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Thread: Calcium hardness low -- buy granular shock, or wait?

  1. Back To Top    #1

    Join Date
    Jun 2008
    Location
    Prescott, Wisconsin
    Posts
    220

    Calcium hardness low -- buy granular shock, or wait?

    I just opened my pool, added liquid chlorine, and tested the water:

    FC: .4 (Don't worry, I'm planning to add chlorine!)
    CC: 0
    pH: 7.4
    TA: 100
    CH: 140
    CYA: <25
    Sat: -.4
    Temp: 70F

    My questions are:
    1) Should I throw in some granular shock, to raise my Calcium Hardness? I'd have to go buy some, which is easy enough to do. But maybe as I add tap water over the summer, CH will go up on it's own? I don't want to buy granular shock if I don't have to!
    2) I have a bunch of chlorine/stabilizer pucks left over -- should I start using them to add CYA to my water?
    3) Any need to adjust the saturation? I know it's within the limits, but I worry.
    4) Does 70F water have any effect on these readings?

    Thanks for your expert help!
    -----------------------------------
    26000 gal, in-ground, vinyl pool
    Hayward S200 sand filter, 1 skimmer, 2 returns
    BBB since the first month! :-)

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,887

    Re: Calcium hardness low -- buy granular shock, or wait?

    You have a vinyl liner pool, so you don't have any reason to add calcium (except possibly meeting warranty terms). Likewise, you want to run with a very low saturation index.

    Your CYA is low. You can use trichlor/dichlor to raise CYA, but it will take a while.
    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

  3. Back To Top    #3

    Join Date
    Jun 2008
    Location
    Prescott, Wisconsin
    Posts
    220

    Re: Calcium hardness low -- buy granular shock, or wait?

    I'm relieved that I don't have to worry about those things. I've never raised CYA ... can I buy it cyanuric acid somewhere?
    -----------------------------------
    26000 gal, in-ground, vinyl pool
    Hayward S200 sand filter, 1 skimmer, 2 returns
    BBB since the first month! :-)

  4. Back To Top    #4

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

    Re: Calcium hardness low -- buy granular shock, or wait?

    You can purchase CYA at any pool store. Many folks here get theirs at Wal-Mart, although my Wal-Mart never has any.

    Like Jason said though, there is no harm in using stabilized chlorine sources such as dichlor or trichlor if you have them on hand. Just remember that dichlor adds CYA quite rapidly. In either case, as long as you are aware that they both add CYA and you stay on top of their addition to ensure that you don't end up with too high of a CYA level, you'll be fine.
    10K gallon IG gunite with waterfall; Pentair CC320P filter; WhisperFlo 2 HP pump
    TF Test Kits - Pool Math - Pool School
    "It depends."- JohnT

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