Pool guy says that if the calcium hypochlorite smells too strong, it is because it is Chinese and it doesn't work, and that high quality calcium hypochlorite and trichlor have virtually no smell. Is that true?

    Thanks in advance.

  2. Back To Top    #2
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Tucson, AZ

    Re: Theory vs Practice

    Your pool guy has no idea what he is talking about ... the only thing that smells is CC if there is something in your pool.

    Our recommendations will work in 99.9% of the pools out there. It is certainly possible to keep a clear pool by not following the levels we recommend if you happen to have special circumstances.

    BTW the minimum for a SWG pool with a CYA of 100ppm is 5ppm (not 7ppm).
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  3. Back To Top    #3
    Mod Squad woodyp's Avatar
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    Apr 2010
    East Texas

    Re: Theory vs Practice

    Please tell me where on that chart it says that concerning your FC level.. And we're certainly not here to argue with you over your "happiness level" with your pool guy. If it's working for you----------Enjoy!
    When it doesn't---------we'll still be here. Maybe your pool guy would enjoy spending some time in Pool School here----just in case.
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  4. Back To Top    #4
    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: Theory vs Practice

    I see pH being a bit low for eye comfort and CYA being a bit high, but otherwise things agree with
    If there's any metals in the water, a low pH will help keep them in suspension.

    If you have a SWG and high CYA, why would you need to use calcium hypochlorite and trichlor? The SWG ought to be able to keep up with the demand.

    Frequent backwashing just wastes water, but doesn't harm the filters. Is it any different than washing a towel every day rather than once a week or whatever? Backwashing will help to keep that CYA from getting any higher from the trichlor usage.

    Can't comment on Chinese chemicals. I use bleach mostly, or premium pucks when I'm on vacation. I never smell chlorine or anything else. It wouldn't surprise me if cheap chemicals smell, though.
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  5. Back To Top    #5

    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Theory vs Practice

    We never, ever, said that if your FC level gets below the minimum for the CYA level that algae will definitely grow. Algae growth depends on other factors including the presence of algae nutrients, the amount of sunlight, the temperature, and any inhibiting chemicals such as algicides. The FC/CYA chart is what works for nearly all pools (with decent circulation) to prevent green and black algae growth regardless of these factors -- that is, regardless of the phosphate or nitrate level or amount of sunlight or water temperature.

    As for needing to clean the filter every other day, that shouldn't be necessary unless there is a lot of debris getting into the pool, but you said the pressure wasn't rising so that doesn't make sense. Also, since when does a pool guy visit pools every other day? That also seems strange (assuming you are talking about residential pools).
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    Mod Squad Patrick_B's Avatar
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    Jun 2011

    Re: Theory vs Practice

    It sounds like a facility of some sort where a guy is there daily?

    I agree, something isn't right about that back washing every other day, or there will be turbidity.
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