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Thread: Partial fill help

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    Partial fill help

    hi all! okay, after a year of love/hate relationship with the pool, i'm ready to make the effort to turn this into only a loving relationship! Since the day we took ownership of our house/pool, the cya was always 100+. I'm guessing now that it was well over 100, and this obviously caused problems. We also inherited some mustard algae that i'm thinking was hiding out in the 50 degree water and showed up as things got warmer last year. I spent a lot of time and wasted plenty of chlorine 'shocking' the pool, keeping things fairly clean for a week or so until the algae would return. This would repeat all summer long with the problem being those 'shocks' never got close to shock level with our cya being so high.

    Wanting to avoid this cycle again, i bit the bullet and drained approximately 40-50% of the pool yesterday. It finished filling early this morning and i checked the numbers about 2 hours after that. Here they are (~25k gallons):

    fc = 0.5
    ph = 8.2
    ta = 150
    ch = 300
    cya = 80

    I was hoping the cya was going to end up around 50-60 but oh well. At least i know the number now and i can work with that. I was also hoping ta and ph were going to be lower but this can be dealt with. What i'd appreciate is some input on my course of action now. Ultimately, my goal is to shock and rid the pool of all algae. I also know the ph needs to be lowered and i'm guessing ta as well, but should that be done prior to shocking? Can it be done while i'm shocking? after? If we want to start using the pool soon, would i be okay to frequently add acid to maintain a lower ph and hope the ta drifts down over time, or should i lower ph and aerate? anything else i need to address? I appreciate the help!!! thanks
    ~25k gallon plaster in ground pool - solar panel heater - pentair pump and filter

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Partial fill help

    Definitely bring PH down to around 7.2 as soon as possible, before doing anything else. After that, just keep lowering PH to 7.2 any time it gets to 7.8 and repeat as long as the TA is too high.

    Once you have done that you can start shocking the pool any time. Remember that high FC levels invalidate the PH test results, so don't worry about PH during shocking.
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    Mod Squad woodyp's Avatar
    Join Date
    Apr 2010
    East Texas

    Re: Partial fill help

    That level of CYa is gonna be fun to deal with while shocking unless it is needed for a SWCG after shocking if you have one. Lower PH first. Shock it normally first. Then proceed to shock level for mustard algae. Total process is in pool school.
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    Re: Partial fill help

    exactly what i needed to hear, thanks Jason! I didn't know high FC invalidates PH test results, very good to know.

    Yeah, i know cya of 80 is gonna be fun and costly (no SWCG), but it's way better than what must have been about 150 =( thanks for reminding me i need to shock normally first! i had read that and it didn't stick in my mind.
    ~25k gallon plaster in ground pool - solar panel heater - pentair pump and filter

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    Re: Partial fill help

    ok, so i have addressed ph and am now ready to work on the chlorine =) however, i have a question before i start. I have 8 bags of 68% Calcium Hypochlorite pool shock sitting in the garage. Am i okay to use these in conjunction with 6% bleach this round of shocking? Using the pool calculator, it looks like each 1lb bag has the same effect on the water as 182oz of 6% bleach. Seems like i should be fine doing this? thanks
    ~25k gallon plaster in ground pool - solar panel heater - pentair pump and filter

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    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    SouthWest Alabama

    Re: Partial fill help

    With a CH of 300 I wouldn't use too many of them. It's fine to use some, but you don't want your CH getting too high. The Pool calc will let you know how much each bag will add so you can figure how many it's safe to use.
    Dave J. TFP Moderator
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    Re: Partial fill help

    doh! totally forgot to use that tool on the pool calc. thanks!!!
    ~25k gallon plaster in ground pool - solar panel heater - pentair pump and filter

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